PRESSURE-INDUCED PHASE-TRANSITION IN FERRIELECTRIC CUINP2S6

We report the first observation of a pressure-induced phase transition in a lamellar chalcogenophosphate. Raman scattering measurements on t he layered ferrielectric CuInP2S6 were performed at pressures of up to 17.5 GPa and room temperature. The recorded spectra indicate the onse t of a transition at about 4.0 GPa which is inferred to be first-order . The significantly reduced number of bands observed at high pressure and reversibility of the transition are consistent with the conservati on of the lamellar morphology and a possible ABC to AB chalcogen stack ing change. A discussion is given of how compression might modify the potential for the off-center cations and the polar state of this mater ial. (C) 1998 Elsevier Science Ltd. All rights reserved.