Electronic transport in 8 mole percent Y2O3-ZrO2

By means of a gas-tight electrochemical cell, oxygen permeation measurements have been performed on the oxygen ion conductor 8 mole percent (m/o) yttria-stabilized zirconia, as a function of T (8000-10500C) and ρO2 (0.21-10-17 atm). Ionic conductivity was measured by the conventional four-probe method. The empirical equations derived for the ion, electron, and hole conductivities, in ohm-1cm-1 are presented. The electronic diffusivity, D, and mobility, μ, for holes and electrons were determined by nonsteady-state oxygen permeation measurements. A gas-switching method was employed. Results indicate that the holes and electrons move by a thermally activated hopping-type mechanism. The equations for D and μ are given. The electronic semiconducting properties obey Boltzmann-type statistics at temperatures investigated. An analysis was carried out by combining results from electronic transport and solid-state coulometric titration measurements under the assumption of trapping of electrons and holes on the appropriate sublattices. The results indicate that the transport of electrons and holes is due to a thermal excitation process and that electrons and holes are trapped on the appropriate sublattices