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The solid-state reaction method was used to develop a series of Na 2 Ca 1-x-y Ce x Mn y P 2 O 7 phosphors in an H 2 –N 2 environment. The crystal structure of the pyrophosphate host, valence state of dopants (Ce, Mn), emission behavior of dopants, energy transfer mechanism, and thermal quenching behavior were thoroughly examined. Doping with Ce3+ and Mn2+ ions enhanced the photoluminescence characteristics of Na 2 Ca 1-x-y Ce x Mn y P 2 O 7 while having negligible effect on the host's phase purity. Under 365 nm UV light irradiation, the addition of Ce3+ ion in the Na 2 CaP 2 O 7 host revealed an asymmetric band with the typical blue emission around 415 nm and a shoulder around 455 nm. To obtain white light, Mn2+ ion was supplementarily substituted to the present system. When the Mn2+ ions concentration was elevated in the Na 2 CaP 2 O 7 host, the emission intensity of 560 nm peak corresponding to Mn2+ transition enhanced significantly at the cost of Ce3+ emission of 415 nm. The systematic decrease of Ce3+ emission intensity and corresponding increase in the Mn2+ intensity with the increase in Mn2+ concentration indicated the possibility of effective energy transfer from Ce3+ to Mn2+ ions. The obtained results indicated that energy transfer from the Ce3+ to Mn2+ ions governed by dipole-quadrupole interaction. Because of the efficient energy transfer, the blue emission from Ce3+ and the orange red emission of Mn2+ provide white light from a single host along with high value of activation energy and low thermal quenching behaviour make the present phosphors to be suitable for high-power LEDs. [ABSTRACT FROM AUTHOR]

Currently, developing thermostable and color tunable phosphor via energy transfer strategy is a significant research topic in solid-state lighting field. Herein, the sensitizer Dy3+ and activator Sm3+ are solidly dissolved into the Ba 2 Y 2 Ge 4 O 13 (BYGO) matrix to prepare color-tunable germanate phosphors BYGO:Dy3+,Sm3+. Under 365 nm excitation, the energy transfer-induced tunable emission of Dy3+/Sm3+ co-doped phosphors are investigated. The energy transfer mechanism is ascribed to the quadrupole-quadrupole interaction. The thermal quenching investigation manifests that the BYGO:Dy3+,Sm3+ phosphor has excellent thermostability (the emission intensity at 423 K reduces only 6.9 %) and resistance to chromaticity shifting (the chromaticity shifting parameter at 473 K is as low as 3.94 × 10−3). Meanwhile, the ∼365 nm InGaN chip-excited w-LED device is fabricated with commercial phosphor BaSi 2 O 2 N 2 :Eu2+ and the title material, showing satisfactory electroluminescence performance. This work reveals that the title phosphor is a suitable candidate for solid-state lighting. • Due to the Dy3+→Sm3+ ET, the tunable emission of the BYGO:Dy3+,Sm3+ phosphor is realized. • The BYGO:Dy3+,Sm3+ phosphor shows excellent luminescent thermostability and chromaticity shifting resistance. • The fabricated w-LED device outputs satisfactory white light (0.3399, 0.3680). [ABSTRACT FROM AUTHOR]

A series of europium-ion doped CaLa 4 Si 3 O 13 phosphors were synthesized by using a conventional high-temperature solid-state method. X-ray powder diffraction patterns and photoluminescence spectra were utilized to characterize the as-prepared phosphors. The phosphors show tunable luminescence owing to the existence of Eu2+ and Eu3+ emission. A typical emission maximum of Eu2+ is about 460 nm, and Eu3+ shows a predominant 5D 0 -7F 2 transition emission. The emission of Eu2+ shifts toward the long wavelength side with increasing doping concentration. The site occupancy of Eu2+ and Eu3+ is analyzed according to their luminescence behaviors. The Eu3+ ion at the Ca2+ site can be partially reduced to Eu2+, but at the La3+ site cannot be reduced. The controllable reducing of Eu3+ is explained according to the crystal structure of the host. Utilizing site selection to control the reducing of Eu3+ is considered as an alternative strategy to design novel Eu3+ and Eu2+ codoped inorganic phosphor. [ABSTRACT FROM AUTHOR]

Sm3+ and Ce3+ singly doped and Sm3+ and Ce3+ co-doped Sr3B2O6 phosphors are prepared via a high-temperature solid-state reaction method. The crystal structure and phase purity are characterized by X-ray diffraction (XRD) analyses. The Sm3+-doped sample displays an emission in the orange-red region, with the strongest emission line at about 648 nm and possessing a good luminescence thermal stability between 78 and 500 K. With the increase in the Sm3+ content, the concentration quenching is observed due to the cross-relaxation (CR) processes among the Sm3+ ions. Upon 340 nm excitation, the Ce3+-doped phosphor presents a broad emission band in the blue region with a maximum at about 420 nm, which overlaps well with the 6H5/2 → 6P3/2 excitation line of Sm3+ and implies the possible energy transfer from Ce3+ to Sm3+. The spectral and decay measurements of the Ce3+ and Sm3+ co-doped samples are conducted and the Inokuti–Hirayama (I-H) model is adopted to analyze the luminescence decay dynamics of the donor Ce3+. Owing to the evident sensitization of the Sm3+ by the Ce3+ ions, the co-doped samples exhibit color variation under different wavelength excitations, endowing them with potential applications in optical anti-counterfeiting. [ABSTRACT FROM AUTHOR]

By balancing the luminescent modes of KLSO: yTb3+/xBi3+ phosphors in the fields of thermal response, time resolution and luminescent color, a novel differential display strategy is designed to achieve an anti-counterfeiting application with flexible transition properties. [Display omitted] Optical anti-counterfeiting and encryption have become a hotspot in information security. However, the advanced optical anti-counterfeiting technology still suffers from low security by single-luminescent mode. Herein, we present a novel multi-mode anti-counterfeiting strategy based on K 3 LuSi 2 O 7 : Tb3+/Bi3+ (KLSO: Tb3+/Bi3+) phosphors for the first time. KLSO not only provides various lattice sites for Bi3+ ions occupying to achieve tunable luminescence but can also be non-equivalently substituted by Tb3+ ions to produce persistent or thermo-luminescence. Furthermore, in the pattern "8888" constructed by the mixture of polyacrylic acid (PAA) with KLSO: Tb3+/Bi3+ phosphors, we selectively trigger the three luminescent modes of Bi3+ and Tb3+ ions to realize the design of differential display in the fields of thermal response, time resolution, and luminescence color for optical anti-counterfeiting. The differentiated display can only be presented under specific multi-stimuli response, which further improves the security of information. Our work provides a new insight for designing advanced materials and can be expected to inspire future studies to explore optical anti-counterfeiting technology. [ABSTRACT FROM AUTHOR]

Bi3+/Tb3+/Mn2+-doped Sr 3 Y 2 Ge 3 O 12 phosphors were synthesized, and their luminescence performance was investigated. Upon excitation with UV/NUV, the Sr 3 Y 2 Ge 3 O 12 :Bi3+, Sr 3 Y 2 Ge 3 O 12 :Tb3+ and Sr 3 Y 2 Ge 3 O 12 :Mn2+ phosphors showed prominent cyan, green and red emissions, respectively. Energy transfer processes occur in Bi3+/Tb3+, Bi3+/Mn2+ and Bi3+/Tb3+/Mn2+-codoped Sr 3 Y 2 Ge 3 O 12 phosphors, which leads to tunable luminescence. The calculated CIE coordinates on the basis of the emission spectra indicate that the tunability of the luminescence for the Bi3+/Tb3+-codoped Sr 3 Y 2 Ge 3 O 12 phosphors is not conspicuous. Their light is mainly located in the cyan light region. However, for the Bi3+/Mn2+-codoped Sr 3 Y 2 Ge 3 O 12 phosphors with a fixed Bi3+ concentration of 2 mol% and changing Mn2+ concentration, the emission shifts from the blue light region to the near white light region. After the doping of the Tb3+ ions in the Sr 3 Y 2 Ge 3 O 12 :2%Bi3+/5%Mn2+ phosphors, white light is generated. The CCTs of the light of the Bi3+/Tb3+/Mn2+-codoped Sr 3 Y 2 Ge 3 O 12 phosphors decreased continuously with increasing Tb3+ concentration. Warm white light is generated by the Sr 3 Y 2 Ge 3 O 12 :2%Bi3+/5%Tb3+/5%Mn2+ phosphor. [ABSTRACT FROM AUTHOR]

Single-phase white phosphors have broad application prospects in phosphor-converted white light emitting diodes. Herein, a series of novel single-phase Tm3+/Dy3+ doped Na 5 Lu(WO 4) 4 phosphors were prepared. The detailed investigation of its luminescence behavior showed that Na 5 Lu(WO 4) 4 : x Tm3+, y Dy3+ achieved tunable luminescence through the energy transfer process of Tm3+→Dy3+ at 365 nm excitation. According to the concentration-dependent emission spectra results, the electric dipole-dipole interaction was dominant to be responsible for all the energy transfer processes within the singly- and doubly-doped scenarios. Temperature dependent photoluminescence spectra suggested the excellent thermal stability of Na 5 Lu(WO 4) 4 :9%Tm3+,5%Dy3+ phosphor, of which the luminescence intensity at 421 K and 471 K was only 13.4% and 18.63% lower than that at room temperature, respectively. Finally, Na 5 Lu(WO 4) 4 :9%Tm3+,5%Dy3+ phosphor was packaged with a 365 nm near-ultraviolet LED chip, which exhibited bright blue and yellow emission bands at various bias currents. This work suggests that the developed single-phase Na 5 Lu(WO 4) 4 :Tm3+,Dy3+ phosphors have potential application prospects in the daily lighting field. • Warm white emission color (0.33119,0.33132) is achieved by adjusting Tm3+/Dy3+ ratios in Na 5 Lu(WO 4) 4. • Energy transfer mechanisms between Ln3+ of phosphors are attributed to the electric dipole-dipole interaction. • High thermal stability up to 86% and 81% is observed at 421 K and 471 K, respectively. [ABSTRACT FROM AUTHOR]

Ce3+- or/and Dy3+-doped Mg2Al4Si5O18 phosphors have been fabricated via a sintering process at 1400°C for 5 h and their crystallinity and luminescence characteristics investigated. x-Ray powder diffraction analysis demonstrated that Ce3+/Dy3+ ions entered the Mg2Al4Si5O18 host and formed a solid solution. When excited at 345 nm, Ce3+-doped Mg2Al4Si5O18 phosphor emitted light in the blue region while Dy3+-doped Mg2Al4Si5O18 phosphor emitted light in the yellow region. When excited at 345 nm, emission bands located in both the blue and yellow regions were observed for the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor. Because of Ce3+ → Dy3+ energy transfers, the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor showed tunable luminescence, changing from the blue to yellow–green region through the white region with increasing Dy3+ concentration in the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphor. The decay characteristics of the Ce3+ emission in the Ce3+/Dy3+-codoped Mg2Al4Si5O18 phosphors were also investigated. With increasing Dy3+ concentration, the lifetime of the Ce3+ emission decreased continuously, further confirming the occurrence of Ce3+ → Dy3+ energy transfer. [ABSTRACT FROM AUTHOR]

LaScO3:xBi3+,yTb3+,zEu3+ (x = 0 − 0.04, y = 0 − 0.05, z = 0 − 0.05) phosphors were prepared via high‐temperature solid‐state reaction. Phase identification and crystal structures of the LaScO3:xBi3+,yTb3+,zEu3+ phosphors were investigated by X‐ray diffraction (XRD). Crystal structure of phosphors was analyzed by Rietveld refinement and transmission electron microscopy (TEM). The luminescent performance of these trichromatic phosphors is investigated by diffuse reflection spectra and photoluminescence. The phenomenon of energy transfer from Bi3+ and Tb3+ to Eu3+ in LaScO3:xBi3+,yTb3+,zEu3+ phosphors was investigated. By changing the ratio of x, y, and z, trichromatic can be obtained in the LaScO3 host, including red, green, and blue emission with peak centered at 613, 544, and 428 nm, respectively. Therefore, two kinds of white light‐emitting phosphors were obtained, LaScO3:0.02Bi3+,0.05Tb3+,zEu3+ and LaScO3:0.02Bi3+,0.03Eu3+,yTb3+. The energy transfer was characterized by decay times of the LaScO3:xBi3+, yTb3+, zEu3+ phosphors. Moreover absolute internal QY and CIE chromatic coordinates are shown. The potential optical thermometry application of LaScO3:Bi3+,Eu3+ was based on the temperature sensitivity of the fluorescence intensity ratio (FIR). The maximum Sa and Sr are 0.118 K−1 (at 473.15 K) and 0.795% K−1 (at 448.15 K), respectively. Hence, the LaScO3:Bi3+,Eu3+ phosphor is a good material for optical temperature sensing. [ABSTRACT FROM AUTHOR]

Double perovskite materials have become the first choice of luminescent matrix materials in recent years due to their advantages of more flexible, easy doping and stable performance. A series of Y 2- x - y Tm x Sm y MgTiO 6 (0 ≤ x ≤ 0.5, 0 ≤ y ≤ 0.2) phosphors were prepared by high temperature solid-state method using different concentrations of Tm3+ and Sm3+ as dopants. The X-ray diffraction spectrum (XRD), photoluminescence spectrum (PL), fluorescence lifetime curve and X-ray excitation luminescence spectrum (XEL) of the phosphors were measured. The measurement results show that the dopants Tm3+ and Sm3+ enter the host lattice and replace part of the position of Y3+. The Tm3+ -doped sample emits strong blue light (458 nm) under 360 nm excitation, and the Sm3+ -doped sample has obvious emission peaks at 568 nm, 605 nm, 652 nm and 715 nm under 409 nm excitation. The energy transfer behavior of Tm3+→Sm3+ exists in the double doped samples. The energy transfer mechanism is consistent with the mechanism of concentration quenching in the system. Tunable luminescence can be realized by changing the doping concentration and excitation wavelength, which has great application value in the field of LED lighting. The energy transfer process and energy transfer efficiency in the system can be determined from the fluorescence lifetime curve of the sample. The phosphor can be effectively excited by X-ray, and the sample has good heat resistance and radiation resistance, which can be applied to the field of X-ray imaging. In addition, the thermal excitation effects of temperature on the 4G 5/2 → 6H 5/2 (568 nm) and 4G 5/2 → 6H 7/2 (605 nm) characteristic transitions of Sm3+ are different. Optical temperature measurement can be realized by using the fluorescence intensity ratio of I 568 nm /I 605 nm. Good temperature measurement performance and temperature measurement range have obvious advantages in the field of non-contact optical temperature measurement. • Y 2- x - y Tm x Sm y MgTiO 6 phosphors were successfully prepared and their doping details and cell parameters were obtained. • The energy transfer and tunable luminescence of Y 2- x - y Tm x Sm y MgTiO 6 phosphors were confirmed. • Y 2- x - y Tm x Sm y MgTiO 6 phosphor has good thermal stability and radiation resistance. • Y 2- x - y Tm x Sm y MgTiO 6 phosphor can be used for optical temperature sensing with X-ray. [ABSTRACT FROM AUTHOR]

High-performing lanthanide (Ln3+)-based luminescence thermometry is gaining widespread attention for its remote temperature reading, broad temperature range, high sensitivity, resolution, and stability in various applications. However, facile strategies for constructing multi-mode luminescence thermometry based on a simple material system are still challenging. Herein, we propose a dual-mode single-band ratiometric (SBR) luminescence thermometry based on the tunable Eu3+ luminescence in La 2 (WO 4) 3 (LaWO). Eu3+-doped La 2 (WO 4) 3 (LaWO:Eu) phosphor was synthesized by the high-temperature solid-state method. The rigid lattice of LaWO allows high content of Eu3+ doping without concentration quenching of luminescence, which endows high fluorescence intensity. In addition, in-situ and dynamic regulations of thermal-responsive luminescent properties of Eu3+ are systematically investigated, which enables the construction of SBR luminescence thermometry. At temperatures from 300 to 500 K, the maximum absolute and relative sensitivities reach 0.032 K-1 and 0.85% K−1, respectively. The high sensitivity and stability indicate that our results provide a facile and effective strategy for developing multi-mode luminescence thermometry and hold potential applications in various fields. [Display omitted] • Luminescence thermometry based on La 2 (WO 4) 3 :Eu3+ is reported for the first time. • Dual-mode SBR luminescence thermometry is realized simultaneously. • Tunable luminescence of Eu3+ enable high-performing luminescence thermometry based on a simple material system. [ABSTRACT FROM AUTHOR]

A series of Ce3+/Tb3+/Eu3+ singly doped, codoped and tri-doped Ca 2 MgSi 2 O 7 phosphors were prepared by a solid state reaction. The XRD patterns suggest that the rare earth ions have doped into Ca 2 MgSi 2 O 7 hosts entirely and formed phosphors with a single phase. To investigate the energy transfer of Ce3+ → Tb3+ → Eu3+, the excitation and emission spectra of the prepared Ce3+/Tb3+/Eu3+ singly doped, codoped and tri-doped Ca 2 MgSi 2 O 7 phosphors were measured. The excitation and emission spectra of Ce3+/Tb3+/Eu3+ singly doped Ca 2 MgSi 2 O 7 phosphors show that the Ce3+ emission band overlaps with the excitation bands of Tb3+ and Eu3+, and the emission bands of Tb3+ overlap with the excitation bands of Eu3+. The emission spectra of Ce3+/Eu3+, Ce3+/Tb3+ and Tb3+/Eu3+ codoped phosphors demonstrate that the Ce3+ → Eu3+ energy transfer is forbade but the Ce3+ → Tb3+ and Tb3+ → Eu3+ energy transfers occur. The emission spectra of Ce3+/Tb3+/Eu3+ tri-doped Ca 2 MgSi 2 O 7 phosphors demonstrate the energy transfer from Ce3+ to Eu3+ could be obtained through the Tb3+ chain. [ABSTRACT FROM AUTHOR]

Abstract Sc 2 W 3 O 12 is an important host matrix for rare-earth doped luminescence. However, the conventional method to prepare the material is solid-state reaction, which results into coarse and irregular morphologies. In this work, Eu3+ doped Sc 2 W 3 O 12 phosphors with high crystallinity and pure phase were successfully synthesized via one-step hydrothermal method. It was found that the crystalline phase changed from Sc 2 W 3 O 12 phase to Na 4 Sc 2 (WO 4) 5 phase when the molar ratio between Sc(NO 3) 3 and Na 2 WO 4 decreased. The temperature-dependent X-ray diffraction analysis was performed to prove the negative thermal expansion property of Sc 2 W 3 O 12. A systematic study on the effect of reaction time, temperature and Eu3+ doping concentration was explored. It was also found that the as-prepared samples displayed tunable emission colors, ranging from blueish white to orange red. Particularly, the white light emission with the chromaticity coordinate of (0.3395, 0.3289) can be realized in Sc 2 W 3 O 12 : 5% Eu3+. What's more, the photoluminescence properties of the samples were investigated under different ambient temperatures between 97 and 280 K. The result clearly showed energy transfer between Eu3+ and WO 4 2−. The above results suggested that Sc 2 W 3 O 12 :Eu3+ can be excellent candidate for solid-state lasing, panel display and WLEDs. [ABSTRACT FROM AUTHOR]

Abstract This paper demonstrates that a highly thermal stable and tunable-luminescence phosphors Y 3 Al 2 Ga 3 O 12 : Tb3+, Eu3+ with efficient energy transfer, which is prepared by the high-temperature solid-state reaction. First-principles method is performed to analyze the electronic structures, band structure, density of states and formation energy of Y 3 Al 2 Ga 3 O 12 : Tb3+, Eu3+. For high luminescence output, Y 3- x Al 2 Ga 3 O 12 : x Tb3+ and Y 3- y Al 2 Ga 3 O 12 : y Eu3+ with high concentration quenching (x = 0.5 and y = 0.7) are achieved. The effect of energy transfer from Tb3+ to Eu3+on emission color tuning and luminescence thermal stability is studied. The energy transfer efficiency from Tb3+ to Eu3+ reaches as high as 74.2% and emission color can be tuned from green, yellow and red by adjusting the ratio of Tb3+/Eu3+. What's more, Y 3 Al 2 Ga 3 O 12 : Tb3+, Eu3+ phosphor exhibits a good thermal stability, of which emission intensity still keeps 60% at 150 °C. Highlights • The color-tunable emission is obtained by adjusting the ratio of Eu3+ and Tb3+. • The energy transfer mechanism of Y 3 Al 2 Ga 3 O 12 : Tb3+, Eu3+ is discussed in detail. • Y 3 Al 2 Ga 3 O 12 : Tb3+, Eu3+ phosphor show high thermal stabilities. [ABSTRACT FROM AUTHOR]

Abstract A series of Ca 5 (BO 3) 3 F: Tb3+/Eu3+ phosphors have been prepared via solid-state reaction. Phase purity and crystal structure of as-prepared samples are confirmed by X-ray diffraction measurements. The emission intensity of Ca 5 (BO 3) 3 F: Tb3+ with Li+, Na+, K+ as charge compensators are remarkably enhanced, and the sample in presence of Na+ exhibits the strongest emission intensity. The emission spectra and fluorescence decays confirm the presence of efficient energy transfers from Tb3+ to Eu3+ in Ca 5 (BO 3) 3 F: Tb3+/Eu3+ phosphors. The energy transfer mechanism between Tb3+ and Eu3+ has been proven to be resonant type via the electric dipole-dipole interaction. The thermal quenching temperature T 50 obtained from the temperature-dependent emission spectra is 478 K, demonstrating a high thermal stability of the as-obtained Ca 5 (BO 3) 3 F: Tb3+/Eu3+ phosphors. Moreover, by increasing the molar ratio of Eu3+ to Tb3+, the emission colors of Ca 5 (BO 3) 3 F: Tb3+/Eu3+ phosphors can be tuned from green to orange, and then to red. These results demonstrate that the as-obtained Ca 5 (BO 3) 3 F: Tb3+/Eu3+ phosphors may have potential applications in solid-state lighting fields. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Abstract In this work, Pr3+ and Tb3+ coactivated Na 5 Gd(WO 4) 4 (NGW) phosphors have been synthesized by high-temperature solid-state reactions and the scheelite crystal structure was determined for the first time. A color-tunable emission in NGW: Pr3+, Tb3+ phosphors can be realized by the modulation of excitation wavelengths, namely, the fluorescence intensity ratio of Pr3+ to Tb3+ in this material could be changed by different excitation. With increasing temperature, the luminescence of NGW: Pr3+, Tb3+ phosphor decreases almost linearly with the CIE coordinate variation from (0.306, 0.392) to ((0.375, 0.465) and result in the color of the photoluminescence variation from the blue-green to yellow. These results demonstrated that the investigated phosphors are attractive for application in display lighting and optical temperature sensing. Highlights • A novel phosphor Na 5 Gd(WO 4) 4 : Pr3+, Tb3+ has been synthesized. • The scheelite crystal structure of Na 5 Gd(WO 4) 4 was determined for the first time. • The color-tunable emission properties of Na 5 Gd(WO 4) 4 : Pr3+, Tb3+ have been realized. • Na 5 Gd(WO 4) 4 : Pr3+, Tb3+ phosphor shows high thermostability. [ABSTRACT FROM AUTHOR]

Abstract The Sr (1- x) Al 2 O 4 : x Eu3+ (0 ≤ x ≤ 5.0%) phosphors were synthesized by solid state reaction method. They crystallized in monoclinic structure and well consistent with that of JCPDS No.34–0379. Thermal and compositional analysis was described in detail. The photoluminescence excitation spectra were recorded monitoring the emission at 612 nm corresponding to the Eu3+: 5D 0 → 7F 2 transition. The photoluminescence excitation spectrum of undoped SrAl 2 O 4 consists of a broad band with maximum at 278 nm, while the Eu3+ -doped phosphors contain similar broad band of lower intensity and Eu3+ characteristic bands. The photoluminescence properties were analyzed by exciting the studied phosphors at 278 nm (within the host) and at 395 nm (within the Eu3+) wavelengths. The SrAl 2 O 4 :Eu3+ phosphors show bluish-pink luminescence at 278 nm excitation and concentration dependent luminescence at 395 nm excitation. The local site symmetry of the host material around the Eu3+ ions was studied by calculating the Judd-Ofelt intensity parameters using the Eu3+: 5D 0 → 7F J (J = 1, 2 and 4) transitions. The experimental results show that the SrAl 2 O 4 : Eu3+ phosphors are potential for solid state lighting and display devices. Highlights • SrAl 2 O 4 :Eu3+ phosphors were crystallized into monoclinic structure. • SrAl 2 O 4 :Eu3+ phosphors exhibit bluish-pink luminescence at 278 nm excitation. • SrAl 2 O 4 :Eu3+ phosphors exhibit tunable luminescence at 395 nm excitation. • SrAl 2 O 4 : Eu3+ phosphors are potential for solid state lighting and display devices. [ABSTRACT FROM AUTHOR]

Abstract A batch of Bi3+/Eu3+ single and co-doped BaGd 2 O 4 phosphors were elaborated by traditional high temperature solid-state method. Their structural and photoluminescent properties were methodically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), excitation spectra, emission spectra, decay curves as well as temperature dependent emission spectra. Under ultraviolet (UV) excitation, via a high-efficiency energy transfer process, the prepared Bi3+/Eu3+ co-doped BaGd 2 O 4 phosphors reveal both blue wide emission from Bi3+ ions and characteristic red sharp emission from Eu3+ ions. The energy transfer mechanism, energy transfer efficiency and luminescence chromaticity coordinates were procured. Our results indicate that BaGd 2 O 4 :Bi3+, y Eu3+ phosphors may act as promising candidate to boost the photosynthesis of plant. [ABSTRACT FROM AUTHOR]

A new anionic coordination polymer (CP) has been solvothermally prepared with the long and flexible N -containing tricarboxylate ligand 5-[(3-(4-carboxyphenyl)-1H-pyrazol-1-yl)methyl]isophthalic acid (H 3 L) and zinc ions. {(Me 2 NH 2 )[Zn(L)(H 2 O)]·DMF} n ( 1 ) (DMF =  N , N -dimethylformamide) exhibits a fascinating undulant two dimensional (2D) layered structure and adjacent layers are further linked by π-π interactions to form three dimensional (3D) frameworks with the rhombic channels along the b axis, in which the (Me 2 NH 2 ) + cations are located. 1 emits blue light in solid state and possesses highly stability in different organic solvents. Moreover, it exhibits excellent luminescent sensing properties for Fe 3+ and Cr 2 O 7 2− with high sensitivity and selectivity, respectively. The K sv value of Fe 3+ ions is 2.06 × 10 4  M −1 , while 1.35 × 10 4  M −1 for Cr 2 O 7 2− ions. The luminescence quenching can be attributed to resonance energy transfer between 1 and analytes. Furthermore, the lanthanide ions doped materials Ln 3+ @ 1 are successfully prepared by cation-exchange, in which Eu 3+ /Tb 3+ codoped materials show tunable luminescence and white-light emission by adjusting different molar ratios of Eu 3+ and Tb 3+ ions. [ABSTRACT FROM AUTHOR]

A series of Ce 3+ /Tb 3+ /Sm 3+ doped SrAl 2 Si 2 O 8 phosphors were synthesized by a solid state reaction. The phase and luminescence of the synthesized phosphors were investigated. The XRD patterns of the synthesized phosphors indicate that the doped rare earth ions do not change the phase structure of SrAl 2 Si 2 O 8 host. For Ce 3+ , Tb 3+ and Sm 3+ singly doped SrAl 2 Si 2 O 8 phosphors, emission bands locating at blue, green and red regions were observed, which are characteristic emission bands of Ce 3+ , Tb 3+ and Sm 3+ . For Ce 3+ /Tb 3+ and Ce 3+ /Sm 3+ codoped SrAl 2 Si 2 O 8 phosphors, energy transfer occurred between Ce 3+ /Tb 3+ ion pairs but it was forbidden between Ce 3+ /Sm 3+ ion pairs. And for Ce 3+ /Tb 3+ /Sm 3+ triply doped SrAl 2 Si 2 O 8 phosphors, energy transfer from Ce 3+ to Sm 3+ through Tb 3+ chain was accomplished. [ABSTRACT FROM AUTHOR]

Green emitting YPO 4 :Tb 3+ and orange-red emitting YPO 4 :Tb 3+ , Eu 3+ phosphors were prepared by conventional solid-state reaction and characterized in order to develop materials for applications in white light-emitting diodes (w-LED). First, the doping level of singly doped YPO 4 :Tb 3+ was systematically increased in order to obtain the highest green-to-blue emission intensity ratio through the quenching of the 5 D 3 emission, by maintaining an acceptable degree of total luminescence. The best emission performance, in terms of color purity and intensity, was obtained with a 5 mol% concentration. Starting from this result, we have synthesized and measured the emission properties of the co-doped phosphors and investigated the Tb 3+ to Eu 3+ energy transfer (ET) mechanism. The possibility of tuning the color of the luminescence by properly adjusting Eu 3+ concentration was finally discussed. [ABSTRACT FROM AUTHOR]

The Ce3+/Eu2+ activated Ba 3 YB 3 O 9 and Ba 1·5 Sr 1·5 YB 3 O 9 phosphors were prepared using solid state reactions under the reducing atmosphere. Then, their phase and fluorescence performance were investigated carefully. The XRD measurements demonstrate that the synthesized phosphors have the single phase. For the Ce3+/Eu2+ single activated Ba 3 YB 3 O 9 and Ba 1·5 Sr 1·5 YB 3 O 9 phosphors, they respectively show blue and yellow emission, meaning it is possible to generate white light by the Ce3+/Eu2+ coactivated phosphors. Due to the Ce3+ → Eu2+ energy transfers, tunable luminescence was generated by the Ce3+/Eu2+ coactivated Ba 3 YB 3 O 9 and Ba 1·5 Sr 1·5 YB 3 O 9 phosphors. The light of most of the Ce3+/Eu2+ coactivated Ba 3 YB 3 O 9 and Ba 1·5 Sr 1·5 YB 3 O 9 phosphors locates in the white light region. In addition, the substitution of Sr2+ to Ba2+ benefits to obtain the full spectrum white light. • Design of (Ba, Sr) 3 YB 3 O 9 :Ce3+/Eu2+ phosphors. • Tunable white light by substitutions of Sr2+ to Ba2+ in Ba 3 YB 3 O 9 :Ce3+/Eu2+ phosphors. • Potential applications of the (Ba, Sr) 3 YB 3 O 9 :Ce3+/Eu2+ phosphors in pc-WLEDs. [ABSTRACT FROM AUTHOR]

Sr 3 B 2 O 6 :Ce 3+ , Sr 3 B 2 O 6 :Dy 3+ and Sr 3 B 2 O 6 :Ce 3+ /Dy 3+ phosphors were synthesized by a solid state reaction. The phase, excitation and emission spectra, decay curves and energy transfer were investigated and discussed. For Sr 3 B 2 O 6 :Ce 3+ and Sr 3 B 2 O 6 :Dy 3+ phosphors, emission bands originating from transitions of Ce 3+ and Dy 3+ are observed. There is an obvious overlap between the emission spectrum of Sr 3 B 2 O 6 :Ce 3+ and excitation spectrum of Sr 3 B 2 O 6 :Dy 3+ , which suggests the possible energy transfer from Ce 3+ to Dy 3+ in Sr 3 B 2 O 6 host. The emission spectra of Sr 3 B 2 O 6 :Ce 3+ /Dy 3+ phosphors consist of emission bands corresponding to Ce 3+ and Dy 3+ . The luminescence properties of Sr 3 B 2 O 6 :Ce 3+ /Dy 3+ phosphors confirm the energy transfer from Ce 3+ and Dy 3+ in Sr 3 B 2 O 6 host. The CIE and CCT values of Sr 3 B 2 O 6 :Ce 3+ /Dy 3+ phosphors demonstrate that the Sr 3 B 2 O 6 :Ce 3+ /Dy 3+ phosphors can be used in home application of white light and commercial white lighting purposes. [ABSTRACT FROM AUTHOR]

• Crystallization induces incorporation of Tm3+/Dy3+/Zn2+ in the Al 4 B 2 O 9 lattice. • Appropriate heat treatment enhanced luminescence emission. • Crystalization promotes energy transfer from Tm3+ to Dy3+. Tm3+/Dy3+-doped glass ceramic (GC) phosphors containing Al 4 B 2 O 9 nanocrystallites were prepared by isothermal heat-treatment of aluminoborosilicate glass and the structure, optical properties were characterized. The GCs with Tm3+/Dy3+ luminescent center incorporated in the lattice of Al 4 B 2 O 9 nanocrystals reveal notable energy transfer from Tm3+ to Dy3+ and possess comparable thermal stability. The luminescence emission shift from cool white light to warm white light with increasing concentration ratio of Dy3+/Tm3+ and crystallinity. With extending heat-treatment time, the luminescence emission of GC increase firstly followed by decline in addition that the energy transfer efficiency increases whereas contrarily the lifetime decreases. Crystallization induced Dy3+/Tm3+ penetrating Al 4 B 2 O 9 is proposed to enhance the ligand field environment at luminescence center and further the energy transfer from Tm3+ to Dy3+. By adjusting concentration ratio of Dy3+/Tm3+ and the heat-treatment time, The doped GC phosphor with suitable chromaticity coordinate and prominent fluorescence potential for white light-emitting applications can be achieved. [ABSTRACT FROM AUTHOR]

NaCaBO 3 :Eu 2+ and NaCaBO 3 :Eu 2+ /Mn 2+ phosphors have been synthesized successfully through a solid state reaction. The phase and luminescent properties of the obtained phosphors also have been studied carefully. The X-ray powder diffraction (XRD) patterns suggest that all of obtained phosphors have the pure orthorhombic structure of NaCaBO 3 . Under the excitation of 330 nm, NaCaBO 3 :Eu 2+ phosphors show a single emission band in blue-green region. Under the excitation of 330 nm, NaCaBO 3 :Eu 2+ /Mn 2+ phosphors exhibit two emission bands peaking at about 477 nm and 602 nm, which originate from the Eu 2+ and Mn 2+ ions, respectively. The tunable luminescence is obtained for NaCaBO 3 :Eu 2+ /Mn 2+ phosphors by adjusting the concentrations of Eu 2+ and Mn 2+ ions. The tunable luminescence is induced by the energy transfer from Eu 2+ to Mn 2+ in NaCaBO 3 host, which is confirmed by the spectral overlap between the emission band of NaCaBO 3 :Eu 2+ and the excitation band of NaCaBO 3 :Mn 2+ and the decreasing lifetimes of Eu 2+ emission with the increasing Mn 2+ concentrations. [ABSTRACT FROM AUTHOR]

Dy 3+ and Eu 3+ codoped KSr 4 (BO 3 ) 3 phosphors were successfully synthesized by solid-state reaction process. Under near-ultraviolet (near-UV) excitation, individual Dy 3+ or Eu 3+ ion activated sample exhibits characteristic emissions in their respective regions. In KSr 4 (BO 3 ) 3 :Dy 3+ , x Eu 3+ phosphors, the energy transfer from Dy 3+ to Eu 3+ was revealed to be resonant type by dipole–dipole mechanism. And the critical distance R Dy–Eu was calculated to be 13.95 Å. The energy transfer efficiency of KSr 4 (BO 3 ) 3 :Dy 3+ , x Eu 3+ reached about 20% when the concentration of Eu 3+ was 0.035. Moreover, the emitting colors of Dy 3+ and Eu 3+ codoped samples can be adjusted from the edge of white area to warm white via tuning the activator (Eu 3+ ) doped concentration. More significantly, the chromaticity coordinates (0.334, 0.351) of KSr 4 (BO 3 ) 3 :0.005Dy 3+ , 0.015Eu 3+ sample are extremely adjacent to standard white light (0.33, 0.33). The quantum efficiency of the KSr 4 (BO 3 ) 3 :0.005Dy 3+ , 0.015Eu 3+ phosphor with 389 nm excitation is found to be 42%, demonstrating that the obtained single-component white-emitting phosphor exhibits potential applications for solid state lighting. [ABSTRACT FROM AUTHOR]

Ultra-broadband Vis-NIR (visible to near-infrared) tunable emitting phosphors are considered to the most promising fluorescent materials, such as for the applications in general lighting, NIR spectroscopy, plant growth lighting, and etc. Herein, Ce3+-Cr3+ co-doped Mg 3 Y 2 Ge 3 O 12 phosphors were prepared. Ultra-broadband Vis-NIR luminescence of Ce3+/Cr3+ ranging from ∼500 nm to >900 nm can be observed, which can be tuned with changes of doping concentration or experimental temperature. The energy transfer processes of Ce3+-Cr3+ are investigated by applying the excited state dynamics principle. Interestingly, broadband high-sensitivity temperature sensing performance is obtained for the Ce3+-Cr3+ co-doped Mg 3 Y 2 Ge 3 O 12 phosphors at high temperatures, achieving visible to near-infrared temperature regulation. A single phase phosphor-converted light emitting diode (pc-LED) was fabricated by combining blue LED chip with Mg 3 Y 2 Ge 3 O 12 :Ce3+,Cr3+ phosphors. The interesting results indicate that the prepared phosphors may realize multifunctional advanced applications. • We obtained ultra-broadband Vis-NIR luminescence of Ce3+/Cr3+ ranging from ∼500 nm to >900 nm. • A broadband high-sensitivity temperature sensing performance with S r from 1.38% K−1 to 0.85% K−1 is obtained. • A full-spectrum pc-LED fabricated by only using Mg 3 Y 2 Ge 3 O 12 :Ce3+,Cr3+ can generate white light and broadband NIR light. [ABSTRACT FROM AUTHOR]

Tuning the luminescence of phosphors is extremely important in controlling and processing light for active components of light sources, optical sensing, display devices, and biomedicine. So far, conventional chemical approaches have routinely been employed to modify the luminescence during the phosphor's synthesis. It is interesting to broaden the modulation of luminescence by physical methods, such as electric field, magnetic field, mechanical stress, temperature, photons, ionizing radiation, and so on. Since some physical methods may provide unusual routes to tune the luminescence in in‐situ, real‐time, dynamical and reversible manners, it should be beneficial for our understanding the fundamentals of luminescence and widespread applications in a variety of advanced optical materials and devices. In this review, a unified picture and primary physical strategies used for tuning the luminescence are provided. An attempt is made to review recent advances of tuning the luminescence in a wide range of phosphors, including metal‐ion‐doped compounds, semiconductors, 2D layered nanomaterials, and stimuli‐responsive organic phosphors. Lastly, some potential directions of challenging issues in this exciting field are suggested. [ABSTRACT FROM AUTHOR]

New Sm 3+ activated Tb 2 − x Sm x (MoO 4 ) 3 nanophosphors were synthesized through sol–gel method. The structural and luminescence properties have been studied by XRD, TEM and photoluminescence measurements. The XRD pattern confirms that the Tb 2 − x Sm x (MoO 4 ) 3 crystallizes in the same orthorhombic structure of Tb 2 (MoO 4 ) 3 . The spectroscopic and laser parameters of Sm 3+ ion in Tb 2 − x (MoO 4 ) 3 matrix were evaluated for the first time using Judd–Ofelt theoretical analysis. The higher value of stimulated emission cross-section of 4 G 5/2 → 6 H 7/2 transition of Sm 3+ is favorable for low threshold and high gain to obtain continuous wave laser action. The photoluminescence excitation spectra suggest that this novel phosphor can be excited over a broad range from nUV to blue light (300–490 nm). Under the excitation of UV, Tb 2 − x Sm x (MoO 4 ) 3 nanophosphor exhibits the characteristic emissions of Tb 3+ and Sm 3+ . By varying the doping concentration of Sm 3+ , the emission color of the phosphors can be tuned and white emission in a single composition can be obtained under host excitation, in which an energy transfer from MoO 4 2 − → Sm 3+ / Tb 3+ and Tb 3+ → Sm 3+ was observed. The investigation of the luminescence decay curves and lifetime values implies the energy transfer between Tb 3+ → Sm 3+ and confirms the absence of Sm 3+ → Tb 3+ energy transfer. These phosphors might be a promising material for use in nUV LEDs and can exhibit tricolor luminescence under single excitation wavelength. [ABSTRACT FROM AUTHOR]

A series of Bi3+/Tb3+/Eu3+ doped NaYGeO 4 phosphors were synthesized via the solid state sintering at 1300 °C for 3 h. The phase and luminescence performance of the synthesized phosphors were investigated. The Bi3+, Tb3+ and Eu3+ single doped NaYGeO 4 phosphors show the prominent blue, green and red emission, respectively. And the emission shows obvious dependence on doping concentration and excitation wavelength. The Bi3+ → Tb3+/Eu3+ energy transfers were confirmed by the luminescence characteristics of the Bi3+/Tb3+, Bi3+/Eu3+ and Bi3+/Tb3+/Eu3+ doped NaYGeO 4 phosphors. The Bi3+ → Tb3+ energy transfer in the NaYGeO 4 :Bi3+/Tb3+ phosphors leads to the tunable emission from the blue to cyan-green light region and the Bi3+ → Eu3+ energy transfer in the NaYGeO 4 :Bi3+/Eu3+ phosphors leads to the tunable emission from the blue to purple-red light region. But in the NaYGeO 4 :Bi3+/Tb3+/Eu3+ phosphors, the Bi3+ → Tb3+/Eu3+ energy transfers lead to the tunable emission from the blue to yellow light region through the white light region. From the luminescence characteristics of the Bi3+/Tb3+/Eu3+ doped NaYGeO 4 phosphors, the energy transfer mechanisms were speculated. • The excellent luminescence characteristics for the NaYGeO 4 based phosphors. • Dual energy transfer induced white light for the NaYGeO 4 :Bi3+/Tb3+/Eu3+ phosphors. • The wide tuning range of the doping concentration for the white light phosphors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of CsPbBr 1.5 I 1.5 @SrHAp composites were obtained by a hot injection method. • The formation mechanism of the nanocomposites was investigated in detail. • The color-tunable luminescence can be realized from blue through white and to yellow. • The thermal stability and emission intensity are improved by integrating SrHAp matrix. • The WLED device can exhibit bright white light with good CIE coordinate, CCT, and CRI. A variety of novel CsPbBr 1.5 I 1.5 @SrHAp nanocomposites have been fabricated by a facile one-pot hot injection method for the first time. An electrostatic interaction mechanism has been proposed to realize the in-situ growth of CsPbBr 1.5 I 1.5 perovskite quantum dots (PQDs) on SrHAp [strontium hydroxyphosphate, Sr 5 (PO 4) 3 OH] nanorods with negatively charged surfaces, which have been proved by the XRD, XPS, TEM, FT-IR, and density functional theory (DFT). The incorporation of SrHAp matrix for CsPbBr 1.5 I 1.5 not only greatly enhances the thermal and spectral stability but also increases the emission intensity of the CsPbBr 1.5 I 1.5 PQDs. More importantly, the fascinating color-tunable luminescence performance from blue through white and eventually toward yellow light can be realized in a single phase by simply changing the amounts of SrHAp matrix or excitation wavelengths. Thus, the CsPbBr 1.5 I 1.5 @SrHAp single-phase white light emitting phosphor can be obtained with excellent chromaticity coordinate (x, y) and CCT in the warm white region [(0.328, 0.340), 5698 K], which is close to the daily use of pure white light. The as-prepared LED device can exhibit dazzling white light emission by integrating CsPbBr 1.5 I 1.5 @SrHAp nanocomposite into a 365 nm UV LED chip, which indicates that the as-obtained CsPbBr 1.5 I 1.5 @SrHAp single-phase white emitting phosphor could be regarded as potential candidates for WLEDs. [ABSTRACT FROM AUTHOR]

Eu2+ and Eu3+ codoped alkaline-earth aluminum borates MAl 2 B 2 O 7 :Eu (M = Ca2+, Sr2+ , and Ba2+) phosphors were prepared by a conventional high-temperature solid-state method. The phosphor exhibits strong absorption in the spectral range of ∼200–450 nm and bright tunable emission in the blue region, white region, and red region. The effect of composition, excitation wavelength, and doping concentration of europium ion on luminescence behavior of the phosphors were investigated systematically. Upon 254 nm excitation, SrAl 2 B 2 O 7 :Eu exhibits blue and bluish-green emission of Eu2+ and red emission of Eu3+. Ca2+ substitution for Sr2+ promoted the optimization of luminescence quality , and even the emergence of white light with chromatic coordination (0.382, 0.234), and Ba2+ substitution for Sr2+ increased the total luminescence intensity by ∼12.5 times. The changes in luminescence behavior were explained according to the structural defect of the phosphor and the site symmetry of the europium ions. The tunable luminescence and white-light emission upon 254 nm excitation imply that the phosphors have potential application prospects in cold cathode fluorescent lamps. • Phosphors exhibit tunable luminescence upon 254 nm excitation. • Luminescence behaviors are explained by composition, defects, and site symmetry. • Phosphor show potential implication in cold cathode fluorescent lamp. [ABSTRACT FROM AUTHOR]

The Ce3+ and/or Eu2+ doped inorganic phosphors with the broad excitation bands and efficient visible emission play the important roles in the light emitting diodes. Herein, we synthesized the Ce3+/Eu2+ doped Sr 3 Y 2 Ge 3 O 12 phosphors via a molten salt method under a reducing atmosphere. The phosphors were investigated by the X-ray diffraction, scanning electron microscopy, transmission electron microscopy and fluorescence spectrophotometer. The thermal stability of the Sr 2.91 Ce 0.03 Eu 0.06 Y 2 Ge 3 O 12 phosphor was evaluated in 300–500 K at a temperature interval of 25 K. Upon the excitation at 450 nm, the Sr 2.97 Ce 0.03 Y 2 Ge 3 O 12 and Sr 2.97 Eu 0.03 Y 2 Ge 3 O 12 phosphors emit green and yellow-red light, respectively. The energy transfer process from Ce3+ to Eu2+ occurs in Ce3+/Eu2+ codoped Sr 3 Y 2 Ge 3 O 12 phosphors, which results in the tunable luminescence. • Molten salt synthesis of the Sr 3 Y 2 Ge 3 O 12 :Ce3+/Eu2+ phosphors at a low temperature. • Luminescence characteristics of the Sr 3 Y 2 Ge 3 O 12 :Ce3+/Eu2+ phosphors. • Energy transfer processes from Ce3+ to Eu2+ in the Sr 3 Y 2 Ge 3 O 12 host. [ABSTRACT FROM AUTHOR]

In this work, a simple method to prepare orange-red phosphor is introduced. A series of y at.% Eu3+-doped Gd(Nb x P 1-x)O 4 (x = 0%, 1%, 2%, 3%, 4%, 5%, 6%, 10% and y = 5%, 7%, 9%, 11%, 13%, 14%, 15%) phosphors were prepared through solid reaction technique. The structure and optical properties of the phosphors were characterized using measurements of X-ray powder diffraction, photoluminescence excitation, photoluminescence and decay curves. The X-ray diffraction results revealed that the obtained phosphors possessed the same pure monoclinic phase as GdPO 4 until the doping concentration of Nb5+ reached a maximum value of 5 at.%. With the high sensitivity of the 5D 0 →7F 2 transition to the symmetry of the crystal field, the relative intensity of the two emission peaks at 596 and 615 nm could be continuously adjusted by changing the Nb5+ concentration. Moreover, Judd–Ofelt calculations performed on samples doped with different Eu3+ ions concentrations showed their promise as color-tunable orange-red phosphors. • A series of Eu3+:Gd(Nb x P 1-x)O 4 phosphors with gap type were synthesized. • The energy transfers among Gd3+, NbO 4 3− and Eu3+ were analyzed in detail. • Emission intensity of 596 and 615 nm can be regulated by contents of Nb5+ ions. [ABSTRACT FROM AUTHOR]

The researches on cyan phosphors those can be effectively excited by near-ultraviolet (NUV) light are being hot topics lately because that they have potential applications in phosphor converted white light emitting diodes (pc-WLEDs) based on the NUV chips. In this work, Bi3+/Dy3+ doped Ca 2 LaTaO 6 phosphors were prepared through a solid state reaction procedure, and their luminescence characteristics were investigated through the measurements of the luminescence spectra and the decay curves. The excitation spectra indicate that the Bi3+ or Dy3+ single doped and Bi3+/Dy3+ codoped Ca 2 LaTaO 6 phosphors are suitable for NUV excitation due to the excitation spectra within 250–500 nm. The emission spectra show that the lights of Bi3+/Dy3+ codoped Ca 2 LaTaO 6 phosphors locate in cyan region. The ptotoluminescence characteristics indicate that they have possible uses in pc-WLEDs based on NUV chips. • The broad blue emission of Ca 2 LaTaO 6 :Bi3+ phosphors. • The cyan emission of Ca 2 LaTaO 6 :Bi3+/Dy3+ phosphors due to Bi3+.→ Dy3+ energy transfer • The potential applications of Bi3+/Dy3+ doped Ca 2 LaTaO 6 in NUV based pc-WLEDS. [ABSTRACT FROM AUTHOR]

In this work, Tb3+ or Eu3+ single doped and co-doped La 2 W 3 O 12 were synthesized via a solid-state reaction at 900 °C. The crystal structure and photoluminescence properties were systematically investigated in detail. It was found that the La 2 W 3 O 12 based on the advantages of WO 4 groups exhibits a broad absorption cross-section in the ultraviolet area, which can effectively enhance the emission intensity of Tb3+ and Eu3+. The energy transfer from Tb3+ to Eu3+ is determined by the dipole-dipole mechanism, and the energy transfer efficiency from Tb3+ to Eu3+ is as high as 36%. Based on efficient energy transfer effect, multicolor tunable emission from green to yellow and eventually toward red is realized. In addition, the temperature-dependent luminescence of La 2 W 3 O 12 : Tb3+, Eu3+ are carefully investigated, which suggested that as-prepared La 2 W 3 O 12 : Tb3+, Eu3+ phosphors are excellent candidates for solid-state laser, panel display, WLEDs and LED plant lights. [Display omitted] • A prepared novel tungstate Tb3+/Eu3+ co-doped LWO phosphors have good thermal stability and luminescence performance. • The energy transfer mechanism from Tb3+ to Eu3+ was determined to be a dipole-dipole mechanism. • Multicolor tunable emission from green through yellow and eventually to red is realized under UV light excitation. [ABSTRACT FROM AUTHOR]

Researches on tunable luminescence and temperature sensitivity of phosphors have become an increasingly popular trend. This paper reports a series of Ca 2 YZr 2 Al 3 O 12 (CYZA):Bi3+, Sm3+ phosphors prepared by solid-state reaction. The phase purity, energy transfer, luminescent properties and temperature sensing performance of the phosphors have been carefully studied. CYZA:Bi3+, Sm3+ phosphors excited by ultraviolet light show tunable color emission, and the color shifts from dark blue to pink due to Bi3+→Sm3+ energy transfer. The related luminescent mechanism of phosphors is also explained. In addition, according to the different thermal sensitivity of Bi3+ and Sm3+, the temperature sensitivity of the phosphors is studied by fluorescence intensity ratio model. The maximum values of absolute sensitivity and relative sensitivity reach up to 0.099% K−1 at 423 K and 0.356% K−1 at 473 K, respectively. These findings indicate that CYZA:Bi3+, Sm3+ phosphors are potential candidates for tunable luminescence and temperature sensing. • The color-tunable property can be obtained in CYZA:Bi3+, Sm3+ phosphors. • Energy transfer from Bi3+ to Sm3+ ions. • Different thermal attenuation behaviors of Bi3+ and Sm3+ ions. • Temperature sensing performance is investigated by FIR model. [ABSTRACT FROM AUTHOR]

• New solid solutions Ca 8 M Tb 1 –x Eu x (PO 4) 7 (M = Mg2+, Zn2+, Ca2+; 0 ≤ x ≤ 1) were synthesized and studied in detail. • The highest integral intensity was registered for Zn doped host and increases the luminescence intensity by 15%. • The effective energy transfer from Tb3+ → Eu3+ was detected and characterized. • Synthesized samples are perspective single-phase phosphors. A series of Ca 8 M Tb 1 –x Eu x (PO 4) 7 (M = Mg2+, Zn2+, Ca2+; 0 ≤ x ≤ 1) with β-Ca 3 (PO 4) 2 -type structure have been synthesized via a standard solid-state method. X-ray diffraction, second harmonic generation, photoluminescence emission and excitation spectra, and decay time curves were used to characterize solid solutions. The color coordinates of as -prepared samples can be shifted from green to red regions by the increasing of Eu3+ concentration. Red-to-orange (R/O) and green-to-blue (G/B) factors indicate a higher local symmetry of emitting Eu3+ and Tb3+ ions environment in Ca 8 M Tb 1– x Eu x (PO 4) 7 (M = Mg, Zn) in comparison to Ca 9 Tb 1 –x Eu x (PO 4) 7. The study shows that Zn-incorporation in the β-Ca 3 (PO 4) 2 matrix increases the luminescence intensity by 15%. The presented results indicate that the synthesized solid solutions can be considered as new single-phase phosphors. [ABSTRACT FROM AUTHOR]

Research process of phosphors with color-tunable luminescence properties has been a research hotspot in the field of high-quality white light emitting diodes. Herein, this paper report that a series of Tb3+ doped and Tb3+, Eu3+ co-doped Ca 2 YZr 2 Al 3 O 12 phosphors were successfully prepared by the traditional solid-state reaction in air atmosphere. The crystal structure, optical performance and thermal quenching behavior were investigated in detail. CYZA: Tb3+, Eu3+ phosphors exhibited tunable color emission from green to yellow to red on the basis the energy transfer of Tb3+→Eu3+ under n-UV excitation. More impressively, as-prepared samples possess high thermal stability comparable or even superior to Lu 3 Al 5 O 12 : Ce3+ via designing the ratio of Tb3+/Eu3+ based on energy transfer. Influence mechanism of Eu3+ on the thermal stability of CYZA: Tb3+ was illustrated. The as-fabricated w-LED device shows a warm white light with high CRI (86.4) at CCT of 3431K. These results suggest its great potential as an excellent luminescent material for the design of warm white solid-state lighting. • CYZA: Tb3+, Eu3+ phosphors were prepared for the first time by solid-state reaction route. • The emitting-color of CYZA: Tb3+, Eu3+ was tunable by adjusting ratio of Tb3+/Eu3+. • The introduction of Tb3+ significantly improves thermal stability, Eu3+ does the opposite. • The mechanism of Tb3+.→Eu3+ energy transfer was investigated. [ABSTRACT FROM AUTHOR]

A series of blue-green emitting NaBaBO 3 :Ce3+, Tb3+ phosphors were synthesized via conventional high temperature solid-state reaction method. The crystal structure, luminescence properties, energy transfer processes and the properties of the packing LED device were investigated. The phosphors present tunable luminescence in the blue-green region due to the energy transfer from Ce3+ to Tb3+. The internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the composition optimized NaBaBO 3 :0.01Ce3+, 0.03 Tb3+ phosphor reached 57% and 36%, respectively. Using a 365 nm NUV LED chip combining with NaBaBO 3 : 0.01Ce3+, 0.03 Tb3+ phosphor and CaAlSiN 3 :Eu2+ red phosphor, a high quality white light was obtained with CIE chromaticity coordinates of (0.316, 0.307), CCT of 6473 K, and CRI of 81.4. These results demonstrated that NaBaBO 3 :Ce3+,Tb3+ phosphors is a promising blue-green phosphor for NUV white LEDs. • The energy transfer of Ce3+→Tb3+ in NaBaBO 3 phosphors has been confirmed. • Quantum efficiency has been calculated. • The emission colors can be varied from blue to blue-greenish through controlling Tb3+ concentrations. • Potential candidates to be used as blue-green phosphor for NUV excited white LEDs. [ABSTRACT FROM AUTHOR]

A series of lanthanide activator ions (Ln3+) doped bismuth silicate Bi 4 Si 3 O 12 phosphors have been fabricated via the Pechini sol−gel route. The as-synthesized eulytite structured Bi 4 Si 3 O 12 sample which exhibits intense green-blue emission is beneficial for host materials of lanthanide activator ions. When the Ln3+ ions (Sm3+, Dy3+, or Eu3+) are doped into the Bi 4 Si 3 O 12 host, an insufficient energy transfer occurs from the host matrix to Ln3+ ions, which can be confirmed by the photoluminescence spectra and decay lifetimes of the Ln3+ doped samples. The as-synthesized Bi 4 Si 3 O 12 :Ln3+ phosphors show both the intrinsic broad band luminescence of Bi 4 Si 3 O 12 host and the characteristic sharp peak emissions of Ln3+ ions, which can generate the tunable multicolor emissions in a single-phase phosphor by adjusting the Ln3+ doping concentrations. More importantly, three kinds of Ln3+-doped single-phase white light emitting phosphors with excellent chromaticity coordinate (x, y) and CCT in the warm white region [Sm3+: (0.336, 0.330), 5315 K; Dy3+: (0.330, 0.370), 5614 K; Eu3+: (0.340, 0.307), 5034 K] can be obtained when the doping concentrations of Sm3+, Dy3+, and Eu3+ are fixed at 0.5, 5, and 1 mol%, which are quite close to the daily use of pure white light. By integrating the Bi 4 Si 3 O 12 :Ln3+ phosphors into a 280 nm UV LED chip, all the fabricated WLED devices can exhibit bright white light emission, which provides direct evidence that the as-synthesized BSO:Ln3+ (Ln = Sm, Dy, and Eu) single-phase white-emitting phosphors have great potential for WLEDs and optoelectronic devices. Image 1 • A series of Ln3+ doped Bi 4 Si 3 O 12 phosphors have been fabricated via a sol-gel route. • An insufficient energy transfer occurs from the Bi 4 Si 3 O 12 host matrix to Ln3+ ions. • The single-phase Bi 4 Si 3 O 12 :Ln3+ phosphors can generate tunable multicolor emissions. • Three white light phosphors can be obtained with good CIE coordinate and CCT. • The WLED devices fabricated by the phosphors can exhibit bright white light emission. [ABSTRACT FROM AUTHOR]

Sm3+, Tb3+ and Sm3+/Tb3+ doped Ba 3 MgSi 2 O 8 phosphors were prepared by molten salts synthesis technique using NaCl/KCl mixture as the flux. The phase and optical characteristics of the prepared phosphors were researched. The XRD results revealed that the prepared phosphors have the pure Ba 3 MgSi 2 O 8 phase. For Sm3+ or Tb3+ singly doped Ba 3 MgSi 2 O 8 phosphors, they show characteristic emission bands of Sm3+ (exciting at 405 nm) or Tb3+ (exciting at 233 nm) ions. Exciting at 233 nm, Sm3+/Tb3+ codoped Ba 3 MgSi 2 O 8 phosphors show emission band corresponding to Sm3+ and Tb3+ ions. Tb3+ → Sm3+ energy transfers occur in Sm3+/Tb3+ codoped Ba 3 MgSi 2 O 8 phosphors, which leads to the tunable luminescence of them. The CIE coordinates change from (0.431, 0.515) for Ba 3 MgSi 2 O 8 :0.12 Tb3+/0.01Sm3+ to (0.555, 0.425) for Ba 3 MgSi 2 O 8 :0.12 Tb3+/0.05Sm3+. The color of light changes from green-yellow for Ba 3 MgSi 2 O 8 :0.12 Tb3+/0.01Sm3+ to red-yellow for Ba 3 MgSi 2 O 8 :0.12 Tb3+/0.05Sm3+. • Molten salts preparation of Sm3+, Tb3+ and Sm3+/Tb3+ doped Ba 3 MgSi 2 O 8 phosphors. • Energy transfer from Tb3+ to Sm3+ in Sm3+/Tb3+ codoped Ba 3 MgSi 2 O 8 phosphors. • Tunable luminescence of Sm3+/Tb3+ codoped Ba 3 MgSi 2 O 8 phosphors. [ABSTRACT FROM AUTHOR]

A series of emission-tunable Ba 3- x Sc(BO 3) 3 : x Eu2+ (0 ≤ x ≤ 0.15) and Ba 2.97- y Gd y Sc 1- y Mg y (BO 3) 3 : 0.03Eu2+ (0 ≤ y ≤ 0.15) phosphors were synthesized by a solid-state method. Structure analysis of X-ray powder diffraction (XRD) and Rietveld refinement show that Eu2+ ions occupy randomly at Ba sites of hexagonal lattice with space group P6 3 cm. Photoluminescence emission spectra and the decay curves of phosphors demonstrated the existence of multiple Eu2+ emitting centers. Eu2+ ions occupy at four Ba sites of Ba 3- x Sc(BO 3) 3 : x Eu2+ (0.03 ≤ x ≤ 0.15) emit orange light (λem = 670 nm and 560 nm) through 370 nm UV excitation. The broader absorption band, ranging from 220 nm to 550 nm, matches well with the near-ultraviolet LED chips. Furthermore, color tuning from orange to red is successfully achieve by the double doping of Gd3+-Ba2+ and Mg2+-Sc3+ in Ba 2.97 Sc(BO 3) 3 : 0.03Eu2+. Our results indicate that red emission Ba 3 Sc(BO 3) 3 : Eu2+ phosphors is an ideal candidate for the application in white light-emitting diodes. Image 1 • Eu2+ ions occupied at four Ba sites for Ba 3 Sc(BO 3) 3 :Eu2+ emit orange light. • Broader absorption band (220–550 nm) matches well with the n-UV LED chips. • Decay curves prove the existence of energy transfer among multiple Eu2+ centers. • Color tuning is successfully realized by the Gd3+/Mg2+ double substitution. [ABSTRACT FROM AUTHOR]

Herein, Ce3+ and Ce3+/Dy3+ co-doped Ca 3 Al 2 O 6 phosphors have been designed and synthesized via a facile citrate-based sol-gel technique, and their structural, photoluminescence properties and energy transfer phenomenon were investigated comprehensively. The XRD analysis indicated that pure Ca 3 Al 2 O 6 phase can be synthesized at low temperature (1000 °C) for merely 2 h. The photoluminescence spectra showed the dominant emission of Ce3+ singly doped phosphors is located in the blue region even at low Ce3+ doping level, which indeed favors the energy transfer from Ce3+ to other luminescent centers. When Dy3+ is co-doped into Ca 3 Al 2 O 6 :Ce3+ phosphors, the remarkable sensitizing effect of Ce3+ on Dy3+ is validated by comparatively analyzing the excitation, emission spectra and average lifetimes of the series of samples. Through the concentration quenching theory, the critical distance between Ce3+ and Dy3+ is calculated to be 13.50 Å. Furthermore, the energy transfer mechanism between them is most likely ascribed to electric dipole-dipole interaction. In virtue of the variation of the emission intensities of Ce3+ and Dy3+, the emitting colors of Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors can realize tunable luminescence from deep blue to bluish-white region through controlling the Dy3+ content. Based on these analysis, Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors could potentially be applied as a single-phase color-tunable phosphors pumped by near-ultraviolet (n-UV) radiation. • Developed a facile sol-gel method to prepare successfully Ca 3 Al 2 O 6 compound. • The blue emission of as-prepared Ca 3 Al 2 O 6 :Ce3+ phosphors dominates, which favors the energy transfer process. • The possible mechanism for the dominance of blue emission was discussed. • The energy transfer phenomenon in Ca 3 Al 2 O 6 :Ce3+, Dy3+ phosphors was investigated in detailed. • Ca 3 Al 2 O 6 :Ce3+, Dy3+ can serve as a single-phase color-tunable phosphors excited by near-ultraviolet radiation. [ABSTRACT FROM AUTHOR]

A novel red-emitting Na 2 Tb 0.5 (MoO 4)(PO 4):0.5Eu3+ phosphor was successfully synthesized via high temperature solid-state reaction method to explore new red emissions with high thermal stability and high colour purity. The results indicate that the alternating tetrahedrons of [PO 4 ]3- and [MoO 4 ]2- formed in the three-dimensional structure play a decisive role in isolating Tb3+ and Eu3+ ions. This structural isolation increases the concentration quenching of Tb3+ and Eu3+ in single-doped phosphors by more than 50%. In co-doped phosphors, the energy transfer from Tb3+ to Eu3+ was verified by the overlap of luminescent spectra and variations in decay curves. The emission colour of Na 2 Y 1- x - y (MoO 4)(PO 4): y Tb3+, x Eu3+ can be tuned from green to red through the energy transfer process by adjusting the ratio of Tb3+/Eu3+. The emission intensity at 150 °C is 84.7% compared to room temperature, as well as the remarkable correlated colour temperature (2425 K) and high colour purity (95.3%) with CIE chromaticity coordinates (0.654, 0.345) make Na 2 Tb 0.5 (MoO 4)(PO 4):0.5Eu3+ as an incredible red-emitting phosphor for both display devices and warm white lighting applications. Image 1 • This phosphor emits high-purity red light (95.3%), it can therefore be used in display devices. • The remarkable CCT (2425 K) also reveals the application value for warm white lighting. • The emission at 425 K is 84.7% of that at room temperature, demonstrating the excellent thermal stability and providing a reliable red light source. • The energy transfer process has been investigated to evaluate the relationship between decay curves and Eu3+ doping amount. [ABSTRACT FROM AUTHOR]