Effect of deformation on the thermoluminescence of BaSO4:Tb phosphors

Thermoluminescence (TL) of BaSO4 phosphors has been studied. BaSO4:Tb phosphors having different concentration of Tb were prepared by solid state reaction method and their TL has been studied after gamma irradiation. Two distinct peaks are observed in the TL glow curve, one around 150 degrees C and another around 210 degrees C. It is also observed that TL peak at 150 degrees C increases with gamma dose given to the samples. However, TL peak around 210 degrees C saturates for gamma dose higher than 0.930 kGy. In order to study the effect of deformation on the TL, a load was dropped on to the sample with different impact velocities. TL intensity of both the peaks decreases when the TL glow curve is recorded after deforming the irradiated samples. TL emission spectrum and photoluminescence (PL) study on the sample show two prominent peaks around 480 and 550 nm due to D-5(4) -> F-7(6) and D-5(4) -> F-7(5) transitions of Tb3+ ions. It is suggested that the recombination of electrons released from the traps during the thermal excitation is responsible for the luminescence in this system and the deformation of sample damages the traps centers which reduces the TL intensity of the sample.