High quantum efficiency Ce:(Lu,Y)3(Al,Sc)2Al3O12 transparent ceramics with excellent thermal stability for high-power white LEDs/LDs

Abstract

Transparent ceramics (TCs) with high quantum efficiency and excellent thermal stability are essential for the applications in high-power remote excitation white light-emitting diode or laser diode (LED/LD) lighting devices as color convertors. In this study, based on the “local complexity of Ce³⁺ ion coordination environment effect” and “effective ionic radius match effect”, an effective regulation of the phase composition and spectral properties was realized in LuAG TCs by incorporating Y³⁺ and Sc³⁺ ions. A series of Ce:(Lu,Y)₃(Al,Sc)₂Al₃O₁₂ (Ce:LuYSAG) TCs were fabricated with a high internal quantum efficiency (IQE) of 86.7%. The prepared TCs exhibited a distinct red-shift (520 → 541 nm) and a 10.2% increase of full width at half maximum (FWHM) in the emission spectra. Surprisingly, 89.9% of the room temperature emission intensity of the TC was retained at 200 °C. By combining the Ce:LuYSAG TCs with a 460 nm blue chip or a 455 nm laser source, white LED/LD devices in a remote excitation mode were constructed. A tunable hue from cyan-green to pale-green was obtained with increasing Y³⁺ concentration of TCs. The surface temperature of TCs varied from 112.6 °C to 62 °C under 1.0 W LD irradiation. Upon increasing the power of the blue laser from 1.0 W to 3.5 W, the luminous flux (LF) of the TC with 30 at% Sc³⁺ and 50 at% Y³⁺ ions substitution tremendously increased from 250.9 lm to 877.4 lm, and the optimized luminous efficiency of radiation (LER) was as high as 251 lm W⁻¹. Therefore, this work opens up new opportunities for the development of TCs with excellent luminescence performance through manipulation of their local coordination structure for high-power white LEDs/LDs.