Enhanced efficiency and thermal performance of multistage gradient doping Ce:YAG transparent ceramics for laser lighting

The key to realizing the applications of ceramic based laser lighting devices depends on the heat management capability of color converters. In order to sufficiently absorb the blue light and smoothen the temperature gradient of luminescent ceramics, multistage gradient doping Ce3+:Y3Al5O12 (Ce:YAG) transparent ceramics (TCs) with five different concentrations were designed, including 0.01 at.%, 0.05 at.%, 0.1 at.%, 0.2 at.% and 0.4 at.% Ce. The composite green bodies were prepared by aqueous tape casting and multistage gradient doping Ce:YAG TCs, with concentrations from low to high, were fabricated by vacuum sintering. The in-line transmission values at 800 nm of composite structure Ce:YAG TCs could reach 80.3%. Under 21.13 W/mm2 blue laser excitation, the gradient doping Ce:YAG TC (1.32 mm) realized a high luminous efficacy of 280.3 lm/W, which was 15.8% higher than that of 0.15 at.% Ce:YAG TC (240.27 lm/W). Finally, during lighting process, the input-output temperature differences (Tin-Tout) between excitation surface and light-exit surface of 0.15 at.% Ce:YAG TC was 5 ℃, while that in gradient doping TC reduced by 50% (2.5 ℃). The results indicate that the multistage gradient doping Ce:YAG TCs will be an interesting color converter for high-power and energy-saving laser-driven lighting.