Oxygen ionic conduction in MgSiO3 perovskite

The electrical conductivity of Na-doped MgSiO(3) perovskites has been measured at 24 GPa and temperatures between 1300 and 2200 K. At temperatures below about 1800 K extrinsic oxygen ionic conduction dominates, with an activation energy of 1.4 +/- 0.2 eV and a pre-exponential which is proportional to the Na-content. At higher temperatures, a different conduction mechanism, which is insensitive to Na-content, dominates with DeltaH = 3.6 +/- 0.2 eV and log sigma(0) = 9.4 +/- 0.4 S m(-1). This is tentatively attributed to intrinsic electronic conduction. The present results suggest that there may be a region at the top of the earth's lower mantle in which the electrical conductivity is particularly sensitive to compositional effects. Deeper still, the earth's electrical conductivity will be more sensitive to temperature effects. (C) 2003 Elsevier B.V. All rights reserved.