The temperature dependence of the production efficiency of irradiation-induced defects in neutron-irradiated oxides was investigated. Some oxide single crystals, MgO, α-Al2O3 (sapphire) and TiO2 (rutile), were irradiated at 10, 20, 50, 100, 150 or 200K by using a low-temperature irradiation facility, and at ambient temperature (about 370K) in the same facility. The irradiation-temperature dependence of the production efficiency of a 1μm band in TiO2 differed greatly from that of anion vacancy (F-type centers) in MgO and α-Al2O3. The results for MgO and α-Al2O3 exhibited steep negative gradients from 10 to 370K, whereas that for TiO2 included a valley between 40 and 60K and a hump at about 130K, and then disappeared at about 200K. In MgO and α-Al2O3, this behavior could be explained by the recombination of Frenkel pairs, which was activated at higher temperatures. In TiO2, in addition to the recombination mechanism, a covalent bonding property was thought to exert a strong influence, and it was suggested that disappearance of the 1μm band at above 200K was due to the recombination process of Frenkel pairs which was caused by the irradiation-induced crystallization.

Irradiation Temperature Dependence of Production Efficiency of Lattice Defects in Some Neutron-Irradiated Oxides. Okada, M., Atobe, K., Nakagawa, M.: Nuclear Instruments and Methods in Physics Research Section B, 2004, 226[3], 369-75