Pressure-induced phase transitions of Zn2SiO4 III and IV studied using in-situ Raman spectroscopy

Abstract

Recent structural study of the high-pressure Zn2SiO4 phases III and IV has suggested that they are retrograde phases formed during decompression. To clarify the stabilities of these phases under pressure, in-situ high- pressure Raman spectroscopic measurements were taken at room temperature. Phase III, having a 'tetrahedral olivine' structure, transformed to a new phase at 5.5 GPa during compression and returned to phase III at 1.7 GPa during decompression. Phase IV also exhibited a phase transition at 2.5 GPa with very small hysteresis. Both transitions are first-order. These observations confirmed that phases III and IV are retrograde phases.