Thermal conductivity of CaGeO3 perovskite at high pressure

Abstract

The pressure dependence of thermal conductivity (K) in Earth's lower mantle is poorly understood, resulting in very uncertain K values in the D. Using orthorhombic CaGeO3 perovskite as an analogue for MgSiO3 perovskite, we measured K in a multi-anvil apparatus using the ngstrm method at pressures of 8, 10, 14 and 18 GPa, and temperatures of 573-1073 K. We find the pressure dependence of thermal conductivity for orthorhombic perovskite shows a somewhat higher slope than that predicted by Debye theory, and account for this by relating phonon velocities to the bulk modulus, rather than to the Debye temperature. From this relation, we estimate the thermal conductivity of MgSiO3 perovskite at the top and bottom of the D to be 3.3 W/m K and 2.2 W/m K, corresponding to values of 6.4 W/m K and 4.5 W/m K for the mantle. Copyright 2011 by the American Geophysical Union.