中国科学院地球化学研究所机构知识库

The electrical conductivity of dry polycrystalline olivine compacts (hot-pressed and sintered pellets) was measured at pressures of 1.0-4.0 GPa, at temperatures of 1073-1423 K, and at different oxygen fugacities via the use of a YJ-3000t multi-anvil press. Oxygen fugacity was controlled successfully by means of five solid buffers: Fe3O4-Fe2O3, Ni-NiO, Fe-Fe3O4, Fe-FeO and Mo-MoO2. Within the selected frequency range of 10(2)-10(6) Hz, the experimental results indicate that the grain interior conduction mechanism is characterized by a semi-circular curve on an impedance diagram. As a function of increasing pressure, the electrical conductivity of polycrystalline olivine compacts decreases, whereas the activation enthalpy and the temperature-independent pre-exponential factors increase slightly. The activation energy and activation volume of polycrystalline olivine compacts were determined to be 141.02 +/- 2.53 ki/mol and 0.25 +/- 0.05 cm(3)/mol, respectively. At a pressure of 4.0 GPa, electrical conductivity was observed to increase as a function of increasing oxygen fugacity, and the relationship between electrical conductivity and oxygen fugacity can be described as log(10) (sigma) = (2.47 +/- 0.085) + (0.096 +/- 0.023) x log(10) f(O2). + (-0.55 +/- 0.011)/T, which presents the exponential factor q (similar to 0.096). Our observations demonstrate that the primary conduction mechanism for polycrystalline olivine compacts is a small polaron.