Biphasic (Lu,Gd)3Al5O12-based transparent nanoceramic color converters for high-power white LED/LD lighting

Abstract

Ce doped Lu3Al5O12 (Ce:LuAG) transparent ceramics are considered as promising color converters for solid-state lighting because of their excellent luminous efficiency, high thermal quenching temperature, and good thermal stability. However, Ce:LuAG ceramics mainly emit green light. The shortage of red light as well as the expensive price of Lu compounds are hindering their application for white lighting. In this work, transparent (Lu,Gd)3Al5O12–Al2O3 (LuGAG–Al2O3) nanoceramics with different replacing contents of Gd3+ (10%–50%) were successfully elaborated via a glass-crystallization method. The obtained ceramics with full nanoscale grains are composed of the main LuGAG crystalline phase and secondary Al2O3 phase, exhibiting eminent transparency of 81.0%@780 nm. After doping by Ce3+, the Ce:LuGAG–Al2O3 nanoceramics show a significant red shift (510 nm→550 nm) and make up for the deficiency of red light component in the emission spectrum. The Ce:LuAG–Al2O3 nanoceramics with 20% Gd3+ show high internal quantum efficiency (81.5% in internal quantum efficiency (IQE), 96.7% of Ce:LuAG–Al2O3 nanoceramics) and good thermal stability (only 9% loss in IQE at 150 ℃). When combined with blue LED chips (10 W), 0.3%Ce:LuGAG–Al2O3 nanoceramics with 20% Gd3+ successfully realize the high-quality warm white LED lighting with a color coordinate of (0.3566, 0.435), a color temperature of 4347 K, CRI of 67.7, and a luminous efficiency of 175.8 lm·W−1. When the transparent 0.3%Ce:LuGAG–Al2O3 nanoceramics are excited by blue laser (5 W·mm−2), the emission peak position redshifts from 517 to 570 nm, the emitted light exhibits a continuous change from green light to yellow light, and then to orange-yellow light, and the maximum luminous efficiency is up to 234.49 lm·W−1 (20% Gd3+). Taking into account the high quantum efficiency, good thermal stability, and excellent and adjustable luminous properties, the transparent Ce:LuGAG–Al2O3 nanoceramics with different Gd3+ substitution contents in this paper are believed to be promising candidates for high-power white LED/LD lighting.

Keywords

• glass crystallization
• (lu,gd)3al5o12 (lugag)–al2o3 nanoceramics
• high-power wleds/lds
• white lighting