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Abstract: We study lutetium hafnate, Lu4Hf3O12, prepared by acetate and citrate combustion in the form of nanometric powders. Optical properties including X-ray excited luminescence, steady-state and time resolved photoluminescence as well as thermally stimulated luminescence are investigated for undoped as well as Eu3+ and Tb3+ doped samples. We identify recombination centers in the host matrix and we tentatively associate the principal emission with a radiative transition of the F+ center. We also demonstrate that athermal tunneling of charge carriers between traps and recombination centers is the predominant mechanism of delayed radiative recombination following irradiation by ionizing radiation. [Copyright &y& Elsevier]

Abstract: We study defect states in undoped and Eu3+-doped Lu3Ga x Al5− x O12 (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. [ABSTRACT FROM AUTHOR]