Thermoluminescence and persistent luminescence of Tb3+ activated CaYAl3O7

Persistent emission (more than 1.5 h) was observed in Tb3+-doped CaYAl3O7 (CYAM) samples after X-ray or UVC excitation. Thermoluminescent (TL) emission spectra showed that Tb3+ emission is responsible for the TL emission signal, indicating a mechanism with a single recombination and luminescence centre. The shape of TL peaks showed overlap of peaks, and thus more than one trapping centre, and this result was confirmed through T-m x T-STOP analysis. TL measurements as function of doses revealed that the TL peak positions do not change with increasing doses of UVC irradiation, which means that all TL peaks can be well described by first-order kinetics. The initial rise method was used to determine the activation energies, whereas E (eV) x T-stop plot showed a distribution of activation energy ranging from 1.1 to 1.3 eV. These depth traps were assigned to intrinsic defects in the host. Possible mechanisms were discussed considering the 4f ground state of Tb3+ and oxygen vacancies as recombination and trapping centres, respectively.