Stability of Wadsley-type vanadium oxides V2O5 and V6O13 at high pressures

A simple method to grow single crystals of α-V2O5 is presented and discussed. Crystal structures of two Wadsley phases, α-V2O5 (Pmmn, Z = 2) and α-V6O13 (C2/m, Z = 2), are studied with single-crystal X-ray diffraction in diamond anvil cells up to 12.8 GPa and 9.4 GPa, respectively, at room temperature. α-V2O5 irreversibly amorphizes above about 7.3 GPa. No phase transition is observed at lower pressures. The polymorph that crystallizes from the amorphous material at high pressures and high temperatures is δ-V2O5 (C2/c, Z = 4) as evidenced by in-situ angle-dispersive synchrotron powder diffraction using large-volume multi-anvil press. No phase transitions were observed during high temperature decompression of the as synthesized δ-V2O5. The crystal structure of α-V6O13 is stable up to at least 9.4 GPa. Present data could be used to achieve better understanding of the high-pressure behavior of related Wadsley phases.