Effect of pre-thermal treatment on the OSL response of Al2O3:Si,Ti

We have recently reported optically stimulated luminescence (OSL) characteristics of the Al2O3:Si,Ti phosphor along with some thermoluminescence (TL) and photoluminescence (PL) studies, The TL glow curve of this phosphor shows peaks around 158, 191, 276 and 355 degrees C for a heating rate of 4 Ks(-1). In order to investigate the contribution of individual TL traps to OSL signal, CW-OSL was studied as a function of pre-thermal treatment in the temperature range 27-450 degrees C. The integrated CW-OSL intensity of the phosphor remains constant up to 100 degrees C; beyond this temperature the integrated intensity goes oil decreasing with increase in temperature. After a pre-thermal treatment at 225 degrees C the CW-OSL intensity falls by 73% of its initial value. Hence, it can be concluded that the TL traps up to 225 degrees C are responsible for the major contribution to the CW-OSL signal in this phosphor. The OSL indicates that all the TL traps, up to 400 degrees C, give measurable contribution to the OSL signal. The OSL signal becomes insignificant when the exposed phosphor is annealed beyond 400 degrees C. It decreases nearly to zero for the sample annealed at 400 degrees C as compared to the OSL intensity of the sample without any pre-thermal treatment. Optical bleaching results indicate that all the TL peaks decrease continuously as a function of bleaching time.