Compressional and shear-wave velocities of the polycrystallineCaGeO3perovskite to10GPa

Abstract

Compressional and shear-wave velocities and unit-cell volumes of orthorhombic $\mathrm{Ca}\mathrm{Ge}{\mathrm{O}}_{3}$ perovskite have been measured up to $10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ at ambient temperature using ultrasonic interferometry in conjunction with synchrotron x radiation. Fitting all velocity and unit-cell volume data to finite-strain equations yields the zero-pressure adiabatic bulk and shear moduli and their pressure derivatives ${K}_{S0}=194.6$ $(11)\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, ${G}_{0}=109.5$ $(5)\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$, $K_{S0}{}^{\ensuremath{'}}=6.4$ (2), $G_{0}{}^{\ensuremath{'}}=1.7$ (1), with an rms misfit of $0.009\phantom{\rule{0.3em}{0ex}}\mathrm{km}\phantom{\rule{0.2em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. From the data in the current study, we have observed no discontinuities or elasticity softening for either the bulk or shear moduli up to the peak pressure of $10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$.