Thermoluminescence of a lithium aluminium rich beta quartz for dosimetry purposes

A member of the beta-quartz series (Li0.73Al0.73Si1.27O4) was synthesised using the ceramic method from precursor powders - Li2CO3, Al(NO3)(3 .)9H(2)O, Si(C2H5O)(4) - with identical composition. Crystallisation of the gel was obtained by heating the raw material at 800 degrees C for 12 h. The XRD pattern of the synthetic sample indicates a beta-quartz structure with hexagonal symmetry. Thermoluminescence (TL) signals of annealed samples at 1200 degrees C for 12 h, and non-annealed samples, were measured in the UV blue region of the spectrum. The non-annealed irradiated beta-quartz displays two TL peaks at 110 degrees C and 280 degrees C which, after different additional radiation doses (from 0.4 to 5 Gy), display high linearity. The other annealed irradiated aliquots show a similar behaviour and stronger linearity. Thermal treatments at high temperature (1200 degrees C) produce ionic self-diffusion and loss of lithium atoms through the open hexagonal channel of the beta-quartz structure. These [AlO4/Li+](o) defects are responsible for the high radiation sensitivity of the sample.