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YAG:Ce/YAG:Cr/YAG:Pr composite phosphor ceramics with barcode structure were prepared by tape casting combined with the solid‐state reaction method. This structure provides a convenient and effective method for regulating the optical parameters such as luminous efficacy (LE), color rendering, and correlated color temperature (CCT) of white light‐emitting diodes/laser diodes (LEDs/LDs). For the sample with a thickness ratio of 6:6:6 for YAG:Ce, YAG:Cr, and YAG:Pr, the in‐line transmittance reaches 60% at 800 nm, and it shows a good optical performance with the LE of 106 lm/W, the color gamut (Rg) of 77, the color fidelity index (Rf) of 86, and the CCT of 7642 K. The electroluminescence spectra and color coordinates can be adjusted by changing the ratio of each component in the composite ceramic and the thickness of the ceramic because the tape casting method allows precise control of the thickness of each ceramic layer. The high tunability provides more freedom in the performance design of composite phosphor ceramics and makes them the most promising candidate for high brightness white LEDs/LDs. [ABSTRACT FROM AUTHOR]

In this work, a series of Al2O3–Ce:YAG phosphor powders were synthesized by regulating the excess Al3+ of (Y,Ce)3Al5O12 via coprecipitation method for the first time, where Al3+, Ce3+, and Y3+ elements were uniformly distributed. With the increase of Al3+ content, the morphology of the powders changed from wormlike shapes to flaky shapes, and Y3Al5O12 phases had a tendency to convert to YAlO3 phases. The x wt.% Al2O3–(Y0.999Ce0.001)3Al5O12 (x = 20, 30, 40, 50, 60, and 70) composite phosphor ceramics (CPCs) were obtained by vacuum sintering (1775°C × 10 h), where Al2O3 and Ce:YAG phases were also well‐distributed. When the Al2O3 content was 30–40 wt.%, the average grain size of Al2O3 was close to that of Ce:YAG. A solid‐state laser lighting device was constructed by a 450 nm laser source and CPCs in a reflection mode. By adjusting the laser power, the correlated color temperature (CCT) values of white laser diodes (LDs) were achieved close to the standard white light of 6500 K. Impressively, the white LDs equipped with the 40 wt.% Al2O3‐containing CPCs showed the optimum CCT of 6498 K (color coordinates: 0.31 and 0.38), as well as a high luminous flux of 1169 lm and efficiency of 166 lm/W at the LD power of 7.05 W. This work has provided a potential idea to optimize the composition uniformity of Al2O3–Ce:YAG CPCs as also to explore their excellent performance in the application of white laser lighting. [ABSTRACT FROM AUTHOR]

Based on the "effective ionic radius match effect" and the "charge balance substitution rule of ions", mixed Ba2+, Al3+, Lu3+, and Ce3+ ions can be effectively regulated to a BaAl 2 O 4 -LuAG:Ce biphasic structure. The contribution of BaAl 2 O 4 like as scattering centers can reduce overall reflection losses and enhance the light extraction efficiency of these composite phosphor ceramics (CPCs). In this work, a series of x wt.% BaAl 2 O 4 -LuAG:Ce (x = 0, 3, 5, 10, 15) CPCs were fabricated by vacuum sintering using co-precipitated composite powders. Homogenization at the atomic level of mixed Ba3+, Al3+, Lu3+, and Ce3+ ions in multiphase powders provides uniform distribution of BaAl 2 O 4 and LuAG:Ce constituent phases in composite ceramics. The introduction of BaAl 2 O 4 has an additive effect, which also consists in uniform aggregation of pores near their grains during sintering. It allows to adjust the size and amount of microstructural defects by varying the secondary phase content. Under the excitation of 10.8 W 450 nm LDs in a reflection mode, 3 wt% BaAl 2 O 4 -based CPCs show the optimum luminous flux of 2244 lm and a luminous efficiency of 208 lm·W−1. The obtained CPCs show a high application potential in solid-state laser lighting. • Mixed Ba2+, Al3+, Lu3+, and Ce3+ ions can be effectively regulated to a BaAl 2 O 4 -LuAG:Ce biphasic structure. • BaAl 2 O 4 acting as scattering centers can reduce overall reflection losses. • BaAl 2 O 4 has an additive effect to adjust the size and amount of microstructural defects. • BaAl 2 O 4 -based CPCs shows luminous flux of 2244 lm and a luminous efficiency of 208 lm·W−1. [ABSTRACT FROM AUTHOR]

Compared to phosphor and phosphor in glass, phosphor ceramics have higher thermal properties, and are less prone to thermal quenching. (Ce,Lu) 3 Al 5 O 12 (Ce:LuAG) has better thermal stability than most of the phosphors, such as (Ce,Y) 3 Al 5 O 12 (Ce:YAG). However, the high melting point of Lu 3 Al 5 O 12 (LuAG; up to 2010 °C) presents a great challenge in producing transparent ceramics (TCs), so a series of Ce:LuAG nanopowders with high sintering activity were prepared by the co-precipitation method and then used as initial materials to obtain x at.% Ce:LuAG (x = 0.05, 0.1, 0.2, 0.3, 0.35, 0.4, 0.5, 0.55, 0.6, 0.65, 0.7) TCs by vacuum sintering at 1775 °C for 10 h. Moreover, the luminous properties of typical Ce-doped LuAG phosphors were systematically investigated using excitation by light-emitting diodes or laser diodes (LEDs/LDs). The emission intensity of 0.4 at.% Ce doped sample is the highest among all TCs with Ce amount ranging from 0.05 to 0.7 at.% at room temperature. The photoluminescence intensity of 0.4 at.% Ce:LuAG only decreases by 12.5% from 25 to 225 °C. The 0.4 at.% Ce:LuAG based on 0.8 W LEDs and 1.1 W LDs has the optimum luminous flux of 71.5 and 113.7 lm and the luminous efficiency of 89.3 and 101.4 lm∙W−1, respectively. As Ce concentration increases, a decrease in the luminescence saturation threshold of TCs is observed with a blue laser power density of 2.5–36.9 W∙mm−2. A high-flux yellow-green light of 1166.9 lm is obtained from 0.1 at.% Ce:LuAG when excited with a high-power LD with an energy density of 36.9 W∙mm−2. This work explored the best Ce doping level in Ce:LuAG TCs, as well as the luminescence saturation threshold in remote laser lighting applications. • Ce:LuAG transparent ceramic phosphors were prepared by vacuum sintering from co-precipitated nanopowders. • The emission intensity of 0.4 at% Ce:LuAG ceramic phosphor is among the highest with Ce-doping from 0.05 to 0.7 at%. • The photoluminescence intensity of 0.4 at% Ce:LuAG ceramic phosphor only decreases by 12.5% from 25 to 225 °C. • A high-flux yellow-green light of 1166.9 lm was obtained from 0.1 at% Ce:LuAG when excited with a high-power LD. [ABSTRACT FROM AUTHOR]