Highly thermal conductive red-emitting AlN-CaAlSiN3:Eu2+ composite phosphor ceramics for high-power laser-driven lighting

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Thermally robust red-emitting phosphor ceramics are urgently required for laser lighting and displays with high luminance and better color saturation. The most promising CaAlSiN3:Eu ceramics have a low thermal conductivity of 4.2 W m−1 K−1 and a small luminance saturation of 0.5 W, making it hard to be used under high power laser irradiation. In this work, we incorporated AlN into the CaAlSiN3:Eu ceramic to produce red-emitting AlN-CaAlSiN3:Eu composite phosphor ceramics by spark plasma sintering. The fully densified phosphor ceramics have the highest thermal conductivity reported so far (53.5 W m−1 K−1), which is about 13 times higher than the reported one. The luminance saturation of the composite ceramics occurs at a high threshold of 4.2 W under blue laser excitation, enabling them to be used for high power laser lighting. This work provides an idea of tackling the microstructure of nitride phosphor ceramics and of preparing thermally robust red-emitting color converters.