Development of glass ceramic phosphors for white LEDs

Abstract

We have developed glass ceramic materials precipitated with Ce:YAG phosphor microcrystals for white LEDs. After preparing mother glasses with a composition of Y₂O₃-Al₂O₃-SiO₂ doped with Ce₂O₃ by conventional melting, materials containing 40% volume fraction of YAG as a single phase can be obtained by heat treatment above 1200°C. The materials are translucent and exhibit fluorescent characteristics equivalent to those of the powder Ce : YAG phosphor, absorbing 460nm blue light and exhibiting a broad photoluminescence band due to the Ce³⁺: 5d→4f transition. Since 60% of the material is composed of silicate matrices, the glass ceramics show excellent durability against heat and humidity and thus are expected to be used as a phosphor plate in high-power white LEDs for the general illumination in the near future.