Comparison of the High Pressure Structures of Spinel Single Crystals with Composition Mg_{0. 4}Al_{2. 4}O₄ and ZnCr₂S₄

抄録

The present study deals with single crystal structure investigations of Mg _{0. 4}Al_{2. 4}O₄ and ZnCr₂S₄ by means of X ray scattering. The compressibility of the oxide substance is very small, whereas the structural changes are surprisingly high. In contrast, the compressibility of the thiospinel is 3 times higher, but the structural changes are very small. The transition to a non-detectable high pressure phase of Mg_{0. 4}Al_{2. 4}O₄ turns out to be reversible considering the existence of a spinel single crystal, but not reversible concerning the values of the lattice constant and the positional parameter of the oxygen anion. This can be explained by pressure induced disordering of the cations, which is preserved on abrupt pressure decrease.