YAGG:Ce Phosphor-in-YAG Ceramic: An Efficient Green Color Converter Suitable for High-Power Blue Laser Lighting

Thermally robust phosphor ceramics are an ideal color converter for high-power laser lighting applications. However, high-quality white light is difficult to achieve due to the absence of green and red emission materials. AnY3Al5–xGaxO12:Ce3+ (YAGG:Ce3+) ceramic can emit green light, while the strong oxidizing atmosphere is needed to suppress the Ga evaporation during the high-temperature fabrication process, which can seriously decrease the luminescence efficiency. To enable the green-emitting YAGG:Ce3+ material for laser lighting application, we report a composite phosphor ceramic for which the first achieved fine-grained YAGG:Ce3+ phosphor powders were dispersed into a YAG ceramic matrix (YAGG:Ce-YAG). The transmittance of the YAGG:Ce-YAG ceramic can reach 62% at a range of 500–800 nm owing to the similar refractive index and structure of two phases. The resulting phosphor ceramic also exhibits a high external quantum efficiency (EQE = 68.3%) and excellent thermal stability (luminescence intensity: 90% retention at 200 °C) close to those of the original phosphor powders. Furthermore, due to the superior thermal conductivity of the YAGG:Ce-YAG phosphor ceramic (9.4 Wm–1 K–1 at room temperature), a high luminous emittance of 700 lm/mm2 can be achieved under an excitation of 8.2 W/mm2 blue laser light. The achieved YAGG:Ce-YAG phosphor ceramic shows a promising application as the green color converter for high-power laser lighting.