Defect states and temperature stability of Eu2+ center in Eu-doped yttrium aluminum garnet

We study defect states in Eu-doped Y3Al5O12 powder by thermally stimulated luminescence (TSL) in the temperature range 77-500 K. We identify the main TSL peaks, analyze them by the initial rise technique and calculate the characteristic parameters of the corresponding traps. Tunneling of charge carriers between traps and recombination centers up to about 265 K is observed and discussed. Recent study established the presence of both Eu2+ and Eu3+ centers in the studied Y3Al5O12 powder. The TSL spectra show that Eu2+ and Eu3+ centers compete in the charge carrier capture. We show that previously observed Eu2+ luminescence quenching is due to both classical thermal quenching and thermal ionization of the Eu2+ excited state. We model the temperature dependence of the delayed recombination intensity.