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Abstract: Charge compensation was the effective methods to enhance the luminescence properties of phosphors. In this paper, novel single‐phased orange light emitting Sr2Mg3P4O15:Eu3+ phosphors were prepared by solid state method. The phase purity and luminous characteristics were examined in detail. Meanwhile, three kinds of charge compensation methods (co‐doping the alkali metal R+ (R+ = Li, Na, and K), substituting Si4+ for P5+ and self‐compensation) were employed to solve the charge imbalance problem between Sr2+ and Eu3+. The results showed that emission intensity of Eu3+ was improved by 1.43 (Li+), 1.58 (Na+), 1.53 (K+), 1.61 (Si4+), and 1.30 (self) times than that of Sr1.6Mg3P4O15:0.40Eu3+, respectively, and there was no change in the emitting color simultaneously. Furthermore, as the temperature reached at 423 K, the emission intensity increased from 41.67% of Sr1.6Mg3P4O15:0.40Eu3+ to 55.69% (Li+), 61.62% (Na+), 58.98% (K+), 71.15% (Si4+), and 80.59% (self) of that at room temperature. The reasons of those phenomena were the reduction in ion vacancies caused by charge imbalance through the charge compensation process. The specific mechanisms were elaborated in detail. Overall, this research validated that the charge compensation strategies could be severed as the key method to improve the luminescence properties, especially the thermal stability of phosphor. [ABSTRACT FROM AUTHOR]

By substituting Gd 3+ for Ba 2+ ions in the single-phased Na 2 (Ba 5.99-2 m Eu 0.01 Gd m Na m )(Si 2 O 7 )(SiO 4 ) 2 (0 ≤ m ≤ 0.30) phosphors, the asymmetric emission peaks of three Eu luminescence centers monitored around 444, 494 and 552 nm varied accordingly under 365 nm excitation and caused the shift of CIE color coordinates from (0.1569, 0.2122) to (0.1697, 0.3082). Furthermore, the thermal stability and quantum yield of phosphors could be affected via the different cation substitution of Gd 3+ . Combined with the change tendencies of Ba-O bond lengths by Rietveld refinement, the possible mechanism of the luminescence transformation of Eu 2+ ion was the preferential occupancy at different crystallographic sites of Eu 2+ . Generally, this work sheds some new lights on the design and structure explanation of preferential occupancy at different crystallographic sites in phosphors. [ABSTRACT FROM AUTHOR]

A series of single-phased Na 2 Ba 5.99- x (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ , x Mg 2+ and Na 2 Ba 5.99- y (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ , y Zn 2+ phosphors have been successfully prepared via the solid-state reaction. Structural refinement, luminescence property, color tuning and thermally stability were systematically investigated. The as-prepared Na 2 Ba 6 (Si 2 O 7 )(SiO 4 ) 2 :0.01Eu 2+ phosphor showed broad excitation bands from 250 nm to 450 nm and presented wide emission bands under 365 nm excitation, which could be decomposed by Gaussian fitting into three peaks corresponding to different Eu luminous centers named Eu1, Eu2 and Eu3. By substituting Mg 2+ or Zn 2+ for Ba 2+ , the relative intensities of Eu1, Eu2 and Eu3 emission bands changed gradually. Combined with the variation tendencies of Ba O bond lengths by Rietveld refinement, the possible mechanism of the luminescence transformation of Eu 2+ ion was the preferential occupancy of Eu 2+ at different crystallographic sites. In addition, the introduction of Mg 2+ ion expressed more obvious improvement on the thermal quenching behaviors of Eu 2+ than Zn 2+ ion in this matrix. The emission intensities of Eu2 and Eu3 could be enhanced from 63.2% to 82.7% and 35.1%–46.8% at 373 K compared to the initial intensity when Mg 2+ concentration was 0.10. Generally, this work sheds some new lights on the design and structure explanation of preferential occupancy at different crystallographic sites in phosphors. [ABSTRACT FROM AUTHOR]

A series of trivalent rare-earth element ions (europium, terbium, dysprosium) singly- and co-doped strontium yttrium borate phosphors was synthesized via the sol–gel method. The phase formation, luminescence properties, decay times, and energy transfer behaviors from terbium ions to europium ions, the thermal stability, and the Commission Internationale de L’Eclairage coordinates were investigated. Under the excitation of ultraviolet light, the singly doped phosphors exhibited green emission of terbium ions, white emission of dysprosium ions, and red emission of europium ions, respectively. For the terbium and europium ions co-doped strontium yttrium borate samples, a white emission can be realized by blending the doping concentration of terbium and europium ions. The critical distance between terbium and europium ions has been calculated to be about 14.52 Å and the energy transfer from terbium to europium occurred through the dipole–quadrupole interaction. At 150°C, the emission intensity of terbium and europium in the 12 mol% terbium and 14 mol% europium co-doped strontium yttrium borate sample was maintained at about 74% and 87% of their corresponding initial values, respectively, and the dysprosium ions singly doped strontium yttrium borate sample showed about 70% of its initial emission intensity at room temperature. The above results suggested that europium, terbium, dysprosium ions singly- and co-doped strontium yttrium borate phosphors have potential applications as ultraviolet-convertible phosphors. [ABSTRACT FROM AUTHOR]

Monodisperse mono-concave microsphere/microflower/nanosheet GdBO 3 :Eu 3+ samples have been successfully synthesized via hydrothermal method using Gd 0.99 Eu 0.01 (OH) 3 nanorods as sacrificial precursors. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), field scanning electron microscopy (FE-SEM) and fluorescence spectrometry were used to characterize the samples. The shape of these as-prepared GdBO 3 :Eu 3+ architectures can be tuned effectively by controlling the concentrations of NaOH (C NaOH ) of the precursor solution and the amounts of PEG (20000) surfactant. As a typical morphology, the possible formation mechanism for GdBO 3 :Eu 3+ monodisperse mono-concave microsphere was presented in detail. Under ultraviolet excitation, the as-obtained GdBO 3 :Eu 3+ samples showed strong characteristic orange and red emission of Eu 3+ . Compared with samples get by solid state reaction, the samples obtained by hydrothermal method possess higher red/orange (R/O) ratio attributed to 5 D 0 − 7 F 1 and 5 D 0 − 7 F 2 transitions. The influence of diversity morphology on the R/O ratio and emission intensity has been also investigated. This work sheds some light on the design of a well-defined complex structure, and the luminescent properties have potential applications in fluorescent lamps and field emission displays. [ABSTRACT FROM AUTHOR]

A series of Eu2+ and Tb3+ singly-doped and co-doped Sr3Y2(Si3O9)2 (SYSO) phosphors have been synthesized via a conventional high-temperature solid-state reaction. The crystal structures, photoluminescence properties, fluorescence lifetimes, thermal properties and energy transfer of SYSO:Eu2+,Tb3+ were systematically investigated in detail. Rietveld structure refinement of the obtained phosphors indicated that the SYSO host crystallized in a monoclinic system with the space group C2/c (15) and there are three kinds of cation sites for the doped ions to occupy forming emission centers. The photoluminescence (PL) emission bands of SYSO:xEu2+ show a red-shift tendency with increasing Eu2+ content which should be attributed to more Eu2+ ions entering into Sr2/Y2 and Sr3/Y3 sites from the Sr1/Y1 site. For the co-doped SYSO:Eu2+,Tb3+ samples, tunable colors from cyan to green can be realized by varying the doping concentration of the Tb3+ ions. The intense green emission was realized in the SYSO:Eu2+,Tb3+ phosphors on the basis of the highly efficient energy transfer from Eu2+ to Tb3+ with an efficiency of over 89%. As a result, the emission intensity of SYSO:0.01Eu2+,0.21Tb3+ is about 2.5 times higher than that of SYSO:0.21Tb3+ under 340 nm UV excitation. The energy transfer mechanism from Eu2+ to Tb3+ in the SYSO host was ascribed to the quadrupole–quadrupole interactions. These results indicated that the SYSO:Eu2+,Tb3+ phosphors can act as single-phase green emitting phosphors for possible applications in ultraviolet light-based white light-emitting diodes (w-LEDs). [ABSTRACT FROM AUTHOR]

Abstract: Charge compensation was the effective methods to enhance the luminescence properties of phosphors. In this paper, novel single‐phased orange light emitting Sr2Mg3P4O15:Eu3+ phosphors were prepared by solid state method. The phase purity and luminous characteristics were examined in detail. Meanwhile, three kinds of charge compensation methods (co‐doping the alkali metal R+ (R+ = Li, Na, and K), substituting Si4+ for P5+ and self‐compensation) were employed to solve the charge imbalance problem between Sr2+ and Eu3+. The results showed that emission intensity of Eu3+ was improved by 1.43 (Li+), 1.58 (Na+), 1.53 (K+), 1.61 (Si4+), and 1.30 (self) times than that of Sr1.6Mg3P4O15:0.40Eu3+, respectively, and there was no change in the emitting color simultaneously. Furthermore, as the temperature reached at 423 K, the emission intensity increased from 41.67% of Sr1.6Mg3P4O15:0.40Eu3+ to 55.69% (Li+), 61.62% (Na+), 58.98% (K+), 71.15% (Si4+), and 80.59% (self) of that at room temperature. The reasons of those phenomena were the reduction in ion vacancies caused by charge imbalance through the charge compensation process. The specific mechanisms were elaborated in detail. Overall, this research validated that the charge compensation strategies could be severed as the key method to improve the luminescence properties, especially the thermal stability of phosphor. [ABSTRACT FROM AUTHOR]

By substituting Ca 2+ or Sr 2+ for Ba 2+ and Yb 3+ or La 3+ for Y 3+ , in whole or in part, the single-phased Ba 0.97- x M x Y 2 Si 3 O 10 :0.03Eu 2+ and Ba 0.97 Y 2- y RE y Si 3 O 10 :0.03Eu 2+ phosphors (M = Sr 2+ or Ca 2+ , RE = La 3+ or Yb 3+ ) were synthesized successfully via high temperature solid-state reaction method. The introduction of different cations caused higher covalence and rigidity of the as-prepared samples and enhanced the interaction between electrons around Eu 2+ ions, leading to the variation of emission color from bluish violet to light blue or greenish blue upon optimum excitation wavelength. In addition, the effect of cation substituting level on thermal stability of BaY 2 Si 3 O 10 :0.03Eu 2+ was investigated in details. The emission intensities of Ba 0.97- x Y 2 Si 3 O 10 :0.03Eu 2+ , x Sr 2+ , Ba 0.97- x Y 2 Si 3 O 10 :0.03Eu 2+ , x Ca 2+ , Ba 0.97 Y 2- y Si 3 O 10 :0.03Eu 2+ , y Yb 3+ and Ba 0.97 Y 2- y Si 3 O 10 :0.03Eu 2+ , y La 3+ varied in the range of 68.09%–78.64%, 78.44%–81.00%, 67.38%–79.90% and 60.25%–79.84% at 423 K compared to the initial intensity at room temperature, respectively. Meanwhile, the crystal filed split effect (CFSE) and nephelauxetic effect (NE) mechanisms were also proposed to better explain the red shifts and the changes of thermal quenching behavior of above samples. This work shed some light on the design of phosphors with controllable emission colors and higher thermal stability for the applications in phosphor-converted devices. [ABSTRACT FROM AUTHOR]

The novel phosphors BaZrSi 3 O 9 :Ce 3+ (BZS:Ce 3+ ) have been successfully synthesized by the conventional solid-state reaction. The phase purity and crystal structure were obtained by X-ray diffraction (XRD) measurements and Rietveld refinement. The photoluminescence spectroscopy revealed that the as-prepared phosphors exhibited a bright blue emission under the excitation by near ultraviolet light and the PL emission peaks of BZS: x Ce 3+ showed a red-shift from 432 nm to 451 nm on the Ce 3+ concentration increasing. The corresponding red-shift mechanism has been discussed. The concentration quenching behavior was observed. The luminescence decay curves and lifetime values were analyzed. This phosphor exhibited high internal quantum efficiency. Thermal quenching luminescence properties showed that the emitting intensity was remained 44.60% of that measured at room temperature when the temperature increased to 398 K. The results indicate that the BaZrSi 3 O 9 :Ce phosphor is a promising blue-emitting phosphor for the application as an ultraviolet-convertible phosphor. [ABSTRACT FROM AUTHOR]

The tunable blue-emitting KBa 1− x (Mg/Zn) x Y 0.95 (BO 3 ) 2 :0.05Ce 3+ and K 1− y Na y BaY 0.95 (BO 3 ) 2 :0.05Ce 3+ phosphors have been investigated via cation substitution of Mg 2+ /Zn 2+ for Ba 2+ and Na + for K + in KBaY(BO 3 ) 2 host. The crystal structures, photoluminescence properties, thermal stability and the effect of Mg 2+ /Zn 2+ /Na + concentration on the luminescence characteristics were investigated in detail. The XRD analysis implied that KBa 1− x (Mg/Zn) x Y(BO 3 ) 2 solid solutions were limited, while continuous solid solution was possible in K 1− y Na y BaY(BO 3 ) 2 system. Upon the excitation at 365 nm, the emission peaks of KBa 1− x (Mg/Zn) x Y 0.95 (BO 3 ) 2 :0.05Ce 3+ (0 ⩽ x ⩽ 0.6) blue-shifted from 435 to 424 nm, and K 1− y Na y BaY 0.95 (BO 3 ) 2 :0.05Ce 3+ (0 ⩽ y ⩽ 1) blue-shifted from 435 to 427 nm with the Mg 2+ /Zn 2+ /Na + doping concentration increase. The thermal stabilities of KBa 1− x (Mg/Zn) x Y 0.95 (BO 3 ) 2 :0.05Ce 3+ phosphors were enhanced from 20 °C to 200 °C by increasing the concentration of Mg 2+ and Zn 2+ . The substitution of Na + for K + led to a decrease in the proportion of 5 D- 2 F 5/2 and 5 D- 2 F 7/2 corresponding to the Gaussian fitting of Ce 3+ in K 1− y Na y BaY 0.95 (BO 3 ) 2 :0.05Ce 3+ phosphors. At the temperature increased, the full width at half maximum of photoluminescence band of K 0.8 Na 0.2 BaY 0.95 (BO 3 ) 2 :0.05Ce 3+ decreased. However, the decreasing trend of FWHM became less obvious with the increasing concentration of Na + in the temperature dependent photoluminescence spectra of K 1− y Na y BaY 0.95 (BO 3 ) 2 :0.05Ce 3+ phosphors. [ABSTRACT FROM AUTHOR]