The Two Types of Oxygen Interstitials in Neutron-Irradiated Corundum Single Crystals: Joint Experimental and Theoretical Study

Corundum (alpha-Al2O3) is a technologically important material and, in particular, widely used in optical applications such as luminescent radiation dosimeters, cryogenic scintillators, and is being considered as a promising candidate for windows in future fusion reactors. Its optical and mechanical properties are controlled by the presence of radiation-induced (in particular, by fast neutrons) defects. Herein, the thermal stability and recombination kinetics of primary anion Frenkel defects-the F and F+ electronic centers and oxygen interstitials-in fast-neutron-irradiated alpha-Al2O3 single crystals are analyzed. Theory is developed considering the formation of both neutral and charged oxygen Frenkel defect pairs; defect migration, interaction and recombination. Based on ab initio calculations and new theoretical kinetics analysis, for the first time, a coexistence is demonstrated, in comparable concentrations, of two interstitial types-neutral O atoms and negatively charged O- ions (with attributed optical absorption band maxima at 6.5 eV and 5.6 eV, respectively); and their diffusion parameters, necessary for the prediction of secondary defect-induced reactions and defect/material thermal stability, are obtained.

Automated summary

This study analyzed the thermal stability and recombination kinetics of primary anion Frenkel defects in fast-neutron-irradiated alpha-Al2O3 single crystals, and demonstrated for the first time the coexistence of two types of oxygen interstitials. The diffusion parameters of these interstitials were obtained, which are crucial for predicting secondary defect-induced reactions and thermal stability of the material.