High-pressure raman study of CsVO₃ and pressure-induced phase transitions

Abstract

The pressure dependence of the Raman frequencies of cesium vanadate (CsVO₃) was studied using a diamond anvil cell up to 15 GPa. From the abrupt changes in the Raman specta three pressure-induced phase transitions are inferred at 10, 11.5 and 13 GPa. The first phase transition, at 10 GPa, is subtle but affects the VO bond length. It is believed that this transition is of the same nature as that observed in postassium and rubidium vanadates. The much higher transformation pressure in CsVO₃ is attributed to the anomalous compressibility of the Cs⁺ ion. The second phase transition involves more drastic changes in the high-frequency region. This is attributed to the rotations and distortions in the VO₄ tetrahedra which lower the symmetry of the lattice. In the third phase transition, the appearance of broader Raman peaks and the disappearance of the chain deformation modes suggest a partial disorder in the chain structure.