A new CaF₂-YAG:Ce composite phosphor ceramic for high-power and high-color-rendering WLEDs

Thermally robust and optically transparent phosphor ceramics are now attracting great attention as promising luminescent materials for high-power white light-emitting diodes (WLEDs). Here, we report a new CaF₂-YAG:Ce phosphor ceramic in which the yellow-emitting YAG:Ce particles are embedded in a non-luminescent CaF₂ ceramic matrix. The composite phosphor ceramic was fabricated at a very low sintering temperature of 700 °C by using a simple hot-pressing method. No detectable interfacial reaction occurs between the YAG:Ce particle and the CaF₂ matrix. Owing to the excellent optical properties and high thermal conductivity of CaF₂, the prepared CaF₂-YAG:Ce phosphor ceramic shows a high quantum efficiency (IQE = 83.2%), and a low thermal quenching (only 9% loss in luminescence at 150 °C). WLEDs, fabricated by combining the CaF₂-YAG:Ce phosphor ceramic with a 460 nm blue chip of 2 W, exhibited bright white light with a luminous flux of 359.7 lm, a color temperature of 4021-7941 K and a color rendering index of 70.1-82.7. The composite phosphor ceramic showed a better performance than the traditional single-phase YAG:Ce ceramic, enabling it to be used in high-power WLEDs.