Pressure-Induced Order-Disorder Phase Transition of Spinel Single Crystals

The present study deals with single-crystal structure investigations by means of X-ray scattering of a pressure-induced phase transition of Mg_0.4Al_2.4O₄. The compressibility of the substance is very small, whereas the structural changes are surprisingly high. A non-identified high-pressure phase turns out to be reversible considering the existence of a spinel single crystal, but not reversible with regard to the ordering of the cations in the oxygen framework. The pressure-induced disordering of the cations is preserved on abrupt pressure decrease and can be detected in a recovered specimen.