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

Abstract

Corundum (α‐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 α‐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.

Paramagnetic Defects and Thermoluminescence in Irradiated Nanostructured Monoclinic Zirconium Dioxide

“…It is well known that an alternative mechanism for annealing radiation-induced F -type defects in oxides is the recombination of oxygen vacancies with interstitial oxygen, the diffusion of which becomes possible when the crystal is heated [ 48 , 49 , 50 ]. Previously, the authors of [ 51 ] showed that in zirconium oxide irradiated with neutrons (E > 0.1 MeV), the diffusion of interstitial oxygen becomes possible at temperatures above 500–600 K. In the samples studied by us, a decrease in the concentration of F + centers is observed at lower temperatures of 375–550 K, which testifies in favor of the proposed mechanism for the destruction of F + centers associated with their ability to capture the charge carriers released from traps that cause TL peaks.…”

Defect‐Induced Effects in Nanomaterials

“…E. Kotomin et al, V. Gusakov et al, and R. Maji et al used ab initio calculations to describe the thermal stability and recombination kinetics of primary anion Frenkel defects À the F and F þ electronic centres and oxygen interstitials À in fast-neutronirradiated α-Al 2 O 3 single crystals, [1] formation and diffusion of intrinsic defects in bulk and monolayer MoS 2 , [2] and the interaction of grain boundaries (GB) with inherent defects and/or impurity elements in multi-crystalline Si, [3] respectively. The co-existence of two types of interstitialsneutral O atoms and negatively charged O ionsin α-Al 2 O 3 has been demonstrated for the first time.…”