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 [(Gd0.6Lu0.4)0.99Ce0.01]3[Al1-z(Mg/Si)z]5O12 (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 Mg2+/Si4+ substitution for Al3+ 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 Mg2+/Si4+ 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 Mg2+/Si4+ codoped garnet powders. Through considering crystal splitting of the Ce3+ 5d energy level, photon-phonon coupling, and crystal structure/microstructure, the influences of Mg2+/Si4+ content and material form on Ce3+ luminescence, including intensity, external/internal quantum efficiencies, emission wavelength, CIE color coordinates and decay time, were clarified in detail.