Search

With the rapid development of urbanization, ambient air pollution is becoming increasingly serious. Out of many pollutants, fine particulate matter (PM2.5) is the pollutant that affects the urban atmospheric environment to the greatest extent. Fine particulate matter (PM2.5) concentration prediction is of great significance to human health and environmental protection. This paper proposes a CNN-SSA-DBiLSTM-attention deep learning fusion model. This paper took the meteorological observation data and pollutant data from eight stations in Bijie from 1 January 2015 to 31 December 2022 as the sample data for training and testing. For the obtained data, the missing values and the data obtained from the correlation analysis performed were first processed. Secondly, a convolutional neural network (CNN) was used for the feature selection. DBILSTM was then used to establish a network model for the relationship between the input and actual output sequences, and an attention mechanism was added to enhance the impact of the relevant information. The number of units in the DBILSTM and the epoch of the whole network were optimized using the sparrow search algorithm (SSA), and the predicted value was the output after optimization. This paper predicts the concentration of PM2.5 in different time spans and seasons, and makes a comparison with the CNN-DBILSTM, BILSTM, and LSTM models. The results show that the CNN-SSA-DBiLSTM-attention model had the best prediction effect, and its accuracy improved with the increasing prediction time span. The coefficient of determination (R2) is stable at about 0.95. The results revealed that the proposed CNN-SSA-DBiLSTM-attention ensemble framework is a reliable and accurate method, and verifies the research results of this paper in regard to the prediction of PM2.5 concentration. This research has important implications for human health and environmental protection. The proposed method could inspire researchers to develop even more effective methods for atmospheric environment pollution modeling. [ABSTRACT FROM AUTHOR]

A companding method for peak-to-average power ratio (PAPR) reduction in optical orthogonal frequency division multiplexing systems has been proposed and simulated. The proposed scheme is based on the modified hyperbolic tangent transform, which can enlarge the small signals and compress the large signals while keeping the average power invariant. Simulation results verify that the proposed companding scheme can markedly decrease the PAPR, and a good bit error rate performance is obtained. [ABSTRACT FROM AUTHOR]

In order to emit a linearly polarized light and reduce energy loss for a white light emitting diode (LED), a multilayer metal-dielectric grating structure using GaN-based blue LED is proposed. This multilayer structure is composed of three major functional layers: a fluorescent ceramics layer, a dielectric anti-reflection layer and a linear polarization grating layer. Fluorescent ceramics layer is integrated on the top of GaN-based blue LED, to achieve white light emission. In turn, a dielectric anti-reflection layer and a linear polarization grating layer are also integrated to obtain a higher transmission of white light and improve the conversion efficiency of linear polarization. The structural parameters of each functional layer, including period (150 nm), duty cycle (0.5), height of metal-dielectric grating (55 nm and 80 nm) and thickness of dielectric layer (15 nm), are simulated and optimized by finite-difference time-domain method. Then the multilayer structure is fabricated by UV nanoimprint and its transmission and polarization characteristics are tested. The results show that the transmittance and extinction ratio are higher than 50% and 33.8 dB in the wavelength range of 400–800 nm, and the maximum value can reach 91.3% and 41.3 dB, respectively. It is well verified by experiments that the proposed structure has a steady polarization performance of TM mode in the range of ±20°, which provides a fundamental guarantee for developing the potential applications of polarized white LED. • A multilayer metal-dielectric grating structure is proposed to obtain the highly linearly polarized white light. This multilayer structure is composed of three major functional layers: a fluorescent ceramics layer, a dielectric anti-reflection layer and a linear polarization grating layer. • The structural parameters of each functional layer, including period (150 nm), duty cycle (0.5), height of metal-dielectric grating (55 nm and 80 nm) and thickness of dielectric anti-reflection layer (15 nm), are simulated and optimized by finite-difference time-domain method. Theoretical results show that the maximum value of the transmittance and extinction ratio can reach 91.3% and 41.3 dB in the wavelength range of 400–800 nm, respectively. • The UV nanoimprint technology is used to fabricate the proposed multilayer metal-dielectric grating structure, and its transmission and polarization characteristics are tested. The experimental results show that the transmittance and extinction ratio are higher than 50% and 33.8 dB in 0–20° incident angle range. • This structure of linearly polarized white light with high T and ER can be well used in LCD backlight to improve the contrast and brightness of display screen while reducing energy consumption, as well as many potential applications. [ABSTRACT FROM AUTHOR]

In the art museum, lighting plays a crucial role in visitors' understanding and appreciation of exhibits. This paper mainly explores the influence of different lighting mode (general lighting, accent lighting, and mixed lighting) and correlated color temperature (CCTs) (4000 K and 2700 K) changes on the observers' psychology to find the best lighting environment. Based on the simulation carried out at the National Museum of Western Art in Japan, we made six diverse lighting designs. 31 observers were invited to evaluate each scheme, and the results of subjective evaluation were analyzed by means of one-way analysis of variance and the paired sample T-test. According to the results of data analysis, suggestions can be given for art gallery lighting design. It is not recommended to use general lighting alone in art museums, and it is better to use mixed lighting. When the CCT is 4000 K, only accent lighting can be used. When the CCT is 2700 K, the mixed lighting effect is better. [ABSTRACT FROM AUTHOR]

Highlights • A partial feedback closed loop controller for daylight harvesting with LED. • Economically calculating quantity of electric light to compensate illuminance. • Low computation cost and parameter tuning free. Abstract The indoor energy management of lighting is essential for the construction of a smart city; a lighting system that dims electric lights based on the daylight level helps in energy conservation. One of the most common methods to achieve such daylight control is to measure the combination of daylight and electric light, and to determine the dimming level of the electric light. Based on the PWM dimming principle, we present a low computation cost and partial-feedback closed loop control scheme for LEDs, which only measures and feedbacks the contribution of daylight, not that of both light levels, to determine the output of the electric light. Using the photo sensor TEMT6000, a prototype is presented to verify the partial feedback scheme. Experiments show that the partial feedback controller has the capability to stabilize illuminance satisfactorily. [ABSTRACT FROM AUTHOR]

Abstract The photoluminescence properties and formation mechanism of oxygen vacancies in Ca 4 (PO 4) 2 O crystal were studied. X-ray diffraction, photoluminescence spectra, and Fourier transform-infrared spectra were used to investigate the formation process of Ca 4 (PO 4) 2 O crystal. Pure Ca 4 (PO 4) 2 O crystal prepared in reducing atmosphere shows an intense emission at 405 nm under excitation of 330 nm, which is originated from oxygen vacancies in the lattice. It can be concluded that oxygen vacancies in Ca 4 (PO 4) 2 O crystal exhibit a high thermal stability and the strong photoluminescence emission can be observed for the sample recalcined in air at 400 °C. The results of XRD and FTIR indicate a phase transformation process between Ca 4 (PO 4) 2 O, Ca 10 (PO 4) 6 O and Ca 10 (PO 4) 6 (OH) 2 phase and oxygen vacancies are also formed during this process. Furthermore, a novel Eu2+ singly doped phosphate phosphor with multi-color emission can be firstly developed through strictly controlling phase transformation of the host. Under NUV excitation, the color coordinates are calculated to be (0.3427, 0.3229) and (0.3872, 0.3429) closely corresponding to white/warm white light. The warm white light with high color rendering index (R a : 87.6) and low correlated color temperature (3510 K) can be achieved based on the Eu2+ singly doped phosphate phosphor. [ABSTRACT FROM AUTHOR]

A series of Ce 3+ /Tb 3+ doped α-Ba 3 Y(BO 3 ) 3 phosphor has been synthesized by a conventional solid state method. The crystal structure and luminescence properties, specifically the energy transfer behavior were investigated. Result shows that all phosphors have pure phase confirmed by XRD and morphology. Under ultraviolet (UV) or near-UV excitations, the α-Ba 3 Y(BO 3 ) 3 :Ce 3+ phosphors showed a blue emission of Ce 3+ (5d→4f) at 356 and 396 nm and the α-Ba 3 Y(BO 3 ) 3 :Tb 3+ phosphors mainly exhibited a green emission of Tb 3+ at 542 and 550 nm ( 5 D 4 → 7 F 5 ), respectively. The energy transfer process was investigated between Ce 3+ and Tb 3+ ions by the wide spectral overlap of Ce 3+ emission spectrum and Tb 3+ excitation spectrum. The efficient energy transfer from Ce 3+ to Tb 3+ ions was studied by different Tb 3+ concentration in α-Ba 3 Y(BO 3 ) 3 :Ce 3+ , x Tb 3+ phosphors. The critical distance was calculated and the ET mechanism was determined to vary from dipole-dipole interaction to dipole-quadrupole interaction while Tb 3+ concentration exceeded 0.1. The CIE color coordinates were listed for all prepared samples. So, all these results indicate that the as-synthesized green phosphor α-Ba 3 Y(BO 3 ) 3 :Ce 3+ ,Tb 3+ has potential applications for ultraviolet LEDs and displays. [ABSTRACT FROM AUTHOR]

Fluctuation of current through alternating current operated light-emitting diodes (AC LEDs) make luminous flux simply equivalent to the product of power consumption and luminous efficiency unreasonable, unlike constant current scenario. Based on application model and average luminous efficiency introduced by this paper, relationship between AC LEDs luminous flux and its application circuit parameters, including balance resistor, threshold voltage and equivalent resistor of LED etc. was presented. Then method to design AC LEDs through single LED photoelectric characters to meet luminous flux requirement was given. [ABSTRACT FROM AUTHOR]

Abstract: The basic concept of daylight perceptive is that the artificial light automatically dims to the appropriate level to keep constant indoor illumination when sufficient daylight is not available. Energy efficient character of daylight perceptive lighting was analyzed and a method to evaluate energy saving was present; according to the presentation, the more energy is saved if the longer T last—duration of indoor illumination being is less than threshold. A daylight perceptive controller was developed and the output power of LED light source under different PWM was measured, according to the measurement, work current and output power of LED is proportional to duty cycle. With two sensors, a data fusion method was put forward to exclude interference and improve lighting comfort. With more than two sensors, data fusion based on neutral network was discussed. [Copyright &y& Elsevier]

The article presents a study which examines the efficiency of a highly nonlinear octagonal photonic crystal fiber (HN-OPCF) with Germanium (Ge)-doped core for use in optical coherence tomography (OCT). The study performs simulations for two HN-OPCF with high nonlinear coefficient and flattened dispersion at 1.31µm wavelength bands. Result shows high nonlinear coefficient and flattened dispersion of HN-OPCF, which can enable supercontinuum generation, which is critical in OCT.

Abstract: This paper reveals a novel dispersion compensating photonic crystal fiber (DC-PCF) for wide-band high-speed transmission systems. The finite-difference method with an anisotropic perfectly matched absorbing layers boundary condition is used to investigate the guiding properties. The designed novel DC-PCF shows that it is possible to obtain a larger negative dispersion coefficient, better dispersion slope compensation, and confinement losses less than 10−4 dB/m in the entire S+C+L telecommunication band by using a modest number of design parameters. The proposed module can be used in 40Gb/s dense wavelength division multiplexing (DWDM) systems in optical fiber communication networks. [Copyright &y& Elsevier]

Abstract: The present article describes novel highly nonlinear photonic crystal fibers (HN-PCFs) with flattened chromatic dispersion and low confinement losses. The proposed design has been simulated based on the finite-difference method with anisotropic perfectly matched layers absorbing boundary condition. It is proved that the design novel HN-PCFs is obtained a nonlinear coefficient greater than 45W−1 km−1 and low dispersion slope −0.009ps/(nm2.km) at 1.55μm wavelength. In addition, results from numerical simulation show that the ultra-flattened dispersion of 0±0.65ps/(nm.km) can be obtained in a 1.36–1.62μm wavelength range with confinement losses lower than 10−7 dB/m in the same wavelength range. Another advantage of the proposed HN-PCFs is that it possessed modest number of design parameters. [Copyright &y& Elsevier]

The article presents a study on the identification of an ultra-flattened chromatic diffusion in index-guiding square photonic crystal fibers (SPCFs). The study compares the properties of the two-different-size hole-arrayed SPCFs and three hexagonal photonic crystal fibers (HPCFs) design considering the ultra-flattened diffusion range, efficient area, number of design parameters, and the confinement loss. Conclusion notes that the proposed SPCFs demonstrate reasonable dispersion tolerance.

The article presents a study on the unique approach in ultra-flattened dispersion photonic crystal fibers (PCF) that contains elliptical air-holes. It involves the introduction of two rings of elliptical air-holes that is disposed perpendicular alternately. The study proves that it is possible to control chromatic dispersion of index guiding PCFs in wide wavelength range through the arrangement of major axis of the first inner ring perpendicular to that of the second ring.

Illuminance estimation is key to daylight responsive lighting, and accurate estimation of illumination on workplane requires multi-point illumination, which requires distributed measurement techniques. With as few technical components as possible, we present a lightweight solution of distributed illuminance measurement to accelerate system development. Based on the open source technology, Arduino, we develop porotype of the system, including sensing unit, clock unit and storage unit, without communicating unit different from common distributed measurement. We construct device to calibrate sensing unit with three kind of correctors, and compare the difference of the measurements. Based on absolute time synchronization, we synchronize illuminance by the specified time according to the measurement interval. We carry out the experiments on illuminance estimation to verify that it cannot be completely solved with one single illuminance ratio, although it works well under some specific circumstance. [ABSTRACT FROM AUTHOR]

Illuminance estimation is key to daylight responsive lighting, and accurate estimation of illumination on workplane requires multi-point illumination, which requires distributed measurement techniques. With as few technical components as possible, we present a lightweight solution of distributed illuminance measurement to accelerate system development. Based on the open source technology, Arduino, we develop porotype of the system, including sensing unit, clock unit and storage unit, without communicating unit different from common distributed measurement. We construct device to calibrate sensing unit with three kind of correctors, and compare the difference of the measurements. Based on absolute time synchronization, we synchronize illuminance by the specified time according to the measurement interval. We carry out the experiments on illuminance estimation to verify that it cannot be completely solved with one single illuminance ratio, although it works well under some specific circumstance. [ABSTRACT FROM AUTHOR]

The comfortable office lighting is one of the important issues for people's health and working efficiency. In this paper, the current lighting situation of the office was measured and analyzed. We built an office model with the Rhino software to simulate the daylight environment and calculated the glare with the DIVA plug-in. The results show that the daylight glare is more serious in January, February, November, and December. Try to block out part of the sun to avoid glare in these months and use artificial lighting instead. We used DIALux evo to make an office model to simulate light environment. The lighting environment of the office area was optimized by changing the parameters of the light source and the position of the lamp. The optimal light environment is more energy saving and comfortable. [ABSTRACT FROM AUTHOR]

A series of Dy3+/Sm3+ co-doped KZnPO 4 phosphors were synthesized by the conventional solid-state reaction method. The crystal structure, luminescent characteristic and lifetime were studied by X-ray diffraction, photoluminescence properties and decay life. Dy3+/Sm3+ co-doped and Sm3+ doped KZnPO 4 phosphors exhibited high crystallinity in structure from XRD results. Under the ultraviolet (UV) or near-ultraviolet (NUV) excitation, KZnPO 4 : Dy3+, Sm3+ phosphors emitted adjustable color coordinates light by changing the content of Sm3+ ions, which indicated the phosphors might be of potential application in display and lighting. The optimum Sm3+ concentration is 0.005. Furthermore, energy transfer from Dy3+ to Sm3+ was confirmed by the emission spectra and the decay time of co-doped phosphors. [ABSTRACT FROM AUTHOR]

As far as taking-away of the symmetry constraints is concerned, as a scientifically symmetry problem, the global synthesis for antenna arrays that produce the desired radiation pattern is also a highly nonlinear optimization issue in fact. Besides this, the built criteria offer the reasonable power patterns. The consequent synthesis could be implemented by looking for a nominal pattern. When the criteria are already sufficient, it can simply do the whole synthesis process. To utilize multiple antennae, a method to choose a transmit antenna for the linear dispersion codes (LDC-TAS) is implemented in this paper. The authors used the max–min-post- signal to noise ratio (SNR) criteria to select these optimal transmitting antennae while this dependent, linear receiver is applied to the varying and slow channel. The simulated results illustrate that this max–min-post-SNR criterion outperforms the Bell Labs layered space time transmitting antenna selection (BLAST-TAS) applying the same spectral efficiency than space–time block codes (STBC)-TAS in the environment with low SNR. Furthermore, once the M antennae are selected under the selection criteria, a max–min-post-SNR rule, a novel linear antenna synthesis to linear dispersion codes on the basis of an innovative HYBRID (of mixed characters or solutions) genetic algorithm has been presented and evaluated to formulate and address the optimal problem to non-uniformly spaced and linear arrays. The restricted side-lobes level, the main-lobe width, and the shaped beam pattern are contemporarily concerned via maximizing a pretty suitable cost function through the innovational advanced genetic-algorithm-based algorithm. The method proposed in this paper can provide flexibility and a simple insertion of the a priori knowledge under a small computing pressure. At last, a computing simulation is completed well and the results are shown. It should be noticed that some extensions of the presented method could also be easily utilized without an obvious increase in the algorithm complexity. [ABSTRACT FROM AUTHOR]

With the development of modern society, there are not only many voice calls being made over wireless communication systems, but there is also a great deal of demand for data services. There are increasing demands from the general public for more information data, especially for high-speed services with elevated Gbps levels. As is well known, higher sending power is needed once data rates increase. In order to solve this problem, virtual cellular networks (VCNs) can be employed in order to reduce these peak power shifts. If a VCN works well, mobile ports will receive their own wireless signals via individual cells, and then, the signals will access core networks with the help of a central terminal. Power control can improve the power capacity in multi-hop networks. However, the use of power control will also have a negative impact on network connectivity, delay, and capacity. In order to address the problem, this paper compares specific control methods and capacities in multi-hop networks. Distributed chicken game algorithm power control (DCGAPC) methods are presented in order to reach acceptable minimum levels of network delay and maximum network capacity and connectivity. Finally, a computer simulation is implemented, and the results are shown. [ABSTRACT FROM AUTHOR]

The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air.The green-emitting SrSi2O2N2:Eu2+ phosphors with single phase have been successfully synthesized by a simple two-step method. During the first-step process, Sr2SiO4:Eu3+ precursor was formed and emitted red light under UV light excitation. The excessive amount of Si3N4 in reactants promoted the formation of pure SrSi2O2N2 phase when molar ratio of Si3N4/Sr2SiO4 was located in the range of 1.1–1.5. The luminescence intensities of SrSi2O2N2:Eu2+ phosphors were enhanced by Si3N4/Sr2SiO4 molar ratio of 1.1. Phase analysis, luminescence properties and thermal stability of the samples were intensively investigated by X-ray diffraction, SEM, XPS and TGA/DSC. The trivalent europium ions were identified by XPS results on the surface of as-synthesized SrSi2O2N2:Eu2+ particles with approximate theoretical atomic ratio of Eu/Sr, which prevent the further oxidation of Eu2+ to Eu3+ in the bulk structure and evidently improved the thermal stability of the phosphors. For the thermal oxidation mechanism, it was suggested that the oxidation of SrSi2O2N2 to form SrSiO3 layer firstly occurred on the surface after a calcination process in air. [ABSTRACT FROM AUTHOR]