Determination of thermoluminescence properties of ZnBO:Tm,Li for dosimetric purposes.

This study aims to investigate the comparison of the thermoluminescence (TL) emission of Li and Tm co-doped and un-doped zinc borate (ZnBO) phosphors prepared by wet chemical synthesis method. The crystal structure of the samples has been determined by means of X-ray powder diffraction and matched with the standard pattern of ZnBO (PDF Card No. 039-1126). TL glow curves of 5 Gy beta irradiated Li (at different concentrations of 0.2, 0.5, 0.8 and 1.0%) and Tm (1.0%) co-doped ZnBO have been recorded using various band pass filters to determine both the optimum concentration and the suitable filter. The TL green emission (565 nm) of Li (1.0%), Tm (1.0%) co-doped ZnBO phosphor displays a complex structure where one can distinguish, at least, three groups of components peaked at 69, 166 and 291 °C where the more suitable dosimetric maxima appears at higher temperature. It could be observed how the 166 and 291 °C TL glow maxima of this material exhibits (i) good linearity in the range of 0.11-15 Gy, (ii) a minimum detectable dose value of 1.11 mGy, (iii) does not modify significantly the TL emission in shape and intensity after reusability (10 cycles) and (iv) a negligible fading effect for 5 Gy irradiated aliquots stored in darkness and room temperature up to 169 h. Additionally, it could be found that (v) kinetic parameters estimated by using variable heating rate method of Hoogenstraaten and initial rise method give similar results.