Pressure-induced amorphization in α-GeO2: Structural evolution and improved dielectric properties

In this paper, we report the investigation of the structure evolution and dielectric properties of α-GeO₂ under compression using in-situ Raman spectroscopic measurements, alternate current impedance spectroscopic measurements, and first-principal calculations. It is discovered that the coordination number of Ge in α-GeO₂ increases from 4 to 6 at 5.0 GPa, while an amorphous state forms at 11.5 GPa and maintains to ambient conditions. The alternate current impedance spectroscopy measurements revealed that the variation of electrical resistance shows opposite tendencies at pressures against that of the coordination number. This phenomenon is ascribed to the pressure-induced emergence of unbonded oxygen atoms, and thus the increase of the concentration of oxygen ions in the GeO₄ tetrahedra. Meanwhile，it is found that the application of pressure-induced amorphization improves the dielectric properties to a certain extent, which is of significant importance to provide a valuable approach for the synthesis of amorphous oxides with better dielectric properties.