The effects of Mg2+/Si4+ co-substitution for Al3+ on sintering and photoluminescence of (Gd,Lu)3Al5O12:Ce garnet ceramics

A series of phase-pure [(Gd 0.6 Lu 0.4 ) 0.99 Ce 0.01 ] 3 [Al 1- z (Mg/Si) z ] 5 O 12 ( z = 0-0.10) garnet phosphor powders were prepared via gel-combustion, which were then sintered into ceramics (up to 1550 °C) under atmospheric pressure. Dilatometry revealed that equimole of Mg 2+ /Si 4+ substitution for Al 3+ accelerates densification and lowers the activation energy for grain boundary diffusion in the intermediate stage of sintering (∼1150–1370 °C), which was assayed to be ∼353 kJ/mol for z = 0 and ∼289 kJ/mol for z = 0.10. The acceleration effects of Mg 2+ /Si 4+ on sintering and grain growth were further demonstrated by the results of ramp and holding sintering. Firing at 1550 °C for 4 h also produced ∼99 % dense ceramics for the Mg 2+ /Si 4+ codoped garnet powders. Through considering crystal splitting of the Ce 3+ 5d energy level, photon-phonon coupling, and crystal structure/microstructure, the influences of Mg 2+ /Si 4+ content and material form on Ce 3+ luminescence, including intensity, external/internal quantum efficiencies, emission wavelength, CIE color coordinates and decay time, were clarified in detail.