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It has been one of the hot issues to prepare the red‐emitting Mn4+‐doped fluoride phosphors with highly efficient and waterproofness for warm white‐light‐emitting diodes (WLEDs) by the green and environmentally friendly method. Herein, we design a novel green molten salt route to synthesize K2SiF6:Mn4+ red powder using molten NH4HF2 salt instead of HF liquor as the reaction medium. The results show that KMnO4 and MnF2 could produce Mn4+ in NH4HF2 molten salt through a reduction reaction, and the resulting Mn4+‐doped K2SiF6 exhibited a bright red emission peaked at 632 nm under blue light excitation. The luminescence intensity of the as‐obtained product after immersing into water for 24 hours maintain nearly 100% of that before soaking and emission peak shape remains unchanged. The thermal stability of the sample was evaluated by temperature‐dependent luminescence spectral intensity during heating and cooling. Furthermore, a warm white‐light‐emitting diodes (WLEDs) with an excellent color rendering index (Ra = 87.1), lower correlated color temperature (CCT = 3536K), and high luminous efficacy (116.99 lm·W−1) was fabricated based on blue chip and K2SiF6:Mn4+ and commercial yellow phosphor (Y3Al5O12:Ce3+). [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 novel SrLu2O4: x Ho3+, y Yb3+ phosphors ( x=0.005-0.05, y=0.1-0.6) were synthesized by a simple solid-state reaction method. The phase purity, morphology, and upconversion luminescence were measured by X-ray diffraction ( XRD), scanning electron microscopy ( SEM), and photoluminescence ( PL) spectroscopy. The doping concentrations and sintering temperature were optimized to be x=0.01, y=0.5 and T=1400°C to obtain the strongest emission intensity. Under 980 nm laser diode excitation, the SrLu2O4:Ho3+, Yb3+ phosphors exhibit intense green upconversion ( UC) emission band centered at 541 nm (5F4,5S2→5I8) and weak red emission peaked at 673 nm (5F5→5I8). Under different pump-power excitation, the UC luminescence can be finely tuned from yellow-green to green light region to some extent. Based on energy level diagram, the energy-transfer mechanisms are investigated in detail according to the analysis of pump-power dependence and luminescence decay curves. The energy-transfer mechanisms for green and red UC emissions can be determined to be two-photon absorption processes. Compared with commercial NaYF4:Er3+, Yb3+ and common Y2O3:Ho3+, Yb3+ phosphors, the SrLu1.49Ho0.01Yb0.5O4 sample shows good color monochromaticity and relatively high UC luminescence intensity. The results imply that SrLu2O4:Ho3+, Yb3+ can be a good candidate for green UC material in display fields. [ABSTRACT FROM AUTHOR]