Photoluminescence optical and thermal quenching in heavily doped Gd3(Ga,Al)5O12:Ce, Mg single crystals: Dependence on the Ga3+, Ce3+, and Mg2+ concentration

Heavily doped single crystals of Gd 3 Ga x Al 5-x O 12 :Ce, Mg (x = 2.46–2.95) with different concentrations of Ce (0.016–0.188 at.%) and Mg (0–0.083 at.%) are investigated by the X-ray diffraction, photoluminescence , and thermoluminescence methods . Dependences of the luminescence characteristics, as well as crystal lattice parameters and distances between the Ce 3+ and Mg 2+ ions, on the Ga, Ce, and Mg concentration are studied. Mechanisms of the processes, resulting in the photoluminescence optical and thermal quenching and acceleration of decay kinetics, and the influence of the crystal composition on these processes are discussed. The role of close {Ce 3+ - Mg 2+ Ga } pairs in these processes is considered. At T > 400 K, the luminescence thermal quenching is caused by the crossover process, while in the 200–350 K temperature range, by the electron transfer from the 5d 1 excited state of Ce 3+ to nearby defect levels (electron traps) located between the 5d 1 level and the conduction band . The latter process results also in the appearance of thermally stimulated luminescence, and its efficiency depends on the Ga 3+ content and concentration of intrinsic defects. The optimum concentrations of Ga 3+ and Mg 2+ ions in the investigated crystals are determined. • XRD, PL, and TSL of heavily doped Gd 3 Ga x Al 5-x O 12 :Ce, Mg crystals are studied. • Mechanisms of optical and thermal quenching of Ce 3+ luminescence are discussed. • Role of Mg 2+ in decay kinetics acceleration and light yield reduction is clarified. • At RT, these processes are mainly influenced by Ga 3+ content and intrinsic defects. • Optimum concentrations of Mg 2+ (0.035 at.%) and Ga 3+ (x = 2.65) are determined.