Pressure-induced structural instability and amorphization in compressed α-V2O5

We report pressure-induced structural instability and amorphization in compressed orthorhombic alpha-V2O5 by in situ synchrotron x-ray diffraction observations and Raman spectroscopy measurements in diamond-anvil cells up to 20.2 GPa and 21.9 GPa, respectively. In situ x-ray lattice parameters (a, b, c) and d-spacings at high pressure show that the orthorhombic alpha-V2O5 exhibits an apparent discontinuity at -4.3 GPa, indicating the occurrence of structural distortion upon compression. Upon further pressurization, the distorted alpha-V2O5 starts to be amorphizing at -12.6 GPa and becomes fully amorphous at -20.2 GPa, which is again confirmed by our high-pressure Raman spectroscopy measurements. This obtained amorphous V 2 0 5 polymorph can be recovered at ambient conditions, showing that the pressure-driven distorted orthorhombic-to-amorphous phase transformation is irreversible. Moreover, Gruneisen parameters of various Raman modes for alpha-V2O5 are derived, which are in agreement with the previously experiential study by Arora et al. Our results might be important to understand the highpressure behaviors in M2O5 polymorphs for their uses at extreme conditions. (C) 2019 Elsevier B.V. All rights reserved.