Non-spherical pore scattering-enhanced YAG:Ce3+, Cr3+ ceramics: efficient light converters for high-brightness laser illumination

Abstract

The purpose of this investigation is to address the issues of insufficient thermal stability and spectral narrowing of conventional phosphor materials in high-power laser illumination. A new type of YAG:Ce³⁺, Cr³⁺ porous phosphor ceramic was developed in this paper through the design of tunable pore structure. The porous ceramics with controllable porosity (5–20 vol%) were successfully fabricated by using spherical micron-sized polymethyl methacrylate (PMMA) as the pore-forming agent and combining it with a vacuum sintering process. The porous structure effectively suppresses total reflection, thereby enhancing light extraction in specific directions. The experimental findings demonstrate that the 5–10% porosity design can substantially enhance the light extraction efficiency. In the context of blue laser excitation below 450 nm, the luminous flux of the 5% porosity ceramics was determined to be 1178 lm, while the luminescence efficiency remained consistent at 80 lm W⁻¹ under high-power excitation of 15 W. This corresponds to a 23% improvement in luminescence efficiency compared with that of dense YAG:Ce³⁺, Cr³⁺ ceramics (65 lm W⁻¹). Concurrently, it suppresses the total reflection loss through the refractive index gradient, which shifts the CIE coordinates to the orange-red direction (Δx = +0.03, Δy = −0.04). The resultant colour rendering index (CRI) is a maximum of 70. This study proposes an innovative phosphor ceramic design solution for high-brightness laser lighting, demonstrating both efficient light conversion and thermal management capabilities.