Correlating the TL response of γ-irradiated natural quartz to aluminum and hydroxyl point defects

This paper investigates the relationship between Al- and OH-related point defects with the thermoluminescent (TL) response of natural quartz sensitized with high doses of γ radiation and heat-treatments. For this, specimens from a single crystal were progressively irradiated with doses of 60Co from 2 to 50 kGy. After each step of sensitization, the absorption bands related to [AlO4]0, [AlO4/H]0, [H4O4]0 and Li-dependent OH point defects were measured by optical absorption and infrared (IR) spectroscopy. The sensitization of the 280 °C TL peak increased up to 15 kGy and then its intensity remained constant. The absorption intensity at 470 nm increased with γ doses suggesting a progressive creation of [AlO4]0 acting as recombination centers for the sensitized peak. At the same time, the TL intensity of the 90 °C peak decreased with the accumulated dose. This effect was not related to the saturation in the number of recombination centers because both [H4O4]0 and [AlO4]0 bands were increasing after 50 kGy. Compared to the as-received condition, it was found that IR bands associated with [AlO4/H]0 and Li-dependent OH decreased with the effect of heat-treatments. The precursor for [AlO4]0 is [AlO4/Li]0 and the Li species dislodged from [AlO4/Li]0 and Li-dependent OH centers play an important role in the sensitization process.