Electrical conductivity of FeTiO3 ilmenite at high temperature and high pressure

Electrical conductivity measurements were carried out on synthetic FeTiO3 ilmenite with a KAWAI-type multianvil high-pressure apparatus (USSA-5000). The temperature range was 300-600 K and the pressure range was 8-16 GPa. The activation energy and the activation volume were calculated to be 0.21 eV and -0.22 cm(3)/mol, respectively. The low value of the activation energy and the small negative activation volume are consistent with conduction by hopping of small polarons, suggested to be an intervalence charge transfer Fe2++Ti4+-> Fe3++Ti3+. In comparison with the electrical conductivity of (Mg-0.93,Fe-0.07)SiO3 ilmenite with a larger activation volume of -0.90 cm(3)/mol, we suggest that Fe2+-> Fe3+ hopping conduction is the dominant conduction mechanism in (Mg,Fe)SiO3 ilmenite and significant lattice disorder was involved at high temperature.