High homogeneity, thermal stability and external quantum efficiency of Ce:YAG single-crystal powder phosphors for white LEDs

抄録

The properties of Ce:Y₃Al₅O₁₂ single-crystal powder phosphors, obtained by powdering single-crystals, are investigated as a function of the average grain size. It is found that single-crystal powders maintain the outstanding properties of bulky crystals, namely a high internal quantum efficiency and thermal stability. Furthermore, single-crystal powders exhibit a very high homogeneity and reproducibility, which contrasts with the large variation of emission intensity in reference ceramic powders of highest quality. The effective absorption of single-crystal phosphors increases with the grain size and it is enhanced by a treatment with HF. An effective absorption comparable with the one of reference ceramic powder phosphor is obtained, even though the Ce concentration in single-crystal phosphor powders is about one order to magnitude lower.