Electronic Transport in 8 Mole Percent  Y 2 O 3 ‐ 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 (800°–1050°C) and p O 2 (0.21–10 −17 atm). Ionic conductivity was measured by the conventional four‐probe method. The following empirical equations were derived for the ion, electron, and hole conductivities, in ohm −1 cm −1 σ ion = 1.63 × 10 2 exp − 0.79 eV / kT σ e = 1.31 × 10 7 exp − 3.88 eV / kT p O 2 − 1 / 4 σ h = 2.35 × 10 2 exp − 1.67 eV / kT p O 2 + 1 / 4 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 as follows For holes D h = 0.23 exp − 1.15 eV / kT μ h = 0.85 exp − 1.05 eV / kT For electrons D e = 2.30 × 10 2 exp − 2.00 eV / kT μ e = 8.02 × 10 2 exp − 1.89 eV / kT 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.