Thermally stimulated luminescence and electron paramagnetic resonance studies of doped K3Na(SO4)2

Rare earth and actinide doped alkali and alkaline earth sulphates, exhibit a variety of point defects stabilized due to the charge imbalance/self-irradiation and they play an important role in luminescence properties. In this paper, we report the point defects formed in the mixed sulphate K3Na(SO4)2 on doping with the radio-active rare earth element 147 Pm as studied by TSL and EPR techniques. EPR studies on self and gamma irradiated samples showed the signal due to the radical pair, SO4−–SO3− in addition to the signals from SO4−, SO3− and O2− ions. However EPR spectra of electron beam irradiated (undoped) K3Na(SO4)2 samples did not show the presence of the radical pair SO4−–SO3−, indicating the importance of dopant per se, in stabilizing the radical pair. EPR studies of 147 Pm doped samples annealed at different temperatures after gamma irradiation showed that SO4−–SO3− radical pair gets destroyed around 550 K , whereas SO4− ion gets annealed in the temperature range 375– 450 K . SO3− ion was found to be stable upto 600 K . From TSL–EPR correlation, it is inferred that the release of trapped hole at SO4− ion on heating leads to the formation of SO 4 2− ∗ and energy transfer to Pm3+ ion, results in the glow peak at 415 K .