Low temperature recombination luminescence of Mg3Y2Ge3O12:Tb³⁺

A study was conducted to examine the recombination processes in persistent phosphor Mg₃Y₂Ge₃O₁₂:Tb³⁺ garnet at low temperatures. Photoluminescence (PL), recombination luminescence (RL), electron paramagnetic resonance (EPR), and EPR detected by PL or RL were measured. In samples with low Tb³⁺ concentration, a broad PL and RL band around 400–450 nm and characteristic Tb³⁺ lines were observed. However, in samples with high Tb³⁺ concentration, only Tb³⁺ lines were present. Both the broad-band and the line components exhibit long-lasting tunneling luminescence with hyperbolic decay. After 263 nm UV irradiation signals of intrinsic electron (F-type) and hole (V-type) trapping centres were observed in the EPR spectra. Such signals were also observed in RL-detected EPR spectra, indicating that the broad RL band at low Tb³⁺ concentrations originates from tunneling recombination between these intrinsic traps. At high Tb³⁺ concentrations, the RL-EPR spectrum was not observed, suggesting that intrinsic electron and Tb-related hole trapping centres probably participate in the tunneling recombination.