Defects in sapphire:Mn induced by neutron irradiation

After neutron irradiation, some impurity ions changed their valence states, as well as some new defects such as vacancies, interstitials and the clusters were produced. The thermoluminescence (TL) with electron paramagnetic resonance (EPR), positron annihilation technique (PAT) measurements were used to determine the defects in Sapphire:Mn irradiated by fast neutron of 2 MeV average energy and thermal neutron of 0.023 eV. The results of TL show that before irradiation peaks of 171 C, 259 C, 320 C, 350.2 C and 408 C all belong to the intrinsic crystal, the peak of 196 C is induced by impurity ion of Mn. After neutron irradiation, the peaks all moved to higher temperature, but got different shifts and produced a new peak of 154 C. The shift of peak 196 C is about 30 C. It is explained that Mn ion aggregated with a nearest defect and formed a cluster, which corresponding to EPR results might be Mn2+-F cluster and the nearest defect might be F type center. The mechanism of other shifts and another peak are also discussed in the paper. (orig.)