Solid-state amorphization of a quenched high-pressure GaSb phase studied by real-time neutron diffraction: evolution of the crystalline phase.

The amorphization of a quenched sample of the GaSb-II high-pressure phase was studied at ambient pressure by real-time neutron diffraction in the course of the sample heating from 100 K to room temperature at a rate of 0.4 K min(-1). The transformation to the amorphous state begins at 140 K and is completed near room temperature. The ß-Sn type structure was shown to represent only the mean lattice of the high-pressure GaSb-II phase. The superstructure of this phase widely varied with temperature and is caused by the ordered displacement of atoms. The temperature range of the metastable crystalline phase relaxation is divided into three intervals according to the temperature dependence of the tetragonality ratio (c/a). At the boundaries of these temperature intervals, i.e. temperatures T = 170 and 230 K, two second-order phase transitions are observed. Anomalous heat and volumetric effects were observed earlier by means of calorimetry and dilatometry in the same temperature range. Variation of the ß-Sn type crystal structure reflects the general tendency of ideal tetrahedral bond network recovery. All phase transformations observed were found to be irreversible.