Anisotropy of electrical conductivity in dry olivine

Abstract

The electrical conductivity (σ) was measured for a single crystal of San Carlos olivine (Fo 89.1 ) for all three principal orientations over oxygen fugacities 10 −7 < < 10 1 Pa at 1100, 1200, and 1300°C. Fe‐doped Pt electrodes were used in conjunction with a conservative range of T, and time to reduce Fe loss resulting in data that is ∼0.15 log units higher in conductivity than previous studies. At 1200°C and = 10 −1 Pa, σ [100] = 10 −2.27 S/m, σ [010] = 10 −2.49 S/m, σ [001] = 10 −2.40 S/m. The dependences of σ on T and have been simultaneously modeled with undifferentiated mixed conduction of small polarons and Mg vacancies to obtain steady‐state activation energies: Ea [100] = 0.32 eV, Ea [010] = 0.56 eV, Ea [001] = 0.71 eV. A single crystal of dry olivine would provide a maximum of ∼10 0.4 S/m azimuthal σ contrast for T < 1500°C. The anisotropic results are combined to create an isotropic model with Ea = 0.53 eV.