Effect of Li+ co-doping on the luminescence and defects creation processes in Gd3(Ga,Al)5O12:Ce scintillation crystals.

Photo- and thermally stimulated luminescence characteristics, as well as photostimulated defects creation processes are investigated in the 85–510 K temperature range for the Li+ co-doped single crystal of Gd 3 (Ga,Al) 5 O 12 :Ce (GAGG:Ce). The results for GAGG:Ce,Li are compared with the corresponding characteristics of the GAGG:Ce and GAGG:Ce, Mg single crystals of similar host composition. The influence of Li+ and Mg2+ ions on the Ce3+ - related emission band position, temperature dependence of the photoluminescence intensity, efficiency of the Gd3+ → Ce3+ energy transfer, intensity and decay kinetics of the afterglow, and thermally stimulated luminescence characteristics is revealed. The presence of the Ce3+ → Ce4+ conversion in GAGG:Ce,Li is confirmed. The conclusion is made that, unlike GAGG:Ce,Mg, the compensation of the Li+ excess negative charge in GAGG:Ce,Li occurs due to both the Ce3+ → Ce4+ conversion and the effective formation of intrinsic crystal lattice defects. The origin of these defects as well as the origin of the electron and hole trapping centers in the GAGG:Ce,Li crystal are discussed. The defects responsible for the low-temperature TSL glow curve peak can appear in the GAGG:Ce,Li crystal for the Li+ - induced excess volume and excess negative charge compensation. Besides, the Li+ ions can stimulate the formation in the crystal of hole centers which are most probably of the O− - type centers [35]. The O− - Li+ centers will be most probably responsible for the high-temperature peaks, like the O− - Mg2+ centers. Moreover, the lack of positive charge in lattice can stimulate creation of single O− centers with low thermal stability. • Photo- and thermally stimulated luminescence of Gd3(Ga,Al)5O12:Ce single crystals co-doped with Li+ is investigated. • Co-doping with Li + leads to both the Ce3+.→ Ce4+ conversion and the formation of intrinsic defects; • Origin of the Li + -induced crystal lattice defects is considered. • Influence of the Li + co-doping on scintillation characteristics of Gd3(Ga,Al)5O12:Ce is discussed. [ABSTRACT FROM AUTHOR]