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The development of novel white-light-emission phosphors is of great importance for applications in lighting and display fields. Trivalent Dy3+ is widely used as a potential luminescence center for white-light emission. However, Dy3+-doped phosphors often suffer a poor yellow to blue ratio due to the deficiency of its 4F9/2 → 6H15/2 transition, low luminescence efficiency, and unsatisfactory thermal stability. The importance of the present research work is that we have achieved a tunable white light in a single phased stannate phosphor Sr3Al10SnO20:Dy3+ with robust thermal stability. The crystal structure, phase purity, and chemical composition were investigated via X-ray diffraction Rietveld structure refinement, scanning electron microscopy, and energy dispersive spectrometry. The luminescence spectra indicated that Sr3Al10SnO20:Dy3+ not only exhibited characteristic 4F9/2 → 6HJ/2 (J=11, 13, and 15) inherent transition emissions of Dy3+, but also showed an abnormal blue band emission, which was identified through X-ray photoelectric spectroscopy as the T1 → S0 transitions of Sn2+, resulting from the valence variation of Sn4+. The efficient energy transfer from Sn2+ to Dy3+ was also confirmed and the transfer efficiency was calculated. Owing to the valence-variation-induced emission of Sn2+, a tunable white light could be realized from a cool to warm white light region, with Commission Internationale de l'Eclairage coordinates and a correlative color temperature varying from (0.277, 0.333) and 8634 K to (0.353, 0.404) and 4913 K, respectively. The luminescent and defects formation mechanism as well as the luminescence kinetics were further investigated. Moreover, Sr3Al10SnO20:Dy3+ had a high quantum efficiency (∼34.6%) and a super-stable thermal stability behavior (82.5% at 240 °C of the initial integral emission intensity at 30 °C) with a large activation energy (ΔE ∼ 0.1654 eV). Finally, a charge-compensation test was performed to further verify the effect of defects on the luminescence property and the related mechanism was discussed. The current work provides a novel method to achieve tunable white-light emission in Dy3+ single-doped phosphors and the related mechanism is effectual for other rare earths for potential applications in lighting and display fields. [ABSTRACT FROM AUTHOR]

Abstract A series of new red emission phosphors Ca 7 Zn 2 (PO 4) 6 : Re3+ (Re3+ = Eu3+, Sm3+, Pr3+) are synthesized by solid state reaction. The crystal structure and microstructure are systematically investigated by X-ray diffraction Rietveld structure refinement, scanning electron microscopy and energy dispersive spectrometer. The photoluminescence properties of Ca 7 Zn 2 (PO 4) 6 : Re3+ (Re3+ = Eu3+, Sm3+, Pr3+) are studied in detail. The results show that Eu3+, Sm3+ or Pr3+ single doped Ca 7 Zn 2 (PO 4) 6 could emit red emissions with dominate peaks at 612 nm, 602 nm and 612 nm, respectively, which are attributed to the characteristic transitions (5D 0 -7F 2 , 4G 5/2 -6H 7/2 and 3P 0 -3H 6) of Eu3+, Sm3+ and Pr3+. The concentration dependent emission spectra of Ca 7 Zn 2 (PO 4) 6 : Sm3+ are studied as well. A charge compensator Li 2 CO 3 is added in Sm3+ doped Ca 7 Zn 2 (PO 4) 6 and the emission intensity is compared with the commercial red phosphor Y 2 O 3 :Eu3+. The room temperature fluorescence lifetimes of Ca 7 Zn 2 (PO 4) 6 : Re3+ (Re3+ = Eu3+, Sm3+, Pr3+) are measured and the average lifetimes are evaluated. Finally, the Commission Internationale de L'Eclairage chromaticity coordinates and their color purity are calculated. Graphical abstract Image 1062 Highlights • Novel red emission phosphors CZP: Re3+ were synthesized for the first time. • Phase purity and microstructure were examined by XRD, SEM and EDS. • Characteristic luminescent property of CZP: Re3+ was investigated. • The detailed emission property of CZP:Sm3+ and CZP:Sm3+, Li+ was studied. • Decay behavior, CIE and color purity of CZP: Re3+ were investigated. [ABSTRACT FROM AUTHOR]

To explore a new family of phosphate phosphors for application in ultraviolet-based light emitting diodes (LEDs), novel promising blue emission solid solution phosphors, Ca1−xSrxHf4(PO4)6:Eu2+, with efficient and controllable photoluminescence were synthesized and characterized in the full range of 0 ≤x≤ 1. To deeply understand the relationship between the structure and properties of the phosphors, the phase purities, crystal structures and linear structural evolutions of Ca1−xSrxHf4(PO4)6:Eu2+ solid solutions were investigated in detail by FT-IR spectroscopy and Rietveld structure refinement of their powder XRD patterns and verified by high transmission electron microscopy (HRTEM). The linear structural evolutions induced controllable blue emission with high quantum efficiency and excellent thermal stability in the Ca1−xSrxHf4(PO4)6:Eu2+ solid-solution phosphors. Moreover, the photoluminescence properties in Ca1−xSrxHf4(PO4)6:Eu2+ can be optimized by adjusting the components. The mechanism of the controllable luminescence properties was also investigated in detail. Excellent thermal stability was obtained in Ca1−xSrxHf4(PO4)6:Eu2+, and the thermal quenching mechanism was investigated. Finally, white LEDs were fabricated and their electroluminescence properties were investigated. This simple and effective method to optimize the photoluminescence properties of phosphors can be used for designing other novel solid-solution phosphors. [ABSTRACT FROM AUTHOR]

A series of versatile phosphors Sr 10 [(PO 4 ) 5.5 (BO 4 ) 0.5 ](BO 2 ):Sb 3+ /Eu 3+ /Pr 3+ /Dy 3+ were firstly synthesized by solid-state method. The phase purity was analyzed through X-ray diffraction and their characteristic luminescence properties were investigated. The results showed that Sr 10 [(PO 4 ) 5.5 (BO 4 ) 0.5 ](BO 2 ): Sb 3+ exhibited broad blue emission centered at 459 and 467 nm, due to the selective excitation transitions ( 3 P 1/0 → 1 S 0 ) of Sb 3+ occupying different crystal sites in Sr 10 [(PO 4 ) 5.5 (BO 4 ) 0.5 ](BO 2 ). The emission spectrum of Sr 10 [(PO 4 ) 5.5 (BO 4 ) 0.5 ](BO 2 ): Eu 3+ consisted of a series of lines attributed to the 5 D 0 → 7 F J ( J =1, 2, 3, 4) transitions of Eu 3+ . Moreover, an unusual blue emission band was observed, which was discussed in detail and proved to be related to the vacancy of Sr 2+ through the charge compensation mechanism. In addition, red and warm white emissions could be obtained from Pr 3+ and Dy 3+ single doped Sr 10 [(PO 4 ) 5.5 (BO 4 ) 0.5 ](BO 2 ) and their luminescence properties were discussed, respectively. [ABSTRACT FROM AUTHOR]

A novel Pr 3+ ions doped red phosphor Ca 19 Mg 2 (PO 4 ) 14 :Pr 3+ was first synthesized and the phase purity as well as the characteristic photoluminescence property was investigated through X-ray diffraction, diffuse-reflectance and photoluminescence spectra measurement. The analysis revealed that Ca 19 Mg 2 (PO 4 ) 14 :Pr 3+ had strong absorption from 450 to 470 nm and could exhibit red emission peaking around 610 nm under 450 nm excitation. The emission quenching behavior of 1 D 2 – 3 H 4 transitions via increasing the Pr 3+ contents was investigated and the mechanism was discussed in detail. The temperature dependent emission spectra of Ca 19 Mg 2 (PO 4 ) 14 : x Pr 3+ with different doping contents ( x =0.002 and x =0.02) were studied and the abnormal thermal quenching property was investigated. [ABSTRACT FROM AUTHOR]

A novel phosphate RbZnPO4 has been developed for the first time and the characteristic crystal structure of RbZnPO4 has been investigated in detail, based on the Fourier transform infrared reflection spectra and the structure refinement of X-ray diffraction data. After doping with Eu3+,RbZnPO4:Eu3+ shows distinctive deep red emission with dominating peaks at 596 and 701 nm. To provide a reasonable explanation for the relationship between photoluminescence and structure, the photoluminescence property has been discussed by analyzing the particular local ligand environment and site occupation of Eu3+ in RbZnPO4. More interestingly, temperature-sensitive emission behavior was found in RbZnPO4:Eu3+. Through the synthetical analysis of the configurational coordinate diagram, the charge compensation experiment and the CASTEP band structure calculation, a complex underlying mechanism is proposed to explain the abnormal temperature-sensitive emission behavior in RbZnPO4:Eu3+. The mechanism could be helpful for better understanding the thermal quenching process of Eu3+ in RbZnPO4 and also as a reference in some other temperature-sensitive phosphors. [ABSTRACT FROM AUTHOR]

Abstract: The photoluminescence properties of mono Ce3+ doped Sr5(PO4)2SiO4 (SPS) apatite phosphors, prepared via a solid-state reaction at high temperature, were investigated in the ultraviolet region. The white light can be realized by adjusting the contents of activator Ce3+ or the excitation wavelength. Upon 365nm excitation, SPS: 0.05Ce3+ shows bright white light (34.74% of YAG) with CIE color coordinates of (0.33, 0.34), a superior color-rendering index of 90 and correlated color temperature of 5603K, suitable for potential use based on 365nm UV-InGaN chip. [Copyright &y& Elsevier]

The burgeoning phosphor‐converted near‐infrared light‐emitting diodes (pc‐NIR LEDs) have important applications in special illumination and spectroscopy analysis. However, the development of efficient NIR‐emitting phosphors with high performance is still a challenge. In this work, a chemical unit co‐substitution strategy is proposed to realize the excitation transition regulation and successfully achieve high‐performance NIR luminescence in Ca3‐yNayMg1‐ySb2‐xAl2+yO12: xCr3+ (0 ≤ x ≤ 0.05, 0 ≤ y ≤ 1) garnet‐type solid solution phosphors. Through the excitation transition modulation from the 4A2 ground state to the 4T1(4P) and 4T1(4F) excitation state, the excitation intensity at the blue light region is largely enhanced by 25.6 times. Moreover, the NIR‐emitting efficiency and thermal stability are improved, with the optimal luminescence internal quantum efficiency of 90.6% and thermal stability of 97%@423 K, without any flux‐assisted sintering or reduction atmosphere protection. The structure regulation induced small Stokes shift, weak electron‐phonon coupling effect, and decreased non‐radiative transition are responsible for the excellent NIR‐emitting performance. Finally, the NIR pc‐LED is fabricated with photoelectric efficiencies of 18.7%@100 mA and NIR output powers of 63 mW@100 mA, presenting potential applications in nondestructive internal defect detection, veins imaging, and night vision surveillance. [ABSTRACT FROM AUTHOR]

With the development of solid-state lighting, full-spectrum lighting has gradually received extensive attention. Until now, Bi3+-doped narrow-band blue phosphors have been widely reported, but broadband green-yellow Bi3+-doped luminescent materials generated by metal-to-metal charge transfer have been rarely reported. In this study, a Bi3+ ion doped germanate luminescent material CsAlGe2O6:x%Bi3+ (1 ≤ x ≤ 11) is synthesized by a high-temperature sintering method. The phosphor can generate a broad green-yellow band peaking at 535 nm with a full width at half maximum of 165 nm under ultraviolet radiation. Through the analysis of the coordination environment, photoluminescence spectra and decay curves, the broadband emission spectra of Bi3+ ions are proved to be generated by the metal-to-metal charge transfer state and the 3P1 → 1S0 transition. By using theoretical research, luminescence kinetics, and Gaussian fitting, the luminescence mechanism of Bi3+ is examined. Meanwhile, the high quantum efficiency and superior thermal stability prove that the phosphor can be used as an efficient luminescent material in the field of full-spectrum LED devices. [ABSTRACT FROM AUTHOR]

Abstract We demonstrate the growth of ZnSe microspheres in large quantities by using a mixture of Zn and Se as precursors via direct current arc discharge method without the addition of any catalyst or template. The as-obtained samples were characterized by X-ray diffraction, Raman, energy-dispersive X-ray spectrometry, scanning and transmission electron microscopy, and ultraviolet-visible reflectance spectroscopy. The majority of the ZnSe microspheres which were composed of ZnSe nanoparticles exhibited perfectly spherical morphology and a distinct hollow structure with a relatively rough surface. The growth mechanism of ZnSe hollow microspheres has been discussed. Room-temperature excitation and emission spectra as well as the fluorescence lifetime of ZnSe hollow microspheres were measured and the results showed ZnSe hollow microspheres exhibit an intensive wide broad emission bands from 550 to 750 nm upon 470 nm excitation with fast decay time 1.09 ms and CIE chromaticity coordinates (0.65, 0.34), which was ascribed to characteristic structure defects (vacancies and interstitials) in ZnSe. Additionally, the temperature dependent emission behavior was measured and discussed. [ABSTRACT FROM AUTHOR]

Ba0.98-xLaxHf1-xScxSi3 O9:0.02Eu2+ (x = 0-0.02) is prepared by solid state reaction of stoichiometric amounts of BaCO3, La2O3, Sc2O3, HfO2, SiO2, and Eu2O3 (Al2O3 crucible, 1. [ABSTRACT FROM AUTHOR]

In the frame of exploring suitable yellow emission phosphors for blue light pumped high power warm LEDs, RbZnPO4:xDy3+ (x = 0-0.05) is investigated by powder XRD refinement and photoluminescence spectroscopy. [ABSTRACT FROM AUTHOR]

Cyan phosphors with high efficiency and excellent thermal stability are an important part for application in full spectrum illumination. Herein, a series of nitriding cyan emission phosphors Ca 2 (Y, Ce)Hf 2 (Al, Si) 3 (O, N) 12 with garnet structure are successfully synthesized. Their phase purity, crystal structure, morphology, elemental composition and valence state are analyzed in detail, and the results indicate that a small amount of Si 3 N 4 doping does not cause impurity phase. The phosphor has an efficient broadband cyan emission at 493 nm with full width at half maximum (FWHM) of about 95 nm under 411 nm excitation. Impressively, the luminous intensity of the nitriding phosphor is increased by 30%, the internal quantum efficiency is increased from 41.63% to 61.93%, and the thermal stability is improved from 75%@150 °C to 85%@150 °C, which is better than the commercial green phosphor (77%@150 °C). Finally, a full-visible-spectrum LED with low correlated color temperature (CCT = 5143 K) and high color rendering index (R a = 98.3) is fabricated by employing Ca 2 (Y, Ce)Hf 2 (Al, Si) 3 (O, N) 12 phosphors as cyan emitting component. The results indicate that the nitriding Ca 2 (Y, Ce)Hf 2 (Al, Si) 3 (O, N) 12 phosphors have potential to act as cyan emission phosphors for full-visible-spectrum LEDs. • An azotizing garnet phosphor with improved QE and thermal stability was synthesized. • Structure and luminescent property evolution before/after azotizing were discussed. • Site preference and the 5d→2F 5/2 and 2F 7/2 transitions of Ce3+ were accurately assigned. • The mechanism of the improved thermal stability after azotizing was discussed. • Full-visible-spectrum LEDs can be achieved with high R a and low CCT. [ABSTRACT FROM AUTHOR]

High power phosphor converted light emitting diodes (pc-LED) are thought to be the next generation technology for lighting and high-tech electronics applications. To achieve optimal luminous efficiency, maximal color gamut and stable color reproducibility, the discovery of high efficient phosphor materials with suitable excitation matching, narrow band emission and robust thermal stability is essential. Herein, we design and construct a new family of alkaline phosphate phosphors ANa 3 Mg 7 (PO 4) 6 :Eu2+ (ANMP:Eu2+, A = K, Rb and Cs) with rigid diamond-like chain structure. The results indicates that ANMP:Eu2+(A = K, Rb and Cs) phosphors exhibit ultra-small Stokes shift and efficient blue emission (λ max = 444–465 nm) with high internal quantum efficiency (IQE = 83.2%, 90.6% and 93.4% for A = K, Rb and Cs), narrow full width at half maximum (FWHM∼50 nm) and low thermal quenching (87.5%, 96.5% and 84.2%@140 °C for A = K, Rb and Cs), which demonstrate to have higher colorful purity, wider color gamut and better wavelength applicability for using in long-wavelength near ultraviolet (LWUV) LEDs, compared with the traditional commercially available blue phosphor BaMgAl 10 O 17 :Eu2+ (BAM:Eu2+). The Eu2+ site preferences and thermal quenching mechanism are studied in detail. Moreover, the in situ temperature dependent Raman spectra and density function theory (DFT) are employed to get better comprehensions of the relationship between crystal-electronic structures and luminescent properties from experiment and calculation, which will provide a good guidance for develop new phosphors with high QE and excellent thermal stability. Finally, utilizing the title phosphors, white LED lamps are fabricated with high color rendering index and an appropriate correlated color temperature. Therefore, all the results demonstrate that the blue-emitting phosphor ANMP:Eu2+ (A = Cs, K, Rb) has great potential for applications in high power LWUV pumped pc-LEDs. [ABSTRACT FROM AUTHOR]

RbZnPO 4 : x Sm 3+ (0.005 ≤ x ≤ 0.05) red phosphors were prepared for the first time. The phase purity, luminescence property and thermal stability were systematically determined by employing X-ray diffractometer, excitation and emission spectra and temperature dependent emission spectra. The site occupation of Sm 3+ in RbZnPO 4 was discussed based on the X-ray diffractometer analysis. The electronic structure property of RbZnPO 4 host was studied, which revealed that RbZnPO 4 possessed a direct band gap with band gap value of 3.815 eV. The photoluminescence emission spectra showed that RbZnPO 4 : x Sm 3+ (0.005 ≤ x ≤ 0.05) could absorb near-ultraviolet light around 404 nm and emit red emissions with dominated peaks at 601 and 647 nm, ascribed to the 4 G 5/2 to 6 H 7/2 and 6 H 9/2 transitions of Sm 3+ ions, respectively. The optimal doping concentration and the critical distance as well as the interaction mechanism of Sm 3+ in RbZnPO 4 were discussed. The interesting temperature sensitive thermal quenching behavior and the related mechanism were studied. [ABSTRACT FROM AUTHOR]

An efficient and ultra‐broadband red phosphor CsMg2P3O10: Mn2+ (CMPO: Mn2+) is first synthesized toward indoor plant growth LEDs. The phase purity, element composition, crystal, and local electronic structure are explored to discuss the structure and photoluminescence properties. Structure refinement and series X‐ray diffractometer (XRD) results show that CMPO: Mn2+ is well crystallized in an orthogonal crystal system. The diffuse reflection and excitation spectra show that CMPO: Mn2+ has strong absorption around near ultraviolet region, assigned to the [6A1 → 4E(4D), 4T2(4D), [4A1(4G), 4E(4G)], and 4T1(4G)] transitions of Mn2+, respectively. Upon 415 nm excitation, an efficient red emission centered at 647 nm with ultra‐broad full width at half‐maximum (FWHM ∼ 100 nm) and high quantum efficiency (IQE ∼ 44.3 %) is observed, and because of the ultra‐broad FWHM, the red emission is well accordant with the absorption spectra band of phytochrome PR and PFR. The optimal doping contents, lifetime as well as interaction mechanism of CMPO: Mn2+ are discussed in detail. Finally, the excellent thermal stability (84.5% @ 140°C) and related thermal quenching mechanism of CMPO: Mn2+ are discussed. The above results indicate that CMPO: Mn2+ phosphors have great potential for application in plant growth LEDs. [ABSTRACT FROM AUTHOR]

Ultra-broadband-emitting phosphors are crucial for achieving high-quality full-spectrum WLEDs. However, it is difficult to achieve ultra-broadband emission by doping a single luminescent center. In this work, we propose a strategy to achieve ultra-broadband orange-red emission through utilizing Eu2+ selective occupation in multi-cation sites whitlockite-type phosphate Sr 8 Mg 2 Na(PO 4) 7. The result indicates that Eu2+ can occupy Sr1Mg1, Sr2Mg2, and Sr3Mg3 sites, and generate an ultra-broadband emission ranging from 400 to 800 nm with dominant emission at 620 nm and a FWHM of 220 nm upon 385 nm excitation. Interestingly, a new emission shoulder at 430 nm is obtained, which is demonstrated to ascribed to Eu2+ occupying the Mg4Na1 site in a weak crystal field. As an ultra-broadband-emitting and red-light abundant phosphor, the full-spectrum WLEDs shows much higher color index than that of YAG: Ce3+. Moreover, an ultraviolet light pumped full-spectrum WLED with a high Ra (∼92) and low CCT (∼4275 K) is fabricated by mixing the Sr 8 Mg 2 Na(PO 4) 7 : Eu2+ and commercial phosphors BAM: Eu2+, Mn2+. In summary, this work deeply investigated the luminescence properties of Eu2+ in whitlockite-type phosphor Sr 8 Mg 2 Na(PO 4) 7 and is expected to guide the design of novel broadband-emitting phosphors with multi cationic sites for emerging full-spectrum WLED applications. • SMNPO was demonstrated to have multi-cation sites for luminescent center to occupy. • Ultra-broadband emission was achieved by doping Eu2+ ions into SMNPO. • The selective occupation of Eu2+ ions in multiple sites was analyzed in detail. • A full-spectrum WLED with high Ra (∼92) and low CCT (∼4275 K) was prepared. [ABSTRACT FROM AUTHOR]

The optical‐magnetic multifunctional materials are of great importance owing to their potential applications in intersect discipline fields. However, the multifunctional materials with satisfied optical and magnetic property are limited, and the modulation mechanism of their magneto‐optical property related to their structure feature is ambiguous. Here, a new multifunctional solid solution phosphors Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) are designed based on composition engineering and are successfully synthesized. The detailed structure feature including the structural evolution of the crystallographic parameters and local lattice environment as well as polyhedral distortion behavior are investigated through X‐ray diffraction Rietveld structure refinement for Ca18K3Sc1‐xSmx(PO4)14 in the full range (0 ≤ x ≤ 1). The photoluminescence spectra indicate that Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) can emit intense orange‐red emission (IQE~42.6%) under ultraviolet light excitation ascribed to the4G5/2 ‐6H7/2 transition of Sm3+ ions. The structure modulated luminescence behavior, for example, the tunable emission ratio of I648/I565, high quenching content, and electric multipole interaction mechanism are studied. The versatile phosphors can exhibit tunable orange‐red cathodoluminescence emission along with increasing the accelerating voltage. The electron transition mechanism of the photoluminescence and cathodoluminescence behavior is further discussed through a simple schematic diagram. Moreover, Ca18K3Sc1‐xSmx(PO4)14 (0 ≤ x ≤ 1) shows a ferromagnetic behavior with controllable magnetization and coercive field. Finally, the impact of Fe ions on the photoluminescence and magnetic property of Ca18K3Sc1‐yFey(PO4)14: 0.4Sm3+ (0 ≤ y ≤ 0.05 and y = 1) phosphors are investigated. The current research can provide some ideas and mechanism to design and investigate more novel magneto‐optical muntifunctional materials for versatile applications in intersect disciplines. [ABSTRACT FROM AUTHOR]

[Display omitted] • A heavy doping of Eu3+ (x = 50%) is realized in NaBa 10 Y 5-5 x W 4 O 30 : x Eu3+ without any impurity phase. • The phosphor obtains strong broad-band excitation around 315 nm due to the charge transfer transition from [WO 6 ]6- groups to Eu3+ ions. • The Eu3+ ions will enter highly symmetric lattice environment at the YO 6 site, and obtaining a strong orange-red emission peak (λ em = 596 nm) corresponding to the magnetic dipole 5D 0 →7F 1 transition. • The degree of local environmental distortion for Eu3+ ion is analyzed by the calculation of the asymmetry ratio (5D 0 →7F 2)/(5D 0 →7F 1). • The optimal sample NBYWO: 15%Eu3+ has a high color purity of 95.34%. • The NBYWO: 15%Eu3+ phosphor with commercial blue, green phosphor can obtain a wide color gamut of 76.21 % NTSC. In this work, we reported the synthesis and characteristic luminescence of an orange-red emitting phosphor NaBa 10 Y 5 W 4 O 30 : Eu3+ for ultra-violet white light emitting diodes. The phase compound, crystalline structure and morphology are analyzed. The results indicate that a heavy doping of Eu3+ (x = 50%) is realized in NaBa 10 Y 5-5 x W 4 O 30 : x Eu3+ without any impurity phase. Moreover, the optical band gap is analyzed by diffuse reflectance spectroscopy and further confirmed by density function theory (DFT). Meanwhile, the as-synthesized NaBa 10 Y 5 W 4 O 30 : Eu3+ phosphor can be efficiently pumped by strong broad-band excitation around 315 nm due to the charge transfer transition from [WO 6 ]6- groups to Eu3+. Owing to the highly symmetric lattice environment of Eu3+ in YO 6 sites, a strong orange-red emission at 596 nm with color purity of 95.34% is obtained, corresponding to the 5D 0 →7F 1 magnetic dipole transition of Eu3+ ions. The critical concentration is obtained to be x = 15%, and the quenching mechanism is discussed to be dipole–dipole interaction. Furthermore, the temperature dependent emission behavior are analyzed, and the thermal quenching mechanism are explained by the variable temperature decay curve and configuration coordination diagram. Finally, an orange-red light emitting diode lamp is fabricated based on NaBa 10 Y 5 W 4 O 30 : 15%Eu3+ phosphor and 315 nm semiconductor chip. In summary, the results indicate that NaBa 10 Y 5 W 4 O 30 : Eu3+ phosphor has the potential to be an orange-red phosphor for white light emitting diodes. [ABSTRACT FROM AUTHOR]

Abstract: Dy3+ doped NaSr2Nb5O15 series were firstly synthesized by solid-state reaction method. Crystal structure and characteristic luminescence properties are investigated in detail by X-ray diffraction refinement and photoluminescence spectra measurement. NaSr2Nb5O15:Dy3+ exhibits strong absorption in near ultraviolet–blue region and intense warm white emission with CIE chromaticity coordinates (0.396, 0.433) and low correlated color temperature (3970K) upon 388nm excitation. The warm white LED has also been fabricated by combining with GaN (365–370nm chip) and single NaSr2Nb5O15:Dy3+ phosphor. The results show that NaSr2Nb5O15:Dy3+ could be a promising phosphor for warm white LEDs. [Copyright &y& Elsevier]

A series of Sr 9 Mg 1.5 (PO 4) 7 :Tm3+, Dy3+ phosphors were prepared by conventional sintering method. Rietveld refinement, X-ray diffraction patterns, PL/PLE spectra, lifetimes and thermal quenching spectra were measured and investigated in detail. All the prepared phosphors crystalized to single phase and consisted of micronized particles. When excited by 358 nm, the emission hue of Sr 9 Mg 1.5 (PO 4) 7 :0.01 Tm3+, yDy3+ (0 ≤ y ≤ 0.20) turned from blue to white by modifying the Tm3+/Dy3+ ratio. The overlapped PL/PLE spectra and decreasing lifetimes of Sr 9 Mg 1.5 (PO 4) 7 :Tm3+, yDy3+ indicated the energy transfer from Tm3+ to Dy3+. Moreover, the resonance type energy transfer from sensitizer (Tm3+) to activator (Dy3+), CIE chromaticity and energy transfer efficiency were confirmed and discussed, too. The energy transfer mechanism was determined as a resonant type via dipole-dipole mechanism with 53.05% energy transfer efficiency when the doping content y = 0.02. The CIE chromaticity coordinates of Sr 9 Mg 1.5 (PO 4) 7 :0.01 Tm3+, 0.20Dy3+ was (0.3279, 0.3299) with 27.8% quantum efficiency. The sample also exhibited excellent thermal quenching performance with the remained 95% emission intensity at 150 °C compared with the original emission intensity at ambient temperature. The outstanding luminescence properties and excellent thermal stability suggested that Sr 9 Mg 1.5 (PO 4) 7 :0.01 Tm3+, 0.20Dy3+ phosphor had a potential application in WLEDs. [ABSTRACT FROM AUTHOR]

Tunable luminescence and efficient energy transfer investigation of a borosilicate phosphor KBSi 2 O 6 : Bi3+, Eu3+. [Display omitted] • Novel borosilicate phosphor KBSi 2 O 6 : Bi3+, Eu3+ are successfully synthesized. • Phase purity and tunable luminescence of KBSi 2 O 6 : Bi3+, Eu3+ are studied. • Effective energy transfer between Bi3+ and Eu3+ is demonstrated. • Hypersensitive thermal quenching is investigated with high S a and S r. Energy transfer between Bi3+ and Eu3+ has undergone substantial research but Bi3+ and Eu3+ co-doped luminescent materials with high energy transfer efficiency for temperature sensing are rarely investigated until now. Herein, Eu3+ and Bi3+ co-doped KBSi 2 O 6 phosphors were successfully synthesized by solid-state reaction method. The phase purity structure as well as the element distribution were carefully investigated through X-ray diffraction structural refinement and energy dispersive spectrometer analysis. The characteristic luminescence property and luminescence kinetics of KBSi 2 O 6 : Bi3+, Eu3+ were investigated. By the large spectra overlap between the emission spectrum of Bi3+ and excitation spectrum of Eu3+, the energy transfer from Bi3+ to Eu3+ can be inferred. The corresponding decrease of the emission intensity and decay time of Bi3+ in KBSi 2 O 6 : Bi3+, Eu3+ provided direct evidence for the effective energy transfer from Bi3+ to Eu3+. The interaction and energy transfer mechanism between Bi3+ and Eu3+ ions were also studied. By increasing the Eu3+ concentration in KBSi 2 O 6 : Bi3+, Eu3+, the color-tunable emission from blue to red can be realized. KBSi 2 O 6 : Bi3+, Eu3+ shows hypersensitive thermal quenching behavior and the maximum absolute sensitivity (S a) and relative sensitivity (S r) are determined to be 1.87 %K−1 and 2.895 %K−1, respectively. All of the above results imply that KBSi 2 O 6 : Bi3+, Eu3+ phosphor can be a color-tunable phosphor for optical temperature sensing. [ABSTRACT FROM AUTHOR]

A series of rare earth ions doped novel niobate phosphors SrBaNb 4 O 12 :Re3+ (Re= Eu, Dy, Sm and Pr) were successfully developed through solid state reaction. The phase composition and morphology were investigated through X-ray structure refinement, scanning electron microscopy and energy dispersive spectrometer. The layered crystal structure of SrBaNb 4 O 12 and the local lattice environment of Re3+ were discussed in detail. The electronic structure property and density of states were calculated based on density functional theory. To investigate the characteristic luminescence property, the excitation and emission spectra, fluorescence lifetimes and Commission Internationale de l'E′clairage (CIE) chromaticity index of SrBaNb 4 O 12 :Re3+ (Re= Eu, Dy, Sm and Pr) series phosphors were determined as well. [ABSTRACT FROM AUTHOR]

To research and develop potential phosphors for ultraviolet-based white light emitting diodes, a novel red emission phosphate phosphor Ca18Li3Bi1−xEux(PO4)14 was synthesized and investigated in the full range of 0 ≤x≤ 1. The phase purity and crystal structure of the solid solution phosphors were investigated in detail by employing X-ray diffractometer structure refinement, scanning electron microscopy and energy dispersive spectrometry. The crystal structure information was confirmed and the structure as well as the doping concentration dependent characteristic photoluminescence properties were discussed in detail. The results indicated that high Eu3+ doping content x could be realized in Ca18Li3Bi1−xEux(PO4)14 solid solutions even when x = 1. The luminescence performance revealed that Ca18Li3Bi1−xEux(PO4)14 phosphors could emit intense red emission under 394 nm excitation with excellent CIE chromaticity coordinates and high color purity. The concentration dependent emission decay behavior at room temperature and the temperature dependent decay behavior were studied to investigate the luminescent dynamics. The abnormal thermal quenching behavior was investigated via the temperature dependent emission. The related mechanism was discussed through thermoluminescence analysis, charge compensation contrast test and the cooling emission curve measurement, and the thermal activation energy was studied. The above results indicated that the Ca18Li3Bi1−xEux(PO4)14 could be a promising red-emitting phosphor for white light emitting diodes. [ABSTRACT FROM AUTHOR]

Abstract: Hydrothermal reaction at 150°C and pH = 10 for 24 hours crystallized (Gd,RE)2(OH)4SO4 layered hydroxide sulfate (monoclinic structure; RE = Pr, Tb), from which Gd2O2S:RE (hexagonal structure) green phosphor hexagons were derived via facile dehydration in flowing H2 at 1200°C. Rietveld refinement of the XRD patterns yielded cell dimensions that confirmed the direct crystallization of solid solution. Photoluminescence (PL) study at room temperature found absolute quantum yields of ~25.1% and 28.4%, CIE chromaticity coordinates of (0.145, 0.679) and (0.326, 0.566), and fluorescence lifetimes of ~2.36 μs and 1.21 ms for Pr3+ and Tb3+ under 300 and 275 nm UV excitations, respectively. Temperature‐dependent PL analysis (25‐200°C) indicated that both the Pr3+‐ and Tb3+‐doped phosphors have favorably good thermal stability and retained ~65% and 80% at 100°C and ~41% and 47% at 200°C of their initial emission intensities, respectively. The activation energy for the thermal quenching of PL was determined to be ~0.221 (Pr3+) and 0.314 eV (Tb3+). Cathodoluminescence (CL) found that both the phosphors exhibit increasingly higher emission intensity/brightness at a higher acceleration voltage (up to 7 kV) or beam current (up to 50 μA) and are stable under electron bombardment in the studied range. Raising beam current was suggested to be more effective to enhance CL. [ABSTRACT FROM AUTHOR]

Abstract A novel single-phase Eulytite-type orthophosphate Ba 7 Hf(PO 4) 6 :Dy3+ was prepared via sintering method. X-ray powder diffraction analysis confirmed the obtained samples were good single phase and no impure phase was found. The optical properties of Ba 7 Hf(PO 4) 6 :Dy3+ phosphors were characterized and the influence on the luminescent properties with various Dy3+ contents was studied clearly. Moreover, the photoluminescence spectra, decay times as well as the temperature quenching spectra of Ba 7 Hf(PO 4) 6 :Dy3+ phosphors were studied minutely. The experiment results illustrated the prepared Ba 7 Hf(PO 4) 6 :Dy3+ phosphor showed two photoluminescence bands centered at 485 nm and 578 nm which were attributed to 4F 9/2 → 6H 15/2 and 4F 9/2 → 6H 13/2 transitions of Dy3+ when pumped by UV. Meanwhile, an abnormal phenomenon was found that when the temperature increased, the emission intensity of Ba 7 Hf(PO 4) 6 :Dy3+ at 485 nm and 578 nm gradually decreased but the emission spectra at 451 nm assigned to 4I 15/2 → 6H 15/2 increased sharply with increasing temperature. Hence, temperature dependent 4I 15/2 → 6H 15/2 transition was analyzed in detail by X-ray powder diffraction, emission spectra and decay curves at different temperature, which was rarely discussed before. We found that the electrons preferentially select energy level transition of Dy3+ in Ba 7 Hf(PO 4) 6 through temperature control. All the results showed that Ba 7 Hf(PO 4) 6 :Dy3+ is a high-performance single-component phosphor. Highlights • An abnormal phenomenon was found that when the temperature increased, the emission intensity of Ba 7 Hf(PO 4) 6 :Dy3+ at 485 nm and 578 nm gradually decreased but the emission spectra at 451 nm assigned to 4I 15/2 → 6H 15/2 increased sharply. • Temperature dependent 4I 15/2 → 6H 15/2 transition was analyzed in detail by X-ray powder diffraction, emission spectra and decay curves at different temperature, which was rarely discussed before. [ABSTRACT FROM AUTHOR]

Pr 3+ activated niobate phosphors Ba 3- x ZrNb 4 O 15 : x Pr 3+ were firstly synthesized through high temperature solid-state method. The phase purity, crystal structure, morphology, luminescence property as well as thermal quenching behavior were carefully determined by using X-ray diffractometer, scanned electron microscope, photoluminescence and temperature dependent emission spectra, respectively. The luminescent property showed that Ba 3- x ZrNb 4 O 15 : x Pr 3+ (0.002 ≤  x  ≤ 0.03) had dominate excitation around 451 nm and could exhibit red emissions peaking at 608, 618 and 651 nm, attributed to the 1 D 2 - 3 H 4 , 3 P 0 - 3 H 6 and P 0 - 3 F 2 transitions of Pr 3+ ions. The different concentration quenching behaviors were found while the related mechanism was investigated. The room temperature decay times and the related fluorescence dynamics process of Pr 3+ ions in Ba 3 ZrNb 4 O 15 were investigated. In addition, the optimal doping contents, CIE chromaticity coordinates as well as the color purity were determined. At last, the temperature sensitive emission quenching and decay behavior were discussed and the activation energy was calculated based on Arrhenius equation. [ABSTRACT FROM AUTHOR]

Abstract: The thermal quenching properties and mechanisms of phosphors employed in white light emitting diodes (wLEDs) are critical for their commercial application. Here, we attempted to characterize the deep traps for capturing and releasing carriers to improve the thermal stability of the blue‐emitting CaAl2O4: Eu2+, Tm3+ phosphors. The enhanced thermal stability contributed to the introduction of traps has been demonstrated, and the mechanism of the transport process of carriers, has been explored in detail. In comparison with Eu2+ doped sample, the co‐doped Tm3+ samples bring more deep traps. The releasing of carriers in deep traps therefore sustains the luminescence with increasing temperature and compensates the thermal luminescence intensity loss. The results provide a theoretical basis and new field of view for exploring excellent thermal stability phosphors for wLEDs. [ABSTRACT FROM AUTHOR]

Sm 3+ activated niobate orange-red phosphors Ba 3 ZrNb 4 O 15 : Sm 3+ with temperature sensitive quenching behavior are firstly prepared with high temperature solid-state reaction method. The phase purity, characteristic luminescence property, decay times and thermal stability are systematically determined by employing X-ray diffractometer, photoluminescence spectra and temperature dependent emission spectra. The photoluminescence spectra shows that Ba 3 ZrNb 4 O 15 : xSm 3+ (0.005 ≤ x ≤ 0.04) can absorb near-ultraviolet light around 407 nm and emit orange-red emissions with dominated peak at 598 nm, ascribed to the 4 G 5/2 to 6 H 7/2 transitions of Sm 3+ ions. The optimal doping content as well as the Commission Internationale de L'Eclairage chromaticity coordinates of Ba 3 ZrNb 4 O 15 : Sm 3+ is studied. The energy transfer mechanism and the critical distance R c are investigated. The temperature dependent emission spectra reveal that Ba 3 ZrNb 4 O 15 : xSm 3+ exhibit temperature sensitive thermal quenching behavior and the thermal quenching mechanism is discussed. The results show that the orange-red phosphors Ba 3 ZrNb 4 O 15 : Sm 3+ have potential applications in some temperature sensitive devices. [ABSTRACT FROM AUTHOR]

Among the chemical doping elements, nitrogen atoms play a critical role in tuning the intrinsic properties or exploiting new phenomena of carbonaceous materials. Herein, we report a facile strategy to synthesize nitrogen-doped carbon dots (NCDs) using glutamic acid as the precursor via a one-step thermal conversion process. The as-produced NCDs exhibit bright blue photoluminescence (the quantum yield of ca. 23.2%), and the emission wavelength could be slightly tuned through changing the parameters of the synthesizing process. Interestingly, apart from their superior luminescence characters, unexpected cathodoluminescence (CL) and frequency upconverted emission properties were both observed in the NCDs. [ABSTRACT FROM AUTHOR]

Abstract: A new Ca2La8(GeO4)6O2 (CLGO) compound has been synthesized via solid-state reaction process for the first time. The crystal structure of CLGO was refined and determined by Maud Program. The photoluminescence spectra (PL), cathodoluminescence spectra (CL), and lifetimes as well as temperature dependence of photoluminescence of CLGO:RE3+ (RE3+=Eu3+, Tb3+, Dy3+, Sm3+, Tm3+) were investigated in detail. Under the excitation of ultraviolet, CLGO:RE3+ (RE3+=Eu3+, Tb3+, Dy3+, Sm3+, Tm3+) show red, green, yellow, orange, violet emission, respectively. [Copyright &y& Elsevier]

Europium-doped apatite Ca10(SiO4)3(SO4)3F2 (CSSF) has been successfully synthesized by solid state reaction. The crystal structure of CSSF:0.006Eu2+ is refined by the Maud refinement method. Optical properties of the prepared samples are found to depend on the rare-earth metal–oxygen distances and lattice iconicity. The excitation spectra of the CSSF:Eu2+ phosphors centered at 350 nm and covered the range from 250 to 450 nm. Under 350 nm excitation, the emission spectra of CSSF:Eu2+ phosphors show a blue (centered at 420 nm) and a green (centered at 525 nm) emission band, respectively. Meanwhile, the concentration quenching and energy transfer mechanism have been investigated via the configuration coordinate diagram. The key parameters, such as the temperature-dependent photoluminescence and CIE values of the CSSF:Eu2+ phosphor have also been studied. [ABSTRACT FROM AUTHOR]

Abstract: A series of Ag3PO4 and reduced graphite oxide sheets (RGOs) nanocomposites have been fabricated by a facile chemical precipitation approach in N,N-dimethylformamide (DMF) solvent without any hard/soft templates. The as-prepared Ag3PO4/RGOs composites were characterized by X-ray diffraction pattern (XRD), Fourier transform infrared spectra (FTIR), Raman spectroscopy, field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), and ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy (DRS). It is found that the nano-sized Ag3PO4 particles are deposited on the surfaces of RGOs. The Ag3PO4/RGOs nanocomposites exhibit enhanced photocatalytic activity for the photodegradation of organic methyl orange (MO) and methylene blue (MB) under visible light irradiation. The photocatalytic rate of Ag3PO4/2.1wt% RGOs nanocomposite is 3 and 2 times of that of pure Ag3PO4 nanoparticles for the degradation of MO and MB, respectively. Furthermore, the photocatalytic and structural stability of Ag3PO4 is greatly enhanced. It is suggested that RGOs can be used as protective coatings that partially inhibit the photocorrosion of Ag3PO4. Overall, this work could provide a new approach to the improvement not only in the photocatalytic activity but also the stability of photocorrosion catalysts. [Copyright &y& Elsevier]

Abstract: High quality and dispersible rare-earth oxides (RE2O3) nanocrystals have drawn great attention because of their potential applications in the optical, electrical and biological fields. Here, we demonstrated a simple approach for the production of gadolinium oxide (Gd2O3) nanoparticles onto the surface of reduced graphene oxide (RGO) sheets by the chemical and the subsequent thermal reduction reactions. The residual oxygen functionalities derived from the reduction of graphene oxide (GO) played an important role to complex Gd2O3 nanoparticles with RGO sheets. And the as-synthesized Gd2O3 nanoparticles are uniform and well-dispersed with their particle size in the range of 10–50nm. The approach would open up a new window for simple and effective synthesis of high quality RE2O3 in nano scale. [Copyright &y& Elsevier]

Abstract: A single-phased white-light-emitting phosphor Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+ (CMSC:Ce3+, Tb3+) is synthesized by a high temperature solid-state reaction method, and its photoluminescence properties are investigated. The obtained phosphor exhibits a strong excitation band between 250 and 410nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Energy transfer from Ce3+ to Tb3+ ions has been investigated and demonstrated to be a resonant type via a dipole–dipole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. Furthermore, the phosphors can generate light from yellow-green through white and eventually to blue by properly tuning the relative ratio of Ce3+ to Tb3+ ions grounded on the principle of energy transfer. The results show that this phosphor has potential applications as a single-phased phosphor for UV white-light LEDs. [Copyright &y& Elsevier]

Abstract: Eu2+, Mn2+ and Dy3+ co-doped long-lasting phosphors Sr3MgSi2O8 were prepared by a solid-state reaction under a reductive atmosphere. Fluorescence spectra demonstrated that the weak red emission resulting from the forbidden transition of Mn2+ could be enhanced by the energy transfer from Eu2+ to Mn2+. The energy transfer between Eu2+ and Mn2+ was systematically investigated. The phosphorescence spectra revealed that Eu2+ could persistently transfer its energy to Mn2+ after removing the excitation source. The duration of Mn2+ can prolong to more than 2h. The thermoluminescence spectra were used to characterize the ability of the trap to trapping the carriers. By the analysis of the ionization potentials, the roles of Mn2+ and Dy3+ in the afterglow process were discussed. A possible afterglow mechanism was presented and discussed. [Copyright &y& Elsevier]

Abstract: The photoluminescence properties of Si–N doped BaMgAl10O17:Eu2+, Mn2+ phosphors were studied. Photoluminescence spectrum, powder X-ray diffraction and decay curves were used. The electronic structure of un-doped BaMgAl10O17 was investigated by using the density functional theory. It reveals that an ideal hexagonal shape and particle size in 3–5μm are obtained by Si–N doping. Additionally, its photoluminescence and thermal stability are both improved. The energy transfer from Eu2+ to Mn2+ also enhanced by suitable Si–N doping. These are expected to be potentially applicable to industrial production of the phosphor in plasma display panels. [Copyright &y& Elsevier]

• Local structure modification is proposed to identify site preference of Eu2+. • Crystal structure and site occupation situation are renewedly defined. • Luminescent property, decay and thermal stability are investigated. • A full-color emission of SMP: Eu2+ is realized under UV light excitation. • A white LED with low CCT (~4663 K) and high Ra (~82) is fabricated. An understanding on the site preference of luminescence centers in phosphors serves as a starting point to illustrate the relationship between structure and luminescence. Till now, various methods such as theoretical calculation or modern testing techniques are employed to analyze their luminescent behavior and intrinsic mechanism. The present study proposes a local structure modification method to confirm the site occupation of Eu2+ ions in a whitlockite-type phosphor Sr 18 Mg 3 (PO 4) 14 : Eu2+. The result shows that Eu2+ ions can not only occupy Sr2+ sites but also substitute partial Mg2+ sites in Sr 18 Mg 3 (PO 4) 14. Owing to this, three emission bands centered at 420 (blue), 520 (green) and 620 nm (red) are simultaneously observed upon ultraviolet light excitation, resulting in a full color emission in Sr 18 Mg 3 (PO 4) 14 : Eu2+ phosphors. Meanwhile, the detailed structure information of Sr 18 Mg 3 (PO 4) 14 are renewedly evaluated and the optical spectroscopy property, decay curves and thermal quenching behavior as well as related mechanism of Sr 18 Mg 3 (PO 4) 14 : Eu2+ are studied in detail. Finally, an ultraviolet light pumped white LED is fabricated with suitable CCT of 4663 K and high R a of 82. The current analysis provides a deep insight into the origin of Eu2+ luminescence and its relationship with local lattice environment, which paves a new avenue to identify the site preference of luminescence centers. [ABSTRACT FROM AUTHOR]

• Novel CYLP:Dy3+ white phosphors were synthesized firstly. • Crystal structure, morphology and phase composition were examined. • Detailed excitation and emission spectra property of CYLP:Dy3+ was studied. • Interaction mechanism between Dy3+ and their decay time were investigated. • Thermal quenching behavior and related mechanism were discussed in detail. To explore novel single phase warm white light emitting phosphor, a series of phosphate phosphors Ca 18 Li 3 Y(PO 4) 14 :Dy3+ were prepared. The phase purity, crystal structure, morphology and element component were confirmed by XRD Rietveld structure refinement, SEM and EDS analysis. The luminescence process of Ca 18 Li 3 Y(PO 4) 14 :Dy3+ were systematically studied by photoluminescence spectroscopy and decay curves. The results indicated Ca 18 Li 3 Y(PO 4) 14 :Dy3+ phosphors had strong excitation from 300 nm to 420 nm. Under the excitation of 350 nm, warm white light emission was achieved with the CIE color coordinates of (0.399, 0.448) and low CCT of ~ 3992 K. The concentration quenching mechanism and quantum efficiency of Dy3+ in Ca 18 Li 3 Y(PO 4) 14 :Dy3+ were calculated and discussed in detail. The thermal quenching behavior revealed that Ca 18 Li 3 Y(PO 4) 14 :Dy3+ had excellent thermal stability with stable color rendition. The thermal activation energy was finally calculated. All the results indicated the potential application of Ca 18 Li 3 Y(PO 4) 14 :Dy3+ white light emission phosphor to be used in solid state lighting. Image, graphical abstract [ABSTRACT FROM AUTHOR]

• Novel CNMP: Dy3+, Tm3+ phosphors with adjustable emission was synthesized. • Detailed excitation and emission property of CNMP: Dy3+, Tm3+ was studied. • Room temperature and temperature dependent decay behavior were investigated. • The energy transfer efficiency and the energy transfer mechanism were investigated. • Thermal quenching behavior and related mechanism were investigated in detail. White light emission phosphors are widely researched for application in lighting and display fields. However, the poor thermal stability is a real problem for the known single-phased white phosphors, which limits their further application. In this paper, Ca 19 Na 2 Mg(PO 4) 14 : x Dy3+, y Tm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01) phosphors with adjustable emission and good thermal stability are synthesized. The X-ray diffraction and X-ray energy dispersive spectrometer measurement distinctly confirm the successful synthesis of CNMP: x Dy3+, y Tm3+ (CNMP, 0 ≤ x ≤ 0.06, y = 0, 0.01). The photoluminescence results reveal that CNMP: Dy3+ shows characteristic excitation peaks in the range of 350–450 nm, and mainly exhibits strong yellow emission around 575 nm ascribed to the 4F 9/2 -6H 13/2 transitions of Dy3+. To compensate the deficiency of blue light emission of CNMP: Dy3+, the trivalent Tm3+ ion is co-doped owing to its characteristic blue emission at 450 nm due to its 1D 2 -3F 4 transitions. Therefore, the emission of CNMP: Dy3+, Tm3+ can be tuned from blue light region with CIE coordinates of (0.1649, 0.0387) to white light region with CIE coordinates of (0.3001, 0.3003) and finally move to yellow light region with CIE coordinates of (0.3732, 0.4493) through adjusting the doping ratio of Dy3+/Tm3+. The energy transfer efficiency and the energy transfer mechanism from Tm3+ to Dy3+ are further investigated. Moreover, CNMP: Dy3+, Tm3+ exhibites a high thermal stability and the emission intensity still keeps 84% of the initial intensity of Dy3+ at 230 °C. These outstanding properties show that Ca 19 Na 2 Mg(PO 4) 14 : Dy3+, Tm3+ have great advantages and potentiality for applying in solid state lighting. [ABSTRACT FROM AUTHOR]

A series of novel red-emitting stannate phosphors Sr 2 SnO 4 : x Pr3+ (0 ≤ x ≤ 0.01) are developed through high temperature sintering reaction method. The crystal structure and phase purity are identified by X-ray diffraction and Rietveld structure refinement. The microstructure and element composition are characterized through scanning electron microscopy and energy dispersive spectrometer. To elaborate the characteristic luminescent property, the photoluminescence excitation and emission spectra, decay lifetimes as well as Commission Internationale de l'E'clairage color coordinates of Sr 2 SnO 4 : x Pr3+ (0 ≤ x ≤ 0.01) series phosphors are investigated. The results show that Sr 2 SnO 4 : x Pr3+ (0 ≤ x ≤ 0.01) phosphors have prominent excitation about 450 nm and can show red emissions peaking at 623, 652, 714 and 738 nm, respectively, ascribed to the 3P 0 –3H 6 , 3P 0 –3F 2 , 3P 0 –3F 3 and 3P 0 –3F 4 transitions of Pr3+ ions. The influences of the content of Pr3+ as well as charge compensation by co-doping with M+ (Li+, Na+ and K+) ions on the luminescent properties were discussed. The result reveals that co-doping Li+ ions can simultaneously increase the emission intensity and thermal stability. Furtherly, the mechanism of charge compensation and thermal quenching property are well studied through the temperature dependent decay curves and emission spectra. • Novel SSO: Pr3+, M+ red phosphors were synthesized firstly. • Detailed excitation and emission property of SSO: Pr3+, M+ was studied. • Room temperature and temperature dependent decay behavior were investigated. • Charge compensation ions were added and related mechanism were discussed. • Thermal quenching behavior and related mechanism were investigated in detail. [ABSTRACT FROM AUTHOR]

In this paper, we reported a novel far-red emitting phosphor Sr 9 Y 2 (WO 6) 4 : Mn4+ and alkaline earth metal Mg2+ ion co-doped phosphor Sr 9 Y 2 (WO 6) 4 : Mn4+, Mg2+. Systematical studies on its crystal structure and luminescence properties are carried out. X-ray powder diffraction confirmed that the pure phase Sr 9 Y 2 (WO 6) 4 : Mn4+ and Sr 9 Y 2 (WO 6) 4 : Mn4+, Mg2+ phosphors show a single phase. Upon 350 nm excitation, the phosphors could emit far-red emission in the range of 600–800 nm, peaking at 680 nm (14,706 cm−1) due to the 2E g →4A 2g transition, with broad spectra overlap with the absorption band of phytochrome P FR. The optimal doping concentration, concentration quenching mechanism, as well as the content and temperature dependent decay times of Sr 9 Y 2 (WO 6) 4 : Mn4+ phosphors are studied in detail. Impressively, Mg2+ dopant is found to strongly improve the luminescence of Mn4+ and the related mechanisms are deeply studied. Ultimately, a far-red light emitting diode lamp is fabricated by exciting a far red phosphor Sr 9 Y 2 (WO 6) 4 : 0.0025Mn4+, 0.01Mg2+ using a 365 nm n-UV illuminating LED chip. Our studies have shown that Sr 9 Y 2 (WO 6) 4 : Mn4+, Mg2+ phosphors have potential application in controlling or adjusting plant growth in plant-lighting. Image 1 • The charge compensation of Mg2+ was performed in the phosphor SYW: Mn4+. • We analyzed the crystal structure of SYW host at the first time. • The luminescence properties of SYW: Mn4+ and SYW: Mn4+, Mg2+ were systematically investigated. • The crystal field strength of SYW: Mn4+, Mg2+ with/without Mg2+ charge compensation were studied. • The SYW: Mn4+, Mg2+ phosphor was incorporated into a far-red LED lamp and its practicality was discussed. [ABSTRACT FROM AUTHOR]

Oxynitride Ba 3 Si 6 O 12 N 2 :Eu2+ phosphor can usually exhibit high color purity emission spectrum and outstanding thermal stability because of its rigid structure which can be widely used in WLEDs. With the aim of further optimizing the emission intensity, color purity and thermal stability, Al3+-doped Ba 3 Si 6 O 12 N 2 :Eu2+ green phosphors were successfully prepared by a high-temperature sintering method in the current work. The crystal structure was clearly investigated by the XRD patterns and Rietveld refinement. The expanding volume and elemental analysis proved that Si4+ ions can be efficiently substituted by Al3+ ions in the Ba 3 Si 6 O 12 N 2 :Eu2+ phosphor. With increasing doping of Al3+ ions, the full width at half maximum decreased from 66.88 to 65.12 nm with an optimal color purity of 65.95%, and the reason was clearly elucidated by the Gaussian fitting spectrum and decay times. Moreover, the emission intensity of Ba 3 Si 6 O 12 N 2 :0.1Eu2+, 0.03Al3+ was 120% of the intensity of the Al-free sample, and the internal quantum efficiency could reach 70%. The thermal stability was also remarkably enhanced as Al3+ substituted Si4+ in Ba 3 Si 6 O 12 N 2 :0.1Eu2+, and Ba 3 Si 6 O 12 N 2 :0.1Eu2+, 0.03Al3+ exhibited only 8% emission loss at 200 °C compared with that at ambient temperature. The outstanding thermal stability was clearly explained by the thermoluminescence spectra and configurational coordinate diagram. The results indicate that the introduction of Al3+ ions can be a versatile method to improve the optical properties of silicon oxynitride. • Ba 3 Si 6 O 12 N 2 : Eu2+, xAl3+ were successfully synthesized and investigated. • The emission intensity is 120% of the intensity of the Al-free sample. • Ba 3 Si 6 O 12 N 2 :0.1Eu2+, 0.03Al3+ phosphor exhibits only 8% emission loss at 200 °C. [ABSTRACT FROM AUTHOR]

By reduce the stoichiometry ratio of ZnO raw materials, we successfully redesign and tailor the luminescence properties of commercial plasma green Zn 2 SiO 4 :Mn2+ phosphors for using as white light emitting diodes phosphors due to the strong absorption intensity at 420 nm. When excited at 420 nm, the quantum efficiency of the best redesigned Zn 2 SiO 4 :Mn2+ green phosphor can reach 76.2% which is much higher than 1.26% of the original Zn 2 SiO 4 :Mn2+ phosphor. To make clear the mechanism of the strong absorption at 420 nm as well as the increasing quantum efficiency, several classical methods of investigation including Rietveld refinement, X-ray diffraction patterns, Raman spectra and PL/PLE spectra are measured in this study. When reducing ZnO raw materials, the increased randomly distributed oxygen vacancies will induce the deviation from the inversion center of symmetry lattice site and then increase the quantum efficiency. Moreover, the FWHM of the best redesigned Zn 2 SiO 4 :Mn2+ is narrower that of β-SiAlON:Eu2+ and commercial green phosphor LMS-520B which indicates the redesigned Zn 2 SiO 4 :Mn2+ is more suitable for using as backlights for LCD. The redesigned Zn 2 SiO 4 :Mn2+ phosphor can also exhibit 81.2% color purity and excellent thermal stability with only 30% emission intensity loss at 140 °C. In addition, with reduced ZnO, the long decay times of Zn 2 SiO 4 :Mn2+ phosphor caused by the restriction of parity-forbidden and spin-forbidden 4T 1 -6A 1 transition of Mn2+ can decrease from 4.168 ms to 3.268 ms. All the results suggest its great potential applications as backlights for LCD. • Zn 2 SiO 4 :Mn2+ phosphors are redesigned to exhibit strong absorption at 420 nm. • The redesigned Zn 2 SiO 4 :Mn2+ phosphor quantum efficiency can reach 76.2%. • The FWHM of redesigned Zn 2 SiO 4 :Mn2+ is narrower than that of β-SiAlON:Eu2+. • The redesigned Zn 2 SiO 4 :Mn2+ can be used as WLED phosphors. [ABSTRACT FROM AUTHOR]

A series of novel orange-red phosphors Sr 9 Mg 1.5 (PO 4) 7 : xSm3+ were synthesized by high temperature sintering method. Rietveld refinement, X-ray diffraction patterns, photoluminescence spectra, decay times and luminescence spectra showing thermal quenching were measured and investigated in detail. The mechanism of interaction for energy transfer, CIE chromaticity coordinates and color purity of the phosphors were studied and discussed, too. According to the Rietveld refinement, the coordination numbers of Sr2+ were reconfirmed based on the refined structure for the first time. Moreover, it was found that under near-ultraviolet excitation, Sr 9 Mg 1.5 (PO 4) 7 : xSm3+ exhibited an intense orange-red emission centering at 598 nm and 650 nm which can be assigned to 4G 5/2 to 6H 7/2 and 6H 9/2 energy level transitions of Sm3+, respectively. The CIE chromaticity coordinates of Sr 9 Mg 1.5 (PO 4) 7 : 0.2Sm3+ was (0.6066, 0.3923) with outstanding color purity of 98.8%. The sample also exhibited good thermal quenching properties with the remained 70% emission intensity at 150 °C compared with that at ambient temperature. Furthermore, in order to further improve the luminescent intensity and the thermal stability, Li+, Na+ and K+ were incorporated into Sr 9 Mg 1.5 (PO 4) 7 :0.2Sm3+ as the compensator charges. Among all the samples with compensator charges, Sr 9 Mg 1.5 (PO 4) 7 :0.2Sm3+, 0.2Na+ presented the highest emission intensity and best temperature quenching properties because of the similar radius of Na+ and Sr2+. The improved and linear thermal stability and strong luminescence intensity suggested that Sr 9 Mg 1.5 (PO 4) 7 :0.2Sm3+, 0.2Na+ has a potential use in solid-state lighting. • Sr 9 Mg 1.5 (PO 4) 7 : Sm3+ phosphor was successfully synthesized and investigated. • We reconsider the Sr 9 Mg 1.5 (PO 4) 7 structure and coordination numbers of Sr2+ ions. • Sr 9 Mg 1.5 (PO 4) 7 : Sm3+ phosphor can exhibit small thermal quenching performance. [ABSTRACT FROM AUTHOR]

Yb3+/Er3+, Yb3+/Tm3+, or Yb3+/Er3+/Tm3+ (25, 1, and 0.5 mol%, resp.) co-doped Ca9Y(PO4)7 are prepared by hydrothermal reaction of a stoichiometric solution of CaCO3, Y2O3, and lanthanide oxides in HNO3 to which (NH4)2HPO4 is added at a controlled pH of 8 (autoclave, 200 °C, 10 h) followed by annealing in air (850 °C, 2 h). [ABSTRACT FROM AUTHOR]