The Study of Structural Disorder in Spinel by ALCHEMI

Abstract

The mineral spinel (MgAl2O4) is a candidate material for proposed fusion reactors because of its resistance to structural damage during irradiation. When irradiated to high damage levels, spinel is eventually driven amorphous. However, at lower fluences the nearly cubic close packed arrangement of the oxygen anions remains intact, as indicated by electron diffraction patterns consistent with a face centered cubic Bravais lattice. in this regime, the damage to the material is manifested primarily in the redistribution of the magnesium and aluminum cations among the interstices of the anion sublattice. For ion irradiation, the study of these early stages of damage is well suited to electron beam characterization methods, because the damage is spatially localized at the nearsurface region. Electron diffraction methods have been used for the characterization of cation disorder, but are notoriously unreliable because the similarity in the elastic scattering cross sections offers little discrimination between the magnesium and aluminum cations.