Investigation of defect centres responsible for TL/OSL in MgAl2O4:Tb3+

Magnesium aluminate doped with Tb3+ (MgAl2O4:Tb3+) was prepared by combustion synthesis. Three thermoluminsence (TL) peaks at 120, 220 and 340 °C were observed. PL and TL emission spectrum shows that Tb3+ acts as the luminescent centre. Optically stimulated luminescence (OSL) was observed when stimulated by 470 nm blue light. Electron spin resonance (ESR) studies were carried out to identify the defect centres responsible for the TL and OSL processes in MgAl2O4:Tb3+. Two defect centres were identified in irradiated MgAl2O4:Tb3+ phosphor by ESR measurements which was carried out at room temperature and these were assigned to V and F+ centres. V centre (hole centre) is correlated to 120 and 220 °C TL peaks and F+ centre (electron centre), which acts as a recombination centre is correlated to 120, 220 and 340 °C.