High-pressure amorphous phase of vanadium pentaoxide

We have discovered a high-pressure amorphous state of vanadium pentaoxide based on the results of an in situ high-pressure Raman spectroscopic and synchrotron x-ray diffraction study in a diamond-anvil cell up to 53 GPa under nonhydrostatic conditions. The broadening of Raman spectra and the diminishing of diffraction intensities suggest the evolution of disorder in the high-pressure beta phase. The compound has been found to undergo amorphization around 40 GPa. Upon the release of pressure, the material remains amorphous; however, the changes in the shapes of the structure factor and pair correlation function suggest that a-V2O5 recovered after pressure cycling is different from that at high pressure, indicating possible polyamorphism. Raman investigations show that unlike alpha and beta crystalline phases, the high-pressure amorphous phase contains only doubly coordinated oxygen. A comparison of the Raman spectrum of a-V2O5 recovered from high pressure with that of the vapor-deposited a-V2O5 film suggests that although both of these have disordered arrangements of V=O bonds, their structures are not identical.