Role of defect centres in thermoluminescence mechanism of Tb³⁺doped MgAl₂O₄

Abstract

Magnesium aluminate (MgAl₂O₄) doped with terbium was prepared by combustion synthesis. Defect centres of MgAl₂O₄:Tbare studied by correlating various techniques such as Electron Spin Resonance (ESR), Thermoluminescence (TL) and Optically Stimulated Luminescence (OSL). TL studies on MgAl₂O₄:Tb³⁺ show two TL peaks at 120 and 340°C. MgAl₂O₄:Tb³⁺ exhibits OSL when stimulated with 470 nm blue light. ESR study shows two defect centres with <i>g</i> = 2.011 and <i>g</i> = 2.0052 which are assigned to V- centre and F⁺ centre, respectively. Step annealing ESR technique study suggests that V-centre is correlated to 120°CTL peak whereas F⁺ centre is correlated with both the 120 and 340°C TL peaks. A TL mechanism is proposed. ESR–OSL correlation studies are carried out. The results of ESR-OSL correlation study along with TL bleaching study support the proposed TL mechanism of 120°C TL peak.