Pressure-induced phase transitions in chromium thiospinels - art. no. 064106

The pressure and temperature dependence of the structure of CoCr2S4 and Co0 .65Ni0.35Cr2S4 have been studied by in situ time-of-flight powder neutron d iffraction. While the thiospinel CoCr2S4 transforms to a defect NiAs-type p hase at 1.3 GPa and 800 degreesC, the nickel-doped thiospinel undergoes thi s phase change at 0.4 GPa and 750 degreesC. Quenching of the hexagonal high -temperature and high-pressure phase resulted in a transition to a monoclin ic Cr3S4 phase, due to the ordering of the metal vacancies in every second layer. Moreover, the spinel CoCr2S4 transforms at room temperature and 8.6 GPa to a phase which does not exhibit a NiAs-type structure.