Influence of oxygen fugacity on the electrical conductivity of hydrous olivine: Implications for the mechanism of conduction

Various mechanisms of hydrogen-assisted electrical conductivity predict different dependence of conductivity on oxygen fugacity. If a majority of hydrogen-related defects (i.e., two protons at M-site) carries the electrical current, then the conductivity will be independent of oxygen fugacity, whereas if a minority defect such as free proton carries the electrical conductivity, then the electrical conductivity will decrease with oxygen fugacity. We have determined the dependence of hydrogen-assisted electrical conductivity on oxygen fugacity in hydrous olivine. We found that the hydrogen-assisted electrical conductivity in olivine decreases with oxygen fugacity. This result supports a model where hydrogen-related defect with minor concentration (e.g., free proton or one hydrogen at M-site) carries most of the electric charge.