Spectral, energy resolution properties and green-yellow LEDs applications of transparent Ce3+:Lu3Al5O12 ceramics

Transparent Ce3+:Lu3Al5O12 ceramics were successfully fabricated by combining tape-casting method and direct-forming method with solid-state sintering. The in-line optical transmittance and absorption spectra of as-sintered and air-annealed Ce:LuAG ceramics were comparely studied. XPS spectra indicated Ce3+ and Ce4+ ions co-existed in the prepared ceramics. Energy levels splitting of Ce3+ in LuAG hosts were investigated based on broad-band emission from 500 nm to 700 nm resulting from the electron transitions from 5d1 excited levels (2D) to 4f ground state of Ce3+ (2F5/2, 2F7/2). The fluorescence lifetimes at 540 nm were 50-60 ns and energy resolution of 12% was achieved at 22Na (511 keV). When collaborated with InGaN-GaN LED chips, a maximum CRI of 55.8 with LE as high as 223.4 lm/W were demonstrated, indicating that Ce:LuAG ceramics had a promising potential for white light-emitting diodes.