Spectrally Tunable Dual‐Phosphor Ceramics for Laser Lighting

Abstract Luminescent composite ceramics with two or more distinct phosphors are required to finely control the optical properties of laser‐driven solid‐state lighting, but they are hardly densified due to their different sintering temperature and chemical reactions between them. Then, highly dense and efficient dual‐phosphor ceramics consisting of orange‐emitting Ca‐α‐SiAlON:Eu and yellow‐emitting YAG:Ce phosphors is successfully prepared by spark plasma sintering. Fine Ca‐α‐SiAlON:Eu powders and Al 2 O 3 ‐coated YAG:Ce (YAG:Ce@Al 2 O 3 ) powders are used as raw materials, which enable to obtain dense Al 2 O 3 ‐Ca‐α‐SiAlON:Eu (Ceramic‐Ca) and Al 2 O 3 ‐Ca‐α‐SiAlON:Eu‐YAG:Ce@Al 2 O 3 (Ceramic‐Ca+Y@Al 2 O 3 ) ceramics at 1480 °C. The chemical reaction between Ca‐α‐SiAlON:Eu and YAG:Ce can be hindered by using the Al 2 O 3 surface coating, and the photoluminescence properties of both phosphors are thus remainedduring high‐temperature sintering. The Ceramic‐Ca+Y@Al 2 O 3 show tunable spectra with emission maximum ranging from 541 to 601 nm, an external quantum efficiency of ≈42%, thermal conductivity of >17.6 W m −1 K, maximal luminance saturation of 18.8 W mm −2 , excellent thermal and color stabilities. It demonstrates that the dual‐phosphor ceramics containing equivalent Ca‐α‐SiAlON:Eu and YAG:Ce allow to create super‐brightness laser lighting with an output luminous flux density of 782.5 lm mm −2 and a color temperature of 2278 K. This work paves an avenue to fabricate multi‐phosphor composite ceramics for color‐temperature‐tunable laser‐driven white light.