High-temperature electrical conductivity of FeTiO3 and ilmenite.

Resistivity measurements have been carried out on FeTiO3 and the mineral ilmenite to characterize these materials in terms of oxygen exchange in the gas phase. These measurements were obtained in the temperature range 400-1273 K and in the oxygen partial pressure range 0.5-101.3 Pa. The activation energies of conductivity were found in the range 0.10 +/- 0.01-0.40 +/- 0.01 eV for FeTiO3, and 0.13 +/- 0.01-0.21 +/- 0.01 eV for ilmenite, independent of the oxygen fugacity. FeTiO3, which behaves as p-type semiconductor, shows a sigma proportional to(P-o2)(1/n) experimental dependence with n = +4, supporting an oxygen-exchange process based mainly on the formation of singly negative metal vacancies. Under the same conditions, the resistivity measurements carried out on ilmenite indicated that the sample conductivity was independent of the oxygen partial pressure. This is to be expected if the concentrations of electrons and electron defects are much larger than those of the ionic defects. In this case, the disorder of electrons is not influenced by small deviations from ideal stoichiometry.