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

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.

Atomic, electronic and magnetic structure of an oxygen interstitial in neutron-irradiated Al2O3 single crystals

“…[43][44][45][46][47][48][49][50] and references therein). Also, a neutron-irradiated magnesium aluminate spinel (MgAl 2 O 4 ) demonstrated the presence of V-type defects, which was confirmed by experimental EPR studies [51][52][53] and following theoretical considerations 54 . The latter theoretical study was the first attempt of hyperfine coupling constants calculations using the first-principles methods for MgAl 2 O 4 spinel, and to the best of our knowledge, other oxides.…”

“…A special attention is paid to the comparative investigation and analysis of the thermal annealing of the EPR signals of and F + centers and the corresponding absorption bands induced by fast fission neutrons. This is a logical continuation of our study on the V -type defects in neutron irradiated MgAl 2 O 4 combining the EPR, optical methods 51 – 53 and DFT calculations therein 54 .…”

Low-temperature studies of Cr3+ ions in natural and neutron-irradiated g-Al spinel

“…Oxide materials with a spinel structure of the general formula AB 2 O 4 (A = Mg, Zn; B = Al, Ga) demonstrate unique physicochemical properties, which determines their extensive research and growing interest in their use in various scientific and industrial applications [1][2][3][4][5][6][7][8][9]. Among all the metal oxides, magnesium aluminate spinel (MgAl 2 O 4 ), receives specific attention [1][2][3]10]. MgAl 2 O 4 is a refractory oxide material with high toughness and chemical stability, low electrical conductivity, and low density (~ 3.6 g/cc), high melting temperature (~ 2150 °C), and it is transparent in the visible and infrared wavelength regions.…”

“…MgAl 2 O 4 is a refractory oxide material with high toughness and chemical stability, low electrical conductivity, and low density (~ 3.6 g/cc), high melting temperature (~ 2150 °C), and it is transparent in the visible and infrared wavelength regions. Their attractive optical and luminescent properties, high thermal and chemical stability, as well as high resistance to radiation damage, make these compounds suitable for a very wide range of different applications, including electroluminescent and vacuum fluorescent displays, light-emitting diodes, solidstate lasers, UV photodetectors, as well as optically-stimulated storage and long persistent phosphors, IR windows as well as functional optical and dielectric materials for nuclear fusion reactor applications [9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Ceramic MgAl 2 O 4 materials are also planned to be exploited as a porous material for different sensor applications, such as humidity control [24][25][26][27].…”

“…Note, that corresponding detailed studies of the structure and phase transformations in natural and synthetic crystals of magnesium-aluminum spinel containing transition metal ions (Cr 3+ , Mn 2+ ) were carried out after irradiation with fast neutrons [32,33]. In addition, using EPR, optical absorption, and cathodoluminescence, intrinsic structural radiation defects and their thermal annealing in stoichiometric MgAl 2 O 4 single crystals and nonstoichiometric MgO•2.5Al 2 O 3 irradiated with fast neutrons have been studied in detail [10,13,14,[34][35][36].…”