Elasticity of aluminate, titanate, stannate and germanate compounds with the perovskite structure

Abstract

Ultrasonic data for the velocities of a large number of perovskite-structure compounds have been determined as a a function of pressure to 6 kbar at room temperature for polycrystalline specimens hot-pressed at pressures up to 100 kbar in solid-media devices: ScAlO 3, GdAlO 3, SmAlO 3, EuAlO 3, YAlO 3, CdTiO 3, CdSnO 3, CaSnO 3 and CaGeO 3. The elasticity data for these orthorhombic and cubic perovskites define systematic patterns on bulk modulus ( K S)-volume ( V O) and bulk sound velocity ( υ φ —mean atomic weight ( M) diagrams which are insensitiv to the details of cation chemistry and crystallographic structure. These isostructural trends are used to estimate K S = 2.5 ± 0.3 Mbar and υ φ = 7.9 ± 0.4 km/s for the perovskite polymorph of MgSiO 3. On a Birch diagram of veloc vs. density, the perovskite data define linear trends which lead to erroneous estimates of velocity for MgSiO 3 unless specific account is taken of ionic radius effects in isomorphic substitutions.