Misfit accommodation mechanisms at moving reaction fronts during topotaxial spinel-forming thin-film solid-state reactions: A high-resolution transmission electron microscopy study of five spinels of different misfits

Abstract

Abstract Thin films of five different spinels MgAl2O4, MgCr2O4, MgIn2O4, TiMg2O4 and MgFe2O4 were grown by topotaxial solid state reactions on MgO(001) substrates. The spinels widely differed in their lattice parameter resulting in a variation in sign and amount of lattice misfit to the substrate. The films were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy/selected-area electron diffraction and energy-dispersive X-ray microanalysis before the spinel-MgO reaction fronts were investigated in detail by cross-sectional high-resolution electron microscopy. For almost vanishing misfit (TiMg2O4-MgO and MgFe2O4-MgO) the films were exactly cube-to-cube oriented to the substrate, with the spinel-MgO reaction front completely coherent. During the reaction, a network of cation antiphase boundaries formed in these films. For non-vanishing misfit, semicoherent reaction fronts occurred, with different interfacial defects forming, depending on sign and amount of the s...