Pressure-induced amorphization and decomposition inZrV2O7: A Raman spectroscopic study

Abstract

In situ high-pressure Raman spectroscopic studies on $\mathrm{Zr}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$ suggest growth of disorder in the high-pressure orthorhombic phase, inferred from the excessive broadening of Raman peaks, and the sample gradually turns amorphous above $4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. The samples pressure cycled from $10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ exhibit irreversible amorphization. On the other hand, the spectrum of the sample pressure cycled from $4\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ is found to have all the characteristic peaks of ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$ indicating a possible decomposition of the compound into a mixture of simple oxides. A partial decomposition is indeed confirmed from the x-ray-diffraction pattern of the recovered sample. A large decrease of the intensity of the $\mathrm{V}{\mathrm{O}}_{4}$ tetrahedral stretching modes is consistent with the possible coordination change of vanadium, from fourfold in $\mathrm{Zr}{\mathrm{V}}_{2}{\mathrm{O}}_{7}$ to fivefold in ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$. Nucleation of nano-/poorly crystallized grains of the daughter phase even at ambient temperature is understood as due to the existence of the fivefold coordinated crystalline phase, ${\mathrm{V}}_{2}{\mathrm{O}}_{5}$.