CaAlSiN3:Eu2+ translucent ceramic: a promising robust and efficient red color converter for solid state laser displays and lighting

Abstract

As an excellent red phosphor, CaAlSiN₃:Eu²⁺ plays a major role in high color rendition or wide color gamut white light-emitting diodes, but it can hardly be used in high-power laser displays and lighting due to the intrinsic low thermal performance of the phosphor/silicone resin mixture. To apply CaAlSiN₃:Eu²⁺ in laser lighting devices, a bulk ceramic form is thus required to survive thermal attack and high flux density irradiation. However, it remains an unsolved great challenge to fabricate fully densified CaAlSiN₃:Eu²⁺ ceramics. Here, for the first time, translucent CaAlSiN₃:Eu²⁺ ceramics with an interesting composite microstructure, where red-emitting phosphor particles with a core–shell structure are uniformly embedded in a non-luminescent α-Sialon matrix, are successfully synthesized using Si₃N₄ and SiO₂ as sintering additives. The luminescence ceramic is superior to the corresponding powder phosphor in terms of its enhanced thermal stability (15% increase) and thermal conductivity (4 W m⁻¹ K⁻¹). It has a high external quantum efficiency of 60% (87% that of the powder) upon 450 nm excitation, and a luminous efficacy of 10.6 lm W⁻¹ when irradiated under a blue laser flux density of 0.75 W mm⁻². The translucent CaAlSiN₃:Eu²⁺ ceramic is thus supposed to be a potential color converter used in emerging laser lighting and display technologies.