Vibrational origin of the thermal stability in the highly distorted α-quartz-type material GeO_2: An experimental and theoretical study

摘要

We report an experimental and theoretical vibrational study of the high-performance piezoelectric GeO_2 material. Polarized and variable-temperature Raman spectroscopic measurements on high-quality, water-free, flux-grown α-quartz GeO_2 single crystals combined with state-of-the-art first-principles calculations allow the controversies on the mode symmetry assignment to be solved, the nature of the vibrations to be described in detail, and the origin of the high thermal stability of this material to be explained. The low-degree of dynamic disorder at high-temperature, which makes α-GeO_2 one of the most promising piezoelectric materials for extreme temperature applications, is found to originate from the absence of a libration mode of the GeO_4 tetrahedra.