Defect states in Lu₃Ga_xAl_{5- x}O₁₂ crystals and powders

We study defect states in undoped and Eu³⁺-doped Lu ₃Ga_xAl_5-xO₁₂ (x = 0-5) garnet crystals by wavelength resolved thermally stimulated luminescence above room temperature. Eu³⁺ ions act not only as recombination centres but also as high temperature traps, as testified by the presence of a TSL peak at 450 °C correlated with Eu³⁺-doping. With increasing gallium content all glow peaks are shifted to lower temperatures. This trend is confirmed also for powder samples prepared by sol-gel technique. The observed low temperature shift of the glow peaks can be considered as a consequence of the band gap reduction following the increase of Ga³⁺ concentration. The comparison with the glow curve of a Ce³⁺-doped crystal is also shown.