SPECTROSCOPIC EVIDENCE OF PRESSURE-INDUCED AMORPHIZATION IN ALPHA-NAVO3

Raman spectra of alpha-NaVO3 were recorded under pressures up to 170 k bar at room temperature. A crystalline-amorphous phase transition was found at similar to 61 kbar, much lower than the pressures of other io nic materials. This transition is marked by the sudden appearance of v ery broad bands at the 800- and 350-cm(-1) regions. The amorphization involves the complete breaking up of the infinite chains of corner-lin ked tetrahedral VO4, most likely into VO3-. On decompression, the amor phous phase transforms to another phase, probably also amorphous at si milar to 40 kbar. It reverts to the stable ambient-condition alpha pha se upon heating.