Structural and Vibrational Study of CsSbGeO, a New Germanate in the SbGeO Family ( = Alkali Metal).

The germanate CsSbGeO, grown spontaneously via the high-temperature solution method from CsMoO used as a flux, crystallizes in the orthorhombic system with = 12.3636(2), = 13.8521(2), = 31.

High-temperature elastic moduli of flux-grown α-GeO2 single crystal.

From high-precision Brillouin spectroscopy measurements, six elastic constants (C11, C33, C44, C66, C12, and C14) of a flux-grown GeO2 single crystal with the α-quartz-like structure are obtained in the 298-1273 K temperature range. High-temperature powder X-ray diffraction data is collected to determine the temperature dependence of the lattice parameters and the volume thermal expansion coefficients. The temperature dependence of the mass density, ρ, is evaluated and used to estimate the thermal dependence of its refractive indices (ordinary and extraordinary), according to the Lorentz-Lorenz equation.

Vibrational origin of the thermal stability in the highly distorted α-quartz-type material GeO2: an experimental and theoretical study.

We report an experimental and theoretical vibrational study of the high-performance piezoelectric GeO2 material. Polarized and variable-temperature Raman spectroscopic measurements on high-quality, water-free, flux-grown α-quartz GeO2 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-GeO2 one of the most promising piezoelectric materials for extreme temperature applications, is found to originate from the absence of a libration mode of the GeO4 tetrahedra.