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Enhancing the moisture resistance of Mn4+-doped fluoride phosphors is crucial for solid-state lighting (SSL) and liquid crystal display (LCD). Herein, the deteriorated K2AF6:Mn4+ (A = Ti, Si) phosphors were restored with Na2SO3 alkaline reductant, and optimal treatment conditions were systematically determined. The kinetic process for luminescence degradation and restoration, as well as the corresponding reparation mechanism were investigated in detail. These results showed that SO32− anion can reduce Mn4+ to Mn2+, rapidly remove the dark-brown layer of the degradation product, and restore the luminescence intensity of K2AF6:Mn4+ to more than 95%. Therefore, the restored K2TiF6: Mn4+ and K2SiF6: Mn4+ samples exhibit excellent moisture resistance, maintaining to be 66 and 76% of the initial intensity after immersing in deionized water for 300 min. Furthermore, fabricated white light-emitting device using the restored K2TiF6: Mn4+ phosphor also possess color rendering index of 94.2 and correlated color temperature of 3270 K. Our results provide a feasible strategy to significantly improve the moisture resistance of fluoride phosphors, demonstrating a great promise in phosphor-converted white-LED toward lighting and display field. [ABSTRACT FROM AUTHOR]

Y1.94MAl4SiO12:0.06Ce3+ (M = Ba, Sr, Ca, Mg) phosphors were successfully prepared through a classic solid‐state reaction method. The crystal structures, photoluminescence spectra, quantum yields, and thermal stabilities of the phosphors were investigated in detail. The results indicate that all Y1.94MAl4SiO12:0.06Ce3+ phosphors maintain the crystal structure of garnets. The emission peaks of Y1.94MAl4SiO12:0.06Ce3+ (M = Ba, Sr, Ca, Mg) phosphors are located at 537, 538, 554, and 565 nm, respectively. A red‐shift trend of emission peak is observed with decreasing M radius, which can be ascribed to the increase in the crystal‐field splitting in the Ce3+ 5d level owing to the co‐doping of M2+−Si4+. Under 460 nm excitation, the luminescence quantum yields and thermal stabilities of the Y1.94MAl4SiO12:0.06Ce3+ phosphors decreased with the decrease of M radius. The IQE of the Y1.94BaAl4SiO12:0.06Ce3+ phosphor is 92.89%, and the resistance to thermal quenching is improved to be 93.32% at 150°C. In addition, the color shifts of Y1.94MAl4SiO12: 0.06Ce3+ phosphors with increasing temperature are all tiny, which also demonstrates good resistance to thermal quenching of luminescence. The linear shrinkage of Y1.94MAl4SiO12:0.06Ce3+ phosphors is significantly improved compared with that of YAG: Ce3+, which is expected to generate Y1.94MAl4SiO12:0.06Ce3+ transparent/translucent ceramics and fabricate high‐powder w‐LEDs for high‐quality solid‐state lighting in the future. [ABSTRACT FROM AUTHOR]

Current white light emitting diodes (WLEDs) have poor thermal stability and lack red‐light, which restrict their applications in high‐power and high‐color‐rendering‐index solid‐state lighting. YAG glass‐ceramics provide an efficient way to resolve these problems. Herein, novel YAG‐embedded calcium bismuth borate glass‐ceramics (YAG‐GCs) with Eu3+ doping were prepared using a rapid melt quenching technique. The precursor glass exhibits superior YAG refractive index matching and high transmittance. Differential scanning calorimeter simulations verify YAG particles react with the precursor glass. The degree of YAG erosion is slight but monotonously increases with the co‐sintering temperature from 640 to 700°C. The erosion products probably contain YAB (Al3Y(BO3)4), Al3Eu(BO3)4, Bi24B2O39, and Ca12Al14O33 phases, and the Bi ion valence state is maintained during the reaction process. The energy transfer from Ce3+ to Eu3+ is suppressed. The YAG‐GC PL intensities monotonously increase as the co‐sintering temperature decrease from 640 to 700°C and the YAG content increase from 2.5 to 7 wt.%. The optical parameters of a WLEDs packed by YAG‐GCs and blue chips are a luminous efficiency of 105.3 lm/W, correlated color temperature of 3940 K and color rendering index of 70.1. The as‐prepared YAG‐GCs are promising candidates for high‐power, warm WLEDs due to their superior thermal stability, high quantum efficiency, and low cost. [ABSTRACT FROM AUTHOR]

A series of Er3+, Tm3+, Yb3+ co-doped or tri-doped SrLu2O4 phosphors were synthesized by a high-temperature solid-state reaction method. The crystal structure was characterized by X-ray diffraction technique and further validated by Rietveld refinement. The chemical composition and elemental distribution of tri-doped sample were determined by the energy-dispersive spectrometry. It is worthwhile to note that the upconversion (UC) luminescence of as-prepared samples could be precisely controlled by adjusting the Yb3+ doping concentration and the excitation pump power. A bright UC white light in Er3+/Tm3+/Yb3+ tri-doped SrLu2O4 samples was observed by controlling the intensities of red, green and blue emissions. Under various pump powers in the range of 290-810 mW, the color coordinates could be effectively tuned in a quite broad white region. Particularly, the color coordinate of optimal sample under 630 mW at 980-nm excitation is (0.3336, 0.3244), which is very close to the standard white-light illumination (0.333, 0.333) and the corresponding correlated color temperature is 5442 K. Based on the UC emission spectra and luminescence decay curves, the energy transfer (ET) mechanisms involved in the different UC processes were proposed in detail. The results imply that ET processes of Yb3+ → Er3+, Yb3+ → Tm3+ and Tm3+ → Er3+ worked simultaneously in tri-doped system and produced white UC emissions by means of two- or three-photon processes. The Er3+/Tm3+/Yb3+ tri-doped SrLu2O4 phosphor can be a potential candidate for white UC material in displays, backlights and white-light sources. [ABSTRACT FROM AUTHOR]

The poor thermal stability of current commercial white light emitting diodes (WLED) fabricated using a blue chip, a yellow YAG:Ce 3+ phosphor (YAG) and resins, restricts their application in fields where long service time and high power lighting systems are required. Incorporating YAG into glass offers a possible way to resolve the problem by removing the organic resins in LED encapsulation. In the present study, YAG glass-ceramics with bismuth borate glass matrices were prepared using a rapid melt quenching technique. The YAG erosion mechanism was investigated for the first time in various glass matrix compositions at different co-sintering temperatures. The results demonstrate that neither B 2 O 3 nor Bi 2 O 3 individually erodes YAG particles, but the mixtures of B 2 O 3 and Bi 2 O 3 binary glass systems react with YAG and dissolve it almost completely or generate YAl 3 (BO 3 ) 4 (abbreviated as YAB), and they even erode as-produced YAB again under certain conditions. The production of YAB particles increases with the increase of the n Bi /n B ratio at a lower temperature (680 °C), while it first increases and then decreases at a higher temperature (800 °C). The maximum production of YAB can be obtained at the co-sintering temperature of 680 °C with an n Bi /n B ratio of 55:45 or at 760 °C with an n Bi /n B ratio of 35:65. The intermediate Bi 4 B 2 O 9 phase is found during the transformation of YAG into YAB. A simple but efficient approach is proposed to prevent YAG erosion and increase the luminous properties of YAG glass ceramics to a great extent by simply adding Ca 2+ into bismuth borate glass matrices. The degree of YAG erosion decreases with increasing Ca 2+ concentration until an impurity phase appears when the Ca 2+ concentration exceeds 20 mol%. The combination of good white light emission and suitable quantum efficiency as well as higher thermal stability makes the as-prepared YAG glass-ceramics equipped with a blue chip a possible alternative to commercial WLED. [ABSTRACT FROM AUTHOR]

A series of novel Er 3+ doped and Er 3+ /Yb 3+ co-doped Ba 3 Lu 4 O 9 phosphors were synthesized by a simple high-temperature solid-state reaction method. The crystal structure and morphology of the samples were identified by XRD and SEM analysis. Under 980 nm laser diode excitation, the green (at 537 nm and 560 nm) and red (at 660 nm) UC emission were observed, which could be attributed to the ( 2 H 11/2 , 4 S 3/2 )→ 4 I 15/2 and 4 F 9/2 → 4 I 15/2 transitions, respectively. The UC luminescence can be finely tuned from green to dark-yellow light to some extent by increasing Yb 3+ doping concentration. The sintering temperature and doping concentration of Ba 3 Lu 4- x - y O 9 : x Er 3+ , y Yb 3+ were optimized to x = 0.1 and y = 0.6 at 1550 °C. The emission intensity ratio of Green/Red keeps declining monotonically with increasing Er 3+ or Yb 3+ concentration, which is due to the cross-relaxation effect and cooperative energy transfer between the two neighboring Er 3+ ions-as well as back energy transfer from Er 3+ to Yb 3+ ions. Based on the pump-power dependence and UC luminescence decay curves, the energy level diagram and the possible energy transfer mechanism of Er 3+ doped as well as Er 3+ /Yb 3+ co-doped system were investigated in detail. In addition, according to the energy gap law, the possibilities of non-radiative transition between parts of energy levels of Er 3+ ions were calculated. [ABSTRACT FROM AUTHOR]

Eu-doped BaAlO red phosphors were synthesized by high-temperature solid-state reaction. The crystal structure, morphology and luminescence properties were investigated by XRD, TEM and photoluminescence spectroscopy. The effect of calcination temperature, Eu concentration as well as charge compensators on the luminescence properties was also investigated. Characteristic orange-red emission at 589 nm was detected under 394 nm excitation. The best performance could be derived for the sample calcined at 1450 °C. With the increase of Eu concentration, the emission intensities increased gradually up to the Eu concentration of 12 %. The emission intensities could be enhanced with Li, Na and K introduced as charge compensators. The results showed that BaAlO:Eu phosphors with charge compensator had potential application in the fields of near-UV-excited WLEDs. [ABSTRACT FROM AUTHOR]

Full-spectrum lighting has become the development direction for human-centric illumination. However, the reabsorption effect caused by cyan, green and yellow multiple-phosphor packaging leads to low luminous efficiency. In this work, a broadband cyan-green phosphor is proposed to replace the cyan and yellow phosphors for highly efficient and thermally robust full-spectrum WLEDs. A new family of oxyfluoride garnet phosphors Lu 2 QMg 2 Al 3 O 9 F 3 : Ce3+ (Q = Ca, Sr, Ba) has been developed by incorporating F- into the classic LuAG: Ce3+ green phosphor. The excess charge was compensated by substituting trivalent Lu3+ and Al3+ with divalent alkaline earth element. The low covalency and phonon energy of fluorine-containing system endow these serial phosphors with efficient and thermally stable blue-shifted emission. The representative Lu 2 SrMg 2 Al 3 O 9 F 3 : Ce3+ exhibits a broadband cyan-green emission peaked at 513 nm with a 105 nm FWHM. Furthermore, outstanding quantum efficiency (88.4%) and thermal stability (94.3% @ 423 K) were achieved. This oxyfluoride phosphor was packaged with red phosphor without cyan phosphor on a blue chip. The obtained WLEDs show an excellent color rendering index (R a = 96.8) with luminous efficiency (LE = 106 lm/W). This research might pave a promising avenue for the development of next-generation full-spectrum lighting. • A new family of oxyfluoride garnet cyan-green phosphors was obtained. • The F- incorporation endows the phosphors with efficient and thermally stable blue-shifted emission. • The Lu 2 SrMg 2 Al 3 O 9 F 3 : Ce3+ exhibits a 513 nm centered emission with a 105 nm FWHM. • Ra=96.8 and LE=106 lm/W were achieved by replacing the cyan and yellow phosphor. [ABSTRACT FROM AUTHOR]

Compared with oxide-based NIR phosphors, fluoride phosphors have received great attention recently due to their good thermal resistance and high photoelectric efficiency. In this work, novel LiBAlF 6 :Cr3+ (B = Ca, Sr) with low phonon energy and relatively weak electron-phonon coupling were synthesized through a facile hydrothermal approach. Benefiting from low Dq/B, an ultra-broad NIR emission extending from 650 nm to 1100 nm can be achieved in these phosphors under excitation of blue light. Among them, LiSrAlF 6 :Cr3+ presents a FWHM of 155 nm. At 423 K, LiCaAl 0.4 F 6 : 0.6Cr3+ and LiSrAl 0.4 F 6 : 0.6Cr3+ maintain 66.63% and 55.47% of their initial intensities, respectively. Better thermal stability of LiCaAlF 6 : Cr3+ could be attributed to the broad band gap and weak electron-phonon coupling effect. Photoelectric conversion efficiencies of 5.002% and 5.468% at 300 mA could be obtained for NIR pc-LEDs packaged with LiCaAl 0.4 F 6 : 0.6Cr3+ and LiSrAl 0.4 F 6 : 0.6Cr3+, respectively. A slightly internal bruise inside apple and water level behind trademark in bottle could be clearly detected, revealing that LiBAlF 6 :Cr3+ (B = Ca, Sr) phosphors have great application potential in infrared inspection. [ABSTRACT FROM AUTHOR]

Eu2+-activated BaSi 2 O 2 N 2 oxonitridosilicate phosphor is an efficient cyan compensator to improve the color rendering index of WLEDs for full-spectrum lighting. However, the low luminescent efficiency and poor thermal stability of this type of phosphor severely restrict its practical industry applications. Herein, SiC was proposed into the preparation process of BaSi 2 O 2 N 2 to enhance the luminescence and thermal stability. Due to the very small amount of SiC addition, the samples of BaSi 2 O 2 N 2-4x/3 C x :Eu2+ maintain the orthorhombic crystal structure of BaSi 2 O 2 N 2 :Eu2+, but the unit cell volumes and particle sizes become larger. The luminescent intensity reaches the maximum when x = 0.075 and the absorption efficiency and internal quantum efficiency are 67.59% and 58.26%, which are increased by 5.34% and 14.66% relative to the SiC-free sample, respectively. The bandgap and lifetime of Ba 0.97 Si 2 O 2 N 1.9 C 0.075 :0.03Eu2+ are calculated to be 2.06 eV and 407.91 ns, respectively. The sample of Ba 0.97 Si 2 O 2 N 1.9 C 0.075 :0.03Eu2+ possesses a higher activation energy of 0.383 eV and exhibits a little loss of 13.3% of luminescence intensity at 423 K, which is improved by 11.4% relative to the SiC-free sample. Higher structural stiffness derived from the partially replacement of Si−N bonds by Si-C is supposed as the main reason of the higher thermal stability. The luminescence of Ba 0.97 Si 2 O 2 N 1.9 C 0.075 :0.03Eu2+ degrades only by 4.64% in five thermal cycles, which mainly thanks to the improved antioxidant of Eu2+. The Ba 0.97 Si 2 O 2 N 1.9 C 0.075 :0.03Eu2+ sample demonstrates an excellent color stability with a tiny chromaticity shift of ~28.19 × 10-3 ranging from 298 to 423 K. A WLED with the cyan-emitting Ba 0.97 Si 2 O 2 N 1.9 C 0.075 :0.03Eu2+ exhibits a full spectrum with CRI of 95.1. [ABSTRACT FROM AUTHOR]

Research on near-infrared (NIR) emission of Tm3+ and Yb3+ co-doped upconversion (UC) materials has accepted many interests owing to delightful features for frontier applications. In this work, we focus on the preparation of pure NIR emission and the improvement of absolute sensitivity (S A) on temperature in Tm3+ and Yb3+ co-doped novel double perovskite Gd 2 ZnTiO 6 (GZT) phosphors. Upon 980 nm excitation, these phosphors perform dramatical NIR emissions, and the integral intensity percentage of NIR emission versus total visible emissions reaches up to 99.88%. A high S A value with 1.7351 K−1 at 473 K for the I 801 /I 650 is obtained via introducing excellent NIR emission. Besides, the S A value of non-thermally coupled levels is higher than that of thermally coupled levels. These results suggest that this kind of UC material may be a candidate for NIR imaging and temperature detection applications. Image 1 High sensitivity based on non-thermally coupled levels is received via utilizing intense NIR emission in Tm3+ and Yb3+ co-doped double perovskite GZT phosphors. • Upconversion properties of Tm3+ and Yb3+ co-doped novel double perovskite Gd 2 ZnTiO 6 phosphors are investigated in detail. • Intense and nearly pure NIR emission with high integral intensity percentage that achieves 99.88% is obtained. • High S A with 1.7351 K−1 at 473 K for N-TCLs is received via utilizing intense near-infrared emission. [ABSTRACT FROM AUTHOR]

A series of novel green emitting γ -AlON: Mn2+, Mg2+ and γ -AlON: Mn2+, Mg2+, M (M = Li+, Na+, K+, Si4+) phosphors were fabricated with the gas-pressure sintering reaction process. The phase structure, morphology and photoluminescence properties of the phosphors were characterized via X-ray powder diffraction, scanning electron microscopy, and photoluminescence spectroscopy. Meanwhile, the charge compensation methods were utilized to eliminate the disadvantage of charge imbalance between Al3+ and Mn2+. The results show that the luminescence intensity of Mn2+ was maximally enhanced by the introduction of Si4+ ions, which was 2.36 times that of the sample without charge compensator. Moreover, as the temperature reached at 150 °C, thermal stability of the samples contained charge compensator Li+ and Si4+ were improved to 93% and 90% of that the room temperature, respectively, while the original sample was 85%. These luminescence properties were enhanced due to the introduction of charge compensators which reduce defects caused by charge imbalance. In addition, the specific mechanisms were discussed in detail. In general, the charge compensation could be used as an effective strategy to strengthen thermal stability and luminescence performances of phosphors. [ABSTRACT FROM AUTHOR]

Abstract Upconversion (UC) optical thermometers using the fluorescence intensity ratio (FIR) technique arising from the thermally coupled energy levels (TCLs) are still suffering from low sensitivity owing to the restriction of small energy gap. In the present study, a strategy to strive for superior temperature sensitivity and signal discriminability is employed with the help of non-thermally coupled energy levels (NTCLs). A novel tri-doped Ba 3 Y 4 O 9 : Ho3+/Tm3+/Yb3+ phosphor with rhombohedral symmetry was successfully prepared via a solid-state reaction method, and the temperature sensing performance was evaluated by analyzing temperature-dependent upconversion emission spectra. The emission intensities of both Ho3+ and Tm3+ activators can be almost completely restored to their original values when the temperature of the sample is cooled to room temperature. The temperature-dependent FIR between NTCLs can be fitted well by a derived three-term equation with the correlation coefficient above 99.6%, and the FIR of NTCLs exhibits high temperature sensitivity over a wide temperature range owing to the different temperature responses of the NTCLs. The maximum absolute sensitivity S A and relative sensitivity S R values reaches as high as 0.0552 K−1 and 1.49% K−1, respectively, which are much higher than those of the previously reported bulk UC optical temperature sensing materials. Moreover, the emission bands of NTCLs are well separated, which endows the material a good signal discriminability for temperature detection. Excellent temperature sensing performance is also demonstrated in Er3+/Tm3+/Yb3+ tri-doped Ba 3 Y 4 O 9 , evidencing the validity of this strategy. These results indicate that the present UC materials can be potential candidates for optical temperature sensors, and the present strategy will provide a thought for developing other innovative UC temperature sensing materials. [ABSTRACT FROM AUTHOR]

The investigation on single phase multi-color phosphors is highly meaningful for near-ultraviolet chip based white light emitting diodes. In this work, a series of Eu 2+ and Tb 3+ singly doped and Eu 2+ /Tb 3+ codoped Sr 5 (PO 4 ) 3 Cl phosphors were synthesized via a high-temperature solid state reaction method. The luminescence spectra and decay curves of Eu 2+ and Tb 3+ singly doped samples were discussed, the optimal doping concentrations were determined. Thanks to the spectra overlap between Eu 2+ and Tb 3+ , nonradiative energy transfer from Eu 2+ to Tb 3+ was investigated. It is found electric dipole-dipole interaction played the main role for the energy transfer in codoped samples, the highest energy transfer efficiency was calculated to be 60.98%. Tunable emissions are observed for codoped samples by adjusting doping concentration. The thermal quenching properties were discussed and the activation energy (ΔE) was estimated in the present work. [ABSTRACT FROM AUTHOR]

Near-infrared phosphor-converted light emitting diodes (NIR pc-LEDs) is developing rapidly in plant cultivation because of its low cost, compact size and high efficiency. The NIR light of 700 ∼ 760 nm is known to be beneficial for seed germination and growth. Therefore, the exploration of NIR phosphors with specific wavelength and high efficiency is essential for the development of high-performance plant cultivation pc-LEDs. In this study, a highly efficient and thermal stable Cr3+ doped Lu 2 CaAl 4 SiO 12 (LCAS) phosphor with broadband NIR emission covering phytochrome P fr absorption range was successfully realized via Ca2+-Si4+ co-substitution of Lu3+-Al3+ pairs. The LCAS:0.07 Cr3+ exhibits a major emission peak of 740 nm with a FWHM of 160 nm and its internal/external quantum yield (IQY/EQY) is as high as 80%/30.5%. The integrated emission intensity of LCAS:0.07Cr3+ at 423 K lost only 33.8% of its initial intensity, indicating that it has a good thermal stability. When the LCAS:0.07Cr3+ was packaged into a pc-LED with a driving current of 320 mA, the device output power and photoelectric efficiency reached 90.6 mW and 8.6%, respectively, demonstrating that this phosphor has potential application in plant cultivation lighting. • A NIR phosphor LCAS: Cr3+ was successfully prepared. • The emission spectrum of LCAS: Cr3+ fits well with the absorption band of P fr. • The NIR phosphor exhibits relatively high IQE/EQE. [ABSTRACT FROM AUTHOR]

• A brand-new blue-emitting phosphor NaSrScSi 2 O 7 :Eu2+ was prepared. • NaSrScSi 2 O 7 :0.03Eu2+phosphor possesses a high absorption efficiency of 84.35%. • The blue phosphor allows the WLED-2 spectrum to cover more short-wavelength region. A high absorption efficiency blue-emitting phosphor NaSrScSi 2 O 7 :Eu2+ for near-UV-pumped white light-emitting diodes [Display omitted] The Eu2+ ion is extensively used as an activator due to its wide excitation band and high efficiency emission spectrum. However, most Eu2+-activated blue-emitting phosphors have low absorption efficiency in the near-ultraviolet (n-UV) region or lack the short-wavelength blue light emission (<450 nm), resulting in UV light leakage or poor color rendering. Herein, we have successfully prepared a brand-new blue phosphor NaSrScSi 2 O 7 : Eu2+ by solid-state reaction method. The Rietveld refinement of the powder diffraction data, luminescent properties, decay lifetime, quantum efficiencyand thermal quenching have been investigated in detail. Under 345 nm excitation, the NaSrScSi 2 O 7 : 0.03Eu2+phosphor manifests an asymmetric emission spectrum centered at 427 nm, and notably, shows a high absorption efficiency of 84.35%. Finally, we encapsulated two white light-emitting diodes (WLEDs) devices using as-prepared blue-emitting phosphor and three commercial phosphors. At 80 mA drive current, both packaged devices demonstrate warm white light. Meanwhile, the WLED-2 with NaSrScSi 2 O 7 : 0.03Eu2+ blue-emitting phosphor has a lower correlated color temperature of 3726 K, its spectrum complements more short-wavelength spectrum, and the special color rendering index R 6 and R 7 increased from 95.2, 94.5 to 98.3, 96.5, respectively, compared with WLED-1 without present phosphor. These results demonstrate that NaSrScSi 2 O 7 : Eu2+ blue-emitting phosphor is a prospective novel luminescent material for WLEDs. [ABSTRACT FROM AUTHOR]

• A cyan emission was achieved via the replacement of Si-N with Al-O in Ba 3 Si 6 O 12 N 2 :0.05Eu2+. • The emission peak could be shifted from 512 nm to 495 nm. • The emission intensity of the optimal cyan phosphor is 36% higher than Ba 3 Si 6 O 12 N 2 :0.05Eu2+. • The CCT of wLED decreases from 4407 K to 4038 K and the Ra increase from 85.8 to 90.8. Developing cyan phosphors excited by near ultraviolet (n-UV) or blue LED chips is extremely significant for making up for the cyan cavity of the existing white light emitting diodes (wLEDs). In this research, a cyan emission was successfully achieved via the replacement of Si-N with Al-O in Ba 2.85 Si 6 O 12 N 2 :0.15Eu2+ green phosphor. The emission peak could be shifted from 512 nm to 495 nm. The mechanism of spectral blue shift can be interpreted by the decrease of the crystal field splitting strength, which is induced by the square of the bond length and the decrease of centroid shift of 5d level, which is induced by the spectroscopic polarizability and 6th power of the bond length. The optimal cyan Ba 2.85 Si 5.65 Al 0.35 O 12.35 N 1.65 :0.15Eu2+ phosphor possess a broad excitation and emission band at the same time, whose emission intensity is 36% higher than that of Ba 2.85 Si 6 O 12 N 2 :0.15Eu2+. The CCT of the wLED with Ba 2.85 Si 5.65 Al 0.35 O 12.35 N 1.65 :0.15Eu2+ phosphor realizes from 4407 K to 4038 K and the Ra values achieve from 85.8 to 90.8. The results indicate that Ba 2.85 Si 6- y Al y O 12+ y N 2- y :0.15Eu2+ phosphor can serve as a cyan component for application in full-spectrum warm white lighting. [ABSTRACT FROM AUTHOR]

• A novel CsMoO 2 F 3 :Mn4+ oxyfluoride phosphor with high color purity was synthesized. • The CsMoO 2 F 3 :Mn4+ phosphor exhibits a remarkable negative thermal quenching. • The CsMoO 2 F 3 :Mn4+ phosphor demonstrates admirable color stability. Red-emitting phosphors composed of Mn4+-activated fluorides have attracted considerable interest for their applications in warm white light-emitting diodes (WLEDs). However, in addition to moisture instability, the unsatisfactory thermal stability of these phosphors limits their industrial applications. In this study, a novel red phosphor of CsMoO 2 F 3 :Mn4+ was synthesized via simple coprecipitation. This red phosphor exhibits an orthorhombic structure with a bandgap of ~3.43 eV. The Mn4+ ions occupy Mo6+ sites at the centers of [MoO 2 F 4 ]2− octahedrons. This phosphor shows narrow emission around ~633 nm excited by 450 nm blue-chip with high color purity of 99.58%. Satisfactorily, this phosphor exhibits excellent thermal stability and a strong negative-thermal-quenching. The total PL intensity of CsMoO 2 F 3 :3.88%Mn4+ phosphor at 275 K strengthens to ~540% relative to that at 25 K, and its relative emission intensity preserves about 129.3% when the temperature rises from room temperature to 423 K (150 ℃). It also shows admirable color stability with a slight chromaticity shift (ΔE) of only ~ 33.9 × 10 - 3 in the temperature region from 298 to 473 K. Furthermore, a warm WLED was fabricated by the mixture of red-emitting CsMoO 2 F 3 :3.88%Mn4+ and the yellow-emitting YAG:Ce3+ phosphors with a blue-emitting InGaN LED chip. The device exhibits low correlated color temperature (3983 K) and high color-rendering index (Ra = 81.3). With the increasing drive current from 20 mA to 120 mA, the chromaticity coordinate variation (CCV) is only (−0.0163, 0.0202). All these results indicate that the CsMoO 2 F 3 :Mn4+ phosphor holds tremendous potential for practical applications in high-power lighting and display with high-performance WLEDs. [ABSTRACT FROM AUTHOR]