Distinctive features of diffusion-controlled radiation defect recombination in stoichiometric magnesium aluminate spinel single crystals and transparent polycrystalline ceramics

A. Lushchik,E. Shablonin,E. Feldbach,V. N. Kuzovkov,V. Seeman,A. I. Popov,I. Kudryavtseva,E. A. Kotomin

doi:10.1038/s41598-020-64778-8

A. Lushchik, E. Shablonin + Show 6 more

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https://doi.org/10.1038/s41598-020-64778-8

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Journal: Scientific Reports	Publication Date: May 8, 2020
Citations: 50	License type: open-access

Affiliation: University of Tartu, University of Latvia

Abstract

MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications. The kinetics of thermal annealing of the basic electron (F, F+) and hole (V) centers in stoichiometric MgAl2O4 spinel irradiated by fast neutrons and protons is analyzed in terms of diffusion-controlled bimolecular reactions. Properties of MgAl2O4 single crystals and optical polycrystalline ceramics are compared. It is demonstrated that both transparent ceramics and single crystals, as well as different types of irradiation show qualitatively similar kinetics, but the effective migration energy Ea and pre-exponent D0 are strongly correlated. Such correlation is discussed in terms of the so-called Meyer-Neldel rule known in chemical kinetics of condensed matter. The results for the irradiated spinel are compared with those for sapphire, MgO and other radiation-resistant materials.

Highlights

MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications
The formation energy of these so-called antisite defects (ADs), which are charged (-1 or +1) with respect to a regular lattice, is significantly lower than that for any other elementary lattice defects[21]. Just this circumstance explains the presence of a considerable concentration of ADs in as-grown single crystals and optical ceramics, while further irradiation even increases the degree of cation disorder, a kind of structural inversion
The functionality of optical materials/components strongly depends on the radiation damage kinetics − accumulation of radiation defects with the irradiation fluence/dose as well as their annealing via a subsequent thermal treatment of the irradiated materials

Summary

Introduction

MgAl2O4 spinel is important optical material for harsh radiation environment and other important applications. The formation energy of these so-called antisite defects (ADs), which are charged (-1 or +1) with respect to a regular lattice, is significantly lower than that for any other elementary lattice defects[21] Just this circumstance explains the presence of a considerable concentration of ADs in as-grown single crystals and optical ceramics, while further irradiation even increases the degree of cation disorder, a kind of structural inversion. The radiation effects in constituent parts of MgAl2O4 − MgO and Al2O3 binary oxides have been thoroughly studied (see[22,23,24,25,26,27,28,29,30,31,32,33,34,35] and references therein) and the results on the microstructure, creation mechanisms and annealing kinetics of Frenkel defects (interstitial-vacancy pairs) and their simplest aggregates have been extended to magnesium aluminate single crystals and optical ceramics (see, e.g.36–52). Less stable and more energetic electronic excitations (e.g., hot, non-relaxed e-h pairs63,64,66–68) could contribute to radiation damage under metal oxide irradiation with swift ions (including protons)

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