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A series of Ca3−xMx(PO4)2:Eu2+ (M = Sr, Ba) phosphors were prepared via a high-temperature solid-state reaction process. The X-ray diffraction and Rietveld refinements were used to verify the incorporations of Eu2+ into Ca3−xMx(PO4)2:Eu2+ (M = Sr, Ba). Upon excitation at 365 nm, the Ca3(PO4)2:Eu2+ phosphors exhibit a relatively narrow-band blue emission peaking at 415 nm attributed to the electric radiation transitions 4f65d1 → 4f7 of Eu2+. Moreover, the structural phase transformation and the unusual emission color variation of Ca3−xMx(PO4)2:Eu2+ (M = Sr, Ba) phosphors via the replacement of cationic M2+ (Sr2+, Ba2+) were reported. Upon excitation at the same wavelength of 365 nm, the emission peaks of Eu2+-doped Ca3−xSrx(PO4)2 phosphors red-shifted from 411 to 524 nm with increasing Sr/Ca ratio. The emission thermal stability of M3(PO4)2:Eu2+ (M = Ca, Sr, Ba) was comparatively characterized and the difference was related to the specific host structural features. The combination of host composition design may provide a novel strategy to obtain white light and tunable luminescence. [ABSTRACT FROM AUTHOR]

Abstract Ca 2 NaMg 2 V 3 O 12 (CNMV):Ln3+ (Dy3+, Sm3+) phosphors were successfully prepared by high temperature solid-state method. The effect of different Ln3+ concentrations on the luminescent properties of phosphor was investigated. General structure analysis system (GSAS) shown Ln3+ ions occupied Ca2+/Na+ sites. CNMV:Ln3+ (Dy3+, Sm3+) had broad excitation bands at 200–450 nm and broad emission bands at 400–700 nm. Under 365 nm excitation, CNMV:Dy3+ samples show two dominant emission peaks at around 480 nm and 575 nm, which is corresponding to 4F 9/2 -6H 15/2 and 4F 9/2 -6H 13/2 transitions of Dy3+, CNMV: Sm3+ samples show three emission peaks, which is corresponding to the 4G 5/2 -6H J/2 (J = 5,7,9) transitions of Sm3+. The energy transfer (ET) mechanism could be judged as an electric multipole interaction with their quenching concentration and critical distance. ET efficiency (ETE), lifetime, quantum efficiency (QE), color coordinates and good thermal stability were reported. Emitting-color tended to near white light when adjusting Ln3+ concentration. Highlights • The emitting-color of CNMV:Ln3+ was tunable by adjusting Ln3+ content. • There is energy transfer of VO 4 3−→Ln3+. • CNMV:Ln3+ phosphors show good thermal stability. [ABSTRACT FROM AUTHOR]

Y3−yAl5−xGaxO12:Ce3+y phosphors were prepared by high temperature solid state reaction method. The crystal structures, the influence of Ga3+ concentration on the photoluminescence (PL), cathodoluminescence, thermal stability and morphology of the phosphors were studied in detail. The results indicated that diffraction angle of the samples decreased gradually with the increase of Ga3+ ions content in XRD pattern. The emission peak of the spectra show a progressive blue-shift, the intensity increased first and then decreased and the optimal Ga3+ concentration in Y2.94Al5−xGaxO12:Ce3+0.06 phosphors is x = 0.75. The critical concentration of Ce3+ in YAGG:Ce3+ phosphors is affected with the ratio of Ga3+ to Al3+ and the Y2.9Al4.25Ga0.75O12:Ce3+0.1 phosphor showed the best performance on PL. However, the optimum concentration of Y3−yAl5−xGaxO12:Ce3+y phosphors is x = 1.5 and y = 0.04 when they were excited by cathode ray. [ABSTRACT FROM AUTHOR]

Rare earth doped up-conversion luminescent materials have been extensively studied for ratio optical thermometry. Compared with commonly used fluorides, oxides have low up-conversion luminous efficiencies but good thermal stability and are more suitable for high temperature environments. In this paper, a series of CaGdAl 3 O 7 : x% Er3+, y% Yb3+, z% Lu3+ phosphors were successfully prepared by high temperature solid-state reaction. Upon 980 nm laser excitation, the optimal CaGdAl 3 O 7 : 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows bright characteristic emission peaks of Er3+. CaGdAl 3 O 7 : 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows good temperature sensing performance from 303 K to 503 K. The absolute sensitivity reaches the maximum value at 428 K (S a = 0.292 % K−1). The maximum relative sensitivity is 0.917 % K−1 at 303 K. Moreover, CaGdAl 3 O 7 : 5 % Er3+, 35 % Yb3+, 1.5 % Lu3+ shows superior repeatability and reversibility. The results suggest that it is potential candidates as temperature sensors. • The up-conversion luminescence performance of CaGdAl 3 O 7 : Er3+, Yb3+ was successfully improved by introducing Lu3+. • The enhancement might be related to the local crystal field distortion caused by Lu3+ substitution. • The sample has excellent temperature sensing characteristics and the maximum relative sensitivity is 0.917 % K−1. [ABSTRACT FROM AUTHOR]

Using ammonia as a precipitation agent, (Y,Gd) 2 O 3 :Tb3+ x ,Dy3+ y ,Tm3+ z phosphors were synthesized by the co-precipitation method. In order to improve the luminescence performance of the luminescent center Tb3+, Tb3+-Dy3+ co-doping and Tb3+-Dy3+-Tm3+ tri-doping were successively carried out, and the optimal component formulations were determined by the controlled variable method (x = 0.03, y = 0.005, z = 0.001). XRD results showed that the sample has a cubic phase Y 2 O 3 structure with good crystalline properties. SEM results revealed that the samples have a unique micro morphology of small ball aggregation. The effects of doping concentration of Dy3+ and Tm3+ on the luminescence properties of Tb3+ were systematically investigated. The energy transfer mechanism among the three ions of Tb3+-Dy3+-Tm3+ was demonstrated by photoluminescence spectroscopy, and the main interaction modes between ions were elucidated. In addition, the matrix lattice environment can change the thermal stability properties of phosphors. In this paper, the temperature characteristics of Y 2 O 3 :Tb3+,Dy3+,Tm3+ phosphors are expected to be changed by microtuning the Y 2 O 3 matrix lattice with the introduction of Gd3+. The fluorescence intensity ratio (FIR) and thermal sensitivity indicated that Gd3+ has good temperature sensitivity, and its introduction can effectively improve the temperature sensing performance of the phosphors, which has a wide range of applications in optical temperature measurement sensors. [Display omitted] In this paper, Y 2 O 3 :Tb3+ x ,Dy3+ y ,Tm3+ z phosphor was synthesized by co-precipitation method. The specific research is as follows: • To improve the luminescence intensity of Tb3+ as the experimental index, the optimal component formulations of the sample was determined by the controlled variable method: x = 0.03, y = 0.005, z = 0.001. • The energy transfer relationship between Tb3+-Dy3+-Tm3+ ions in a Y 2 O 3 matrix was explored. • The optical temperature sensing performance of Y 2 O 3 :Tb3+,Dy3+,Tm3+ phosphors was investigated before and after the introduction of Gd3+. [ABSTRACT FROM AUTHOR]

LiAl 4 O 6 F (LAOF): Mn4+, Na+, Ga3+ red fluorescent materials were prepared by high temperature solid phase method. The properties of LAOF: Mn4+, Na+, Ga3+ phosphors were characterized by X-ray diffraction (XRD), photoluminescence (PL) spectra, variable temperature spectroscopy, scanning electron microscopy (SEM) and other tests. Under the excitation of 450 nm light, an intense red emission peak was observed around 662 nm, corresponding to the 2E g →4A 2g transition of Mn4+. Compared with Mn4+ single doping, the introduction of Na+, Ga3+ greatly improves the luminescence intensity of LAOF. The photoluminescence quantum yield of the optimal LAOF: 0.2%Mn4+, 0.2%Na+, 3%Ga3+ phosphor was measured to be 41.6%. The prepared sample have excellent thermal and water stability. Meanwhile, the w-LED device with a beneficial luminescence efficiency (LE = 331.7 lm W−1), exhibited good CRI and CCT values. These results indicate that LAOF: Mn4+, Na+, Ga3+ phosphors have potential application prospects as a red component in the field of lighting display. • Under the same excitation, the luminous intensity of LiAl 4 O 6 F: Mn4+, Na+, Ga3+ is 150% of LiAl 4 O 6 F: Mn4+. • The luminescence intensity of LiAl 4 O 6 F: 0.2%Mn4+, 0.2%Na+, 3%Ga3+ phosphor was maintained at 72% of the room temperature at 150 °C. • The luminescence intensity of LAOF: 0.2%Mn4+, 0.2%Na+, 3%Ga3+ phosphor was 60.92% of the initial one after 5 h of immersion. • LAOF: 0.2%Mn4+, 0.2%Na+, 3%Ga3+ phosphor was packaged into device can achieve a high luminous efficiency of 331.7 lm W−1. [ABSTRACT FROM AUTHOR]

• LLT: xTb3+, yEu3+ phosphors with garnet-type structure were prepared for the first time by solid-state reaction route. • The emitting-color was tunable designing ratio of Tb3+/Eu3+. • The introduction of Eu3+ significantly improves thermal stability, Tb3+ does the opposite. The thermal quenching behavior can be optimized by adjusting the dopant content. • The mechanism of Tb3+→Eu3+ energy transfer was investigated. In order to promote the development of white light emitting diodes (WLEDs) with improved color reproduction, the challenge by discovering novel photoluminescence color tuning phosphors via energy transfer (ET) is essential. However, the mechanism of energy transfer among dopants and its effect on ET efficiency have not been fully understood. Therefore, the photoluminescence color tuning in a variety of matrix structures based on energy transfer always needs to be discussed further. Herein, a series of wide-ranging color tunable Li 3 Lu 3 Te 2 O 12 phosphors doped with Tb3+/Eu3+ were synthesized by high-temperature solid-state reaction for the first time. The crystalline structure, morphology and chemical composition of as-prepared phosphors were characterized. The excitation and emission spectra, fluorescence decay curve, and the relationship among emission intensity, doping concentration of dopants and CIE coordinates were investigated in detail. The results indicate that photoluminescence color tuning from green to red was realized by designing the Tb3+→Eu3+ energy transfer in Li 3 Lu 3 Te 2 O 12 :Tb3+, Eu3+ phosphors. The approximation theory of Reisfeld and the electric multipole interaction theory of Dexter were used to analyze the ET mechanism, which reveals that the dipole-dipole and dipole-quadrupole interaction is responsible for the ET process of Tb3+→Tb3+ and Tb3+→Eu3+. In addition, the thermal stability of the as-prepared phosphors was also revealed. Unforgettably, the samples with reasonable design ratio of Tb3+/Eu3+ exhibits a wider color tuning range, excellent luminescence intensity under n-UV excitation and outstanding thermal stability comparable to commercial Y 2 O 3 :Eu3+ phosphor after surface treatment, whose emission intensity at 150 °C exceeds 70% of the initial value. In addition, a prototype WLED device was fabricated with representative phosphor and commercial blue phosphor BaMgAl 10 O 17 : Eu2+ (BAM: Eu2+), which emitted warm-white light with great color rendering index (CRI) of 84.8, softer correlated color temperature (CCT) of 3989 K and the chromaticity coordinates of (0.3647,0.3178). All the results suggest that Li 3 Lu 3 Te 2 O 12 :Tb3+, Eu3+ phosphors can be conducted as potential alternative for near ultraviolet (n-UV) pumped phosphor-converted white light-emitting diodes (pc-WLEDs). [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 Y 2.94-x Lu x Al 4 GaO 12 : 0.06Ce3+ phosphors were prepared by the conventional solid-state reaction method. It was confirmed that the phosphors exhibit cubic garnet crystal structures by XRD and Rietveld refinements. The phosphors show an intense broad emission band from 475 nm to 650 nm, which attributed to the 5d→4f transitions of the Ce3+ ions under the excitation of 450 nm. Simultaneously, obvious blue shift is observed from 518 nm to 497 nm with increasing Lu3+ concentrations from 0 to 2.94. With the increase of Lu3+ concentrations the emission intensity increases and reaches to the maximum for x = 2.5. By optimizing Lu3+ concentration, the quantum efficiency up to 89.8% is obtained. The emission intensity at 453 K is up to 92% of that at room-temperature indicating a weak thermal quenching and a superior thermal stability. These results indicate that the phosphor can be used in blue LED-Chip based white LEDs in the future. [ABSTRACT FROM AUTHOR]

The development of phosphors with high quantum efficiency and excellent thermal stability remains a challenging task for phosphor-converted white light-emitting diodes (w-LEDs). In this work, trisilicate-structured BaLu 2 Si 3 O 10 : Dy3+/Eu3+ (BLSO: Dy3+/Eu3+) series phosphors with stable performance were synthesized by high-temperature solid-phase reaction method. The results show that the Dy3+ monodoped trisilicate phosphor lacks a red component and exhibits cool white light properties, so Eu3+ ions are introduced into the matrix to compensate for the lack of the orange-red emission region. A detailed investigation of the photoluminescence properties of the double-doped phosphor light shows that Eu3+ ions can be well sensitized by Dy3+ under near-UV excitation at 350 nm. According to the Dexter's energy transfer equation and the Inokuti-Hirayama model, the energy transfer mechanism from Dy3+ to Eu3+ ions was confirmed as the electric dipole-quadrupole interaction, and the C DA value of the interaction parameter for the sample with Eu3+= 0.1 confirmed was 3.128 × 10−54 cm6 s−1, and the energy transmission efficiency could reach 70.09%. By controlling the wavelength of the excitation light and the Eu3+ ion concentration, the CIE coordinates of BLSO can be color adjusted in the white-yellow-orange-red region. The composition-optimized BLSO: Dy3+, Eu3+ phosphor has a CCT of 5622 K. The luminescence intensity of BLSO: 0.04Dy3+, 0.1Eu3+ at 423 K can be maintained at 81.15% of the luminescence intensity at 303 K, which is a satisfactory shows thermal fluorescence stability. From the obtained results, the prepared BLSO: Dy3+/Eu3+ phosphor can be proven as a potential color-tunable luminescent material for w-LEDs. • BaLu 2 Si 3 O 10 : Dy3+, Eu3+ phosphors with weak thermal quenching were synthesized via the conventional solid-state reaction method. • The energy transfer mechanism was determined by Inokuti-Hirayama model and the ET microparameter C DA = 3.128 × 10−54 cm6s−1. • The CIE color coordinates of the BLSO: 0.04Dy3+, 0.3Eu3+ sample was (0.330, 0.320) and the color temperature ∼5622.8 K. • The emission intensity of the BLSO: 0.04Dy3+, 0.1Eu3+ phosphor at 423 K could still maintain 81.15% of that at room temperature. [ABSTRACT FROM AUTHOR]

Multi-component luminescence materials (Lu 0.09 Gd 0.91) 2 O 2 S: Er3+, Yb3+ with response wavelengths of 980 nm, 1064 nm, and 1550 nm were synthesized by the coprecipitation-high temperature solid-state reaction method. The optimum formula was obtained by the orthogonal experiment method. The effects of Lu3+ on crystal structure, fluorescence intensity, and temperature stability were systematically studied. The phase composition of the phosphors was analyzed by X-ray diffraction. With the increase of Lu3+ concentration, the fluorescence intensity first decreases, then increases slowly to a maximum, and finally decreases sharply. The sample exhibits characteristic emissions of red and green under three wavelengths of excitation. In addition, the up-conversion luminescence mechanisms excited at different wavelengths were discussed by means of the Intensity-Power test. Through a series of temperature spectra, it is found that the introduction of Lu3+ contributes to excellent temperature stability. Subsequently, the decay curve shows that the fluorescence lifetime of 554 nm increases first and then decreases with the increase of Lu3+ concentration, resulting from competition between γ and knr. This provides a useful idea for developing infrared detection materials with excellent temperature stability and luminescence properties. [Display omitted] • Gd 2 O 2 S: Er3+, Yb3+ phosphorse were prepared by the coprecipitation-high temperature solid-state reaction method. The composition of cations was optimized by the orthogonal experiments. • With the increase of Lu3+ concentration, the fluorescence intensity of the (Lu x Gd 1−x) 2 O 2 S: Er3+, Yb3+ phosphors first decreases, then increases slowly to a maximum, and finally decreases sharply. • With the increase of temperature, the total intensity of the (Lu 0.09 Gd 0.91) 2 O 2 S: Er3+, Yb3+ phosphors are higher than that of Gd 2 O 2 S: Er3+, Yb3+ phosphors. From 300 K to 400 K, the total intensity of the Gd 2 O 2 S: Er3+, Yb3+ phosphors changes irregularly. • With the increase of Lu3+ concentration, The lifetime of the (Lu x Gd 1−x) 2 O 2 S: Er3+, Yb3+ phosphors increases first and then decreases, which is similar to the observed trend of luminescence intensity. [ABSTRACT FROM AUTHOR]

Y 2 Mg 3 Ge 3 O 12 : RE3+ (RE ​= ​Tb, Eu, Tm) phosphors were prepared by solid phase method. XRD and EDS show that the samples were pure phases. The ET efficiency of Y 2 Mg 3 Ge 3 O 12 : Tb3+, Eu3+ can reach up to 96.63%, and the mechanism is d-d interaction. In Y 2 Mg3Ge 3 O 12 : Tb3+, Eu3+, Tm3+, the intensity of Tb3+ decreases with the increase of Eu3+ concentrations, and the intensity of Tm3+ is basically unchanged, the intensity of Eu3+ increased first and then decreased. Meanwhile, the ET efficiency can reach up to 77.53%. Moreover, the luminescence intensity at 423 ​K can still be maintained at 87–96.58% of that at the initial temperature. The value of CCT which shows a decreasing trend with increasing Eu3+ concentrations also indicates that warm white light can be obtained by triple doping of Tb3+-Eu3+-Tm3+. The above findings show that these samples are likely to be used in warm w-LEDs. Single-component Y 1.46-y Mg 3 Ge 3 O 12 : 0.5 ​Tb3+, 0.04 ​Tm3+, yEu3+ white phosphors with excellent thermal stability were prepared by high-temperature solid-phase method.In this paper, Y 1.46-y Mg 3 Ge 3 O 12 : 0.5 ​Tb3+, 0.04 ​Tm3+, yEu3+ garnet-type phosphors with near-UV excitation were successfully synthesized. The energy transfer efficiency reached 77.53%. Y 1.46-y Mg 3 Ge 3 O 12 : 0.5 ​Tb3+, 0.04 ​Tm3+, yEu3+ samples have good thermal stability. When the samples were heated to 423 ​K, the luminescence intensity could still reach more than 87% and 96% of the luminescence intensity at the initial temperature. [Display omitted] • Y 2 Mg 3 Ge 3 O 12 : Tb3+, Eu3+, Tm3+ phosphors were synthesized by high-temperature solid-phase method. • The intensity at 423K can still reach 87% of that at 303 K, indicating a good thermal stability. • The maximum energy transfer efficiency was 93.63% and 77.53%. [ABSTRACT FROM AUTHOR]

A series of Dy3+ activated Ba(YLu) 2 Si 3 O 10 samples were prepared by high temperature solid-phase method. The purity of the phase was determined and the structural changes were analyzed. Under excitation at 350 nm, the BaY 2 Si 3 O 10 : Dy3+ phosphor shows two stronger luminescence peaks at 486 nm and 572 nm and weaker emission peak at 668 nm. In addition, with the continuous replacement of Y3+ in the matrix by Lu3+ ions, the chromaticity coordinates of samples in the system can be adjusted from the cold white region to the warm white region, and the luminescence performance of phosphors can be effectively improved. It was observed that the thermal stability of the phosphor was gradually enhanced with Lu3+ concentration increases, and the emission intensity of the BaLu 2 Si 3 O 10 : 0.04Dy3+ phosphor at 453 K could still maintain 83.78% of that at room temperature, which was discussed in conjunction with the Debye temperature and the rigid structure model to provide a reference for the improvement of the thermal stability performance. In addition, the increase of the concentration of Lu3+ ions doping will shorten the lifetime of phosphors due to the non-radiative energy transfer caused by the shortening of the ion distance in the lattice. • Ba(YLu) 2 Si 3 O 10 : Dy3+ phosphors with weak thermal quenching were synthesized. • The emission intensity of phosphor increased by 23.23% with increasing Lu3+ content from 0 to 2. • The chromaticity coordinates of samples can be effectively adjusted from the cold white region to the warm white region. • The emission intensity of the BaLu 2 Si 3 O 10 : 0.04Dy3+ could still maintain 83.78%. [ABSTRACT FROM AUTHOR]

• Ca 2 P 2 O 7 : Dy3+, Eu3+ phosphors were synthesized via the hydrothermal synthesis. • With the increase of pH value, the morphology of samples changed from spindles, tetragonal particles to long rods. • The best luminescence property of the sample is prepared at pH of 4 and a calcination temperature of 1000 °C. • With the calcination temperature increases, the phosphor morphology changed from long rods to tetragonal particles. • The chromaticity coordinate of Ca 2 P 2 O 7 : 0.04Dy3+, 0.03Eu3+ phosphors was calculated to be (0.463, 0.340). The Ca 2 P 2 O 7 : Dy3+, Eu3+ phosphors were synthesized via hydrothermal method. The three-dimensional network structure of Ca 2 P 2 O 7 consisted of strong P-O covalent bond in [P 2 O 7 ] and weak coupling between [P 2 O 7 ] and Ca. The morphology was shown in detail by TEM and SEM images of precursors changed from spindles, tetragonal particles to long rods with the pH increased from 2 to 5. After sintering, the sample had the best luminescence property when pH was 4. The optimum sintering temperature was 1000 °C. The emission spectrum of Ca 2 P 2 O 7 : Dy3+ was composed of three emission peaks. Based on the optimized doping concentration of Dy3+ was 0.04 mol, the doping of Eu3+ ions increased the red emission of the samples and finally samples obtained warm white emitting. The concentration quenching mechanism in the energy transfer from Dy3+ to Eu3+ was caused by dipole-dipole interaction. Ca 2 P 2 O 7 : Dy3+, Eu3+ had excellent thermal stability. Thus, Ca 2 P 2 O 7 : Dy3+, Eu3+ phosphor which could emit warm white light has fantastic potential applications for UV excited LED. [ABSTRACT FROM AUTHOR]

A solid solution with double perovskite La 2-x-y Y x MgTiO 6 :yEu3+ system was prepared by high-temperature solid-phase method. The structure of the as-synthesized samples was obtained from XRD patterns and Rietveld refinement. Under the excitation of UV light at 396 nm, the samples appeared red at 616 nm. As the concentration of Eu3+ increases, the luminous intensity of La 2-y MgTiO 6 :yEu3+ phosphor gradually increases, and it shows an optimal luminous intensity where y = 0.20. Based on this, when x = 1.75, the optimum luminescence intensity of the sample is 154.1% and 131.4% of La 1·8 MgTiO 6 :0.2Eu3+ and Y 1·8 MgTiO 6 :0.2Eu3+, respectively. The thermal stability of La 1.8-x Y x MgTiO 6 :0.2Eu3+ was tested. compared with the sample with an initial temperature of 303 K, the luminescence intensity of the optimal sample decreased to 95.75% when the temperature reached 423 K. And the thermal stability of Y3+ doped phosphors increased 46.5% and 24.4% compared to the original La 1·8 MgTiO 6 :0.2Eu3+ and Y 1·8 MgTiO 6 :0.2Eu3+. The results indicate that it is a suitable candidate for lighting materials required by the modern market. • We have discovered a new La 2-x-y Y x MgTiO 6 :yEu3+ red phosphor, and prepared by high temperature solid phase method. • The emission intensity at 423 K can still reach 95.75% of 303 K, indicating a good thermal stability and practicality. • When x = 1.75, the luminescence properties are the best, and the intensity is 154% of LMT:0.2Eu3+ and 131% of YMT:0.2Eu3+. • The red lights demand of different plants at different growth stages can be met by adjusting the amount of phosphor. [ABSTRACT FROM AUTHOR]

A series of Y 2-x-y Mg 3 Ge 3 O 12 : xDy3+, yTb3+ samples were manufactured by high temperature solid phase method. XRD test and Rietveld refinement clarified the phase purity of the samples. When the excitation wavelength is 352 nm, the energy transfer efficiency is 57.74%, and q-q interaction is the main energy transfer mechanism of Dy3+-Tb3+ co-doped samples. In addition, we tested the thermal stability of Y 1.94 Mg 3 Ge 3 O 12 :0.05Dy3+, 0.01 Tb3+ sample, and found that its luminous intensity at 423 K could still reach 93.86% of that at 303 K. By changing the concentrations of Tb3+, the luminescent color of the samples could also be changed from blue-white light to yellow-green light. These results indicate that Y 2 Mg 3 Ge 3 O 12 co-doped with Dy3+ and Tb3+ is expected to be applied in the field of white light LEDs. • Y 2-x-y Mg 3 Ge 3 O 12 : xDy3+, yTb3+ phosphors with weak thermal quenching were synthesized by high-temperature solid-phase method. • The emission intensity at 423 K can reach 93.86% of that at room temperature, indicating a good thermal stability. • As the concentrations of Tb3+ increase, the energy transfer efficiency increases from 25.51% to 57.74%. [ABSTRACT FROM AUTHOR]

• Dy3+, Eu3+ co-doped NaBi(WO 4) 2 phosphors were successfully synthesized. • The structure and luminescence behaviors of obtained samples were studied in detail. • NaBi(WO 4) 2 : 0.08Dy3+, 0.1Eu3+ phosphor possesses excellent thermal stability. • The obtained phosphors are potentially applicable for NUV excited WLEDs. A series of Dy3+, Eu3+ co-doped NaBi(WO 4) 2 phosphors with excellent thermal stability were synthesized by the solid state method for the warm white light-emitting diodes. [Display omitted] A variety of Dy3+ single-doped and Dy3+, Eu3+ co-doped NaBi(WO 4) 2 phosphors were synthesized by the high temperature solid state method. The XRD patterns and Rietveld refinement measurement were operated to identify the crystalline phases. When the NaBi(WO 4) 2 : 0.08Dy3+, yEu3+ phosphors were excited by 352 nm light, the energy transfer efficiency can be reach to 72.576% and the type of energy transfer mechanism was dominated by the dipole-dipole interaction. The thermal stability of specific NaBi(WO 4) 2 : 0.08Dy3+, 0.1Eu3+ phosphor was tested and the PL emission intensity at 423 K drops to about 77.2% of that at 303 K, and the warm white light can be obtained after varying the Eu3+ ion concentration. Aforementioned results manifest that these as-prepared samples are expected to be the potential single-phase phosphors used in the areas of solid state lighting. [ABSTRACT FROM AUTHOR]

A battery of Dy3+ single-doped and Dy3+/Eu3+ co-doped Y 2 Mg 3 Ge 3 O 12 phosphors were manufactured by high-temperature solid-phase method. The XRD patterns were tested and Rietveld refined. When the samples were excited by 352 ​nm near ultraviolet light, the energy transfer efficiency can reach 83.2%, and the energy transfer mechanism is electric dipole-electric dipole interaction. The thermal stability of Y 1.75 Mg 3 Ge 3 O 12 :0.05Dy3+, 0.2Eu3+ was tested. When the temperature reached 150 ​°C, its luminous intensity droped to 92.4% of the initial temperature (30 ​°C). By changing the concentrations of Eu3+, white light with red light can be obtained. The above results indicate that these samples are expected to become candidate materials in the domain of solid-state lighting. In this paper, a near-ultraviolet excited garnet type Y 2 Mg 3 Ge 3 O 12 : Dy3+/Eu3+ phosphors were synthesized successfully. The energy transfer efficiency reaches 83.2%. The Y 1.95-y Mg 3 Ge 3 O 12 : 0.05Dy3+, yEu3+ samples have excellent thermal stability. When the sample was heated to 150 ​°C, the luminous intensity can still reach 92.4% of the luminous intensity at the initial temperature. [Display omitted] • Y 1.95-y Mg 3 Ge 3 O 12 :0.05Dy3+, yEu3+ were synthesized by high temperature solid phase method. • For Y 1.95-y Mg 3 Ge 3 O 12 : 0.05Dy3+, yEu3+ phosphors, the energy transfer efficiency is calculated to be 83.2%. • The emission intensity can still reach 92.4% at 423K of that at room temperature. [ABSTRACT FROM AUTHOR]

In this paper, Dy3+ doped and Dy3+/Eu3+ co-doped Ca 3 (PO 4) 2 phosphors were prepared through hydrothermal synthesis method. pH value in the initial reaction solution had an important effect on the determination of phosphate morphology. With the increase of pH value, the morphology of samples changed from nanorods to nano-spherical grains. The Ca 3 (PO 4) 2 : Dy3+ phosphors could be efficiently excited by 350 nm and its concentration quenching occurred when the concentration of Dy3+ was beyond 0.03 due to dipole-dipole interaction. With increasing content of Eu3+ in Ca 3 (PO 4) 2 : Dy3+, Eu3+ phosphors, the emission intensity of Dy3+ decreased, and that of Eu3+ increased to maximum when Eu3+ concentration was 0.08, and then decreased. The energy transfer (ET) from Dy3+ to Eu3+ in Ca 3 (PO 4) 2 host was expressed through the quadrupole-quadrupole mechanism, and the maximum of ET efficiency was 82.40%. When Ca 3 (PO 4) 2 : Dy3+, Eu3+ phosphors excited by 362 nm, the CIE coordinates ranged from (0.295, 0.330) to (0.367, 0.326). Moreover, the samples had good thermal stability. The emission intensity of the sample at 460 K decreased to 85.67% of that at 300 K. Our results display that Ca 3 (PO 4) 2 : Dy3+/Eu3+ phosphors are potential candidate for applications in the near-UV pumped warm white LEDs. • Dy3+, Eu3+ doped Ca 3 (PO 4) 2 warm-white-emitting phosphors were synthesized via the hydrothermal synthesis method. • The optimal doping concentration of Eu3+ ions was found to be 8 mol%. • With the increase of pH value, the morphology of samples changed from nanorods to nano-spherical grains. • The energy transfer efficiency of the phosphor was 82.40%. • The phosphor possessed excellent thermal stability. The emission intensity at 460 K decreased to 85.67% of that at 300 K. [ABSTRACT FROM AUTHOR]

In this work, NaBi(WO 4) 2 :Eu3+ red phosphors were synthesized by high temperature solid-state method. The XRD and Rietveld refinement were used to analyze the crystal structure, and the morphology was investigated by the SEM. Upon excitation with 395 nm, these phosphors exhibited intense red emission at 615 nm attributing to the 5D 0 →7F 2 transition of Eu3+ ions. The optimal doping concentration of Eu3+ ions in NaBi(WO 4) 2 :xEu3+ phosphors was x = 0.8, and the electric dipole-dipole interaction dominates the concentration quenching mechanism. The Judd–Ofelt intensity parameters (Ω 2 and Ω 4) were determined to confirm the site asymmetry of Eu3+ ions in NaBi(WO 4) 2 host. Furthermore, the NaBi(WO 4) 2 :0.8Eu3+ phosphor also possesses excellent thermal stability with the PL emission intensity still keep up about 88.2% at 423 K comparing with that at 303 K, meanwhile, the internal quantum efficiency (IQE) of it was measured to be 83.6%. The CIE chromaticity coordinate of NaBi(WO 4) 2 :0.8Eu3+ sample was (0.656, 0.343), and the color purity of it was calculated to be as high as 95.8%. Based on the results above, the NaBi(WO 4) 2 :Eu3+ phosphors are promising red components, which can be utilized in the applications of near-ultraviolet (NUV) pumped WLEDs. • Eu3+ doped NaBi(WO 4) 2 red-emitting phosphors were developed. • The optimal doping concentration of Eu3+ ions was found to be 80 mol%. • The NaBi(WO 4) 2 :0.8Eu3+ phosphor had good color purity of 95.8%. • The internal quantum efficiency of the phosphor was 83.6%. • The red phosphor possessed excellent thermal stability. [ABSTRACT FROM AUTHOR]

SrB 2 Si 2 O 8 : Tb3+ and SrB 2 Si 2 O 8 : Ce3+, Tb3+ phosphors were synthesized through conventional high temperature solid state reaction method. Under near ultraviolet (NUV) excitation of 377 nm, the emission peaks of the SrB 2 Si 2 O 8 : Tb3+ green phosphor located at 489, 544, 585 and 623 nm corresponding to Tb3+ ions energy level transition of 5D 4 excitation state to 7F 6 , 7F 5 , 7F 4 and 7F 3 ground states, respectively. The optimal concentration of Tb3+ ions is 11at.%, and the concentration quenching mechanism can be interpreted by the dipole-quadrupole interaction of Tb3+ ions. For the Sr 1-x B 2 Si 2 O 8 : Ce3+, xTb3+ phosphors, the maximum luminescence intensity is 21 times higher than that of the single doped Tb3+, which originates from the energy transfer of Ce3+ to Tb3+ ions. The energy transfer efficiency is calculated to be 79.7%, which is caused by the dipole-dipole resonant type. The CIE coordinates of SrB 2 Si 2 O 8 : Ce3+, Tb3+ phosphors change from blue (0.167, 0.071) to green (0.241, 0.546). When the temperature reaches 210 °C, the luminescence intensity reaches 72.20% of the initial value, indicating that the materials have good thermal stability. The above consequences demonstrate that the SrB 2 Si 2 O 8 : Ce3+, Tb3+ phosphors can be used as a candidate for a promising green luminescent phosphor in ultraviolet excited W-LEDs. Energy level diagram of energy transfer in the SrB 2 Si 2 O 8 : Ce3+, Tb3+ phosphors; CIE diagram of Ce3+/Tb3+ doped SrB 2 Si 2 O 8 phosphors. Image 1 • Ce3+, Tb3+ co-doped energy transfer was first proposed in SrB 2 Si 2 O 8 phosphor. • The energy transfer efficiency of Ce3+ to Tb3+ is as high as 79.7%. • The luminescence intensity of Ce3+, Tb3+ co-doped is 21 times higher than that of single-doped Tb3+. • The energy transfer from Ce3+ to Tb3+ is caused by the resonance of the dipole-dipole. • Ce3+, Tb3+ co-doped SrB 2 Si 2 O 8 phosphors have potential applications in ultraviolet excited W-LEDs. [ABSTRACT FROM AUTHOR]