The protonic conductivity of samples which contained 10mol% of In2O3 was measured, in an atmosphere which contained H or D, by using the 4-wire alternating-current impedance technique at temperatures ranging from 623 to 1673K. In the presence of high O activities, H+/D+-isotope effects were observed below about 1100K. The ratio of proton to deuteron conduction increased as the temperature decreased, and attained a value of about 1.6 at 673K. It was demonstrated that, at low temperatures, the electrical conduction was dominated by protons. On the other hand, at high H activities, an isotope effect was observed at temperatures of up to about 1600K and it was concluded that protons predominated below this temperature. Above this temperature, the isotope effect vanished, and the electrical conductivities were independent of the gas potentials. It was concluded that the electrical conductivity above 1600K was dominated by oxide ions. The activation energies were estimated to be equal to 0.74, 0.70 and 2.5eV for protons, deuterons and oxide ion vacancies, respectively.

N.Kurita, N.Fukatsu, K.Ito, T.Ohashi: Journal of the Electrochemical Society, 1995, 142[5], 1552-9