DEFECTS IN SAPPHIRE-MN INDUCED BY NEUTRON-IRRADIATION

After neutron irradiation, some impurity ions changed their valence st ates, 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) m easurements were used to determine the defects in Sapphire: Mn irradia ted by fast neutron of 2 MeV average energy and thermal neutron of 0.0 23 eV. The results of TL show that before irradiation peaks of 171 deg rees C, 259 degrees C, 320 degrees C, 350.2 degrees C and 408 degrees C all belong to the intrinsic crystal, the peak of 196 degrees C is in duced by impurity ion of Mn. After neutron irradiation, the peaks all moved to higher temperature, but got different shifts and produced a n ew peak of 154 degrees C. The shift of peak 196 degrees C is about 30 degrees C, It is explained that Mn ion aggregated with a nearest defec t and formed a cluster, which corresponding to EPR results might be Mn 2+-F cluster and the nearest defect might be F type center. The mechan ism of other shifts and another peak are also discussed in the paper. (C) 1998 Elsevier Science B.V. All rights reserved.