Thermoluminescence studies on γ-irradiated CaF2:Dy:Pb:Na single crystals

Thermoluminescence (TL) glow, thermoluminescence emission (TLE) and thermal decay (TD) of optical absorption (OA) bands were studied on γ-irradiated CaF2:Dy (0.010at.%):Pb (0.188at.%):Na (0.026at.%) single crystals (hereafter called crystal-I). The TL glow exhibited four glow peaks in the temperature region 300–600 K. The TL response with dose was studied up to ∼7.5 kGy. The total glow showed linear, supra linear and exponential growth with dose. The TLE showed bands characteristic of Dy3+ ions (around 1.65, 1.87, 2.18 and 2.63 eV) and sodium associated (SA) colour centres (CCs) such as MNa (around 1.67 eV) and XNa (a new SA CC, with an emission band around 2.63 eV). The OA bands of MNa CC around 3.23 and 2.07 eV were found to decrease with temperature almost in accordance with the TL glow. The R+A centre absorption around 2.48 eV was found to grow with temperature initially and then decayed. The formation/growth of the CCs R+A and XNa might be from the conversion of the irradiation produced CC MNa. An attempt was made to explain the TL mechanism in the present system.