Influence of the dopants and of the microstructure on the ionic conductivity of zirconia

Abstract
The electrical conductivity of monocristalline and polycristalline samples of yttria-doped zirconia was measured by impedance spectroscopy, in the temperature range 300-900°C and for oxygen partial pressures included between 10^-24 and one atmosphere. Results show that the bulk conductivity is independent of the PO₂ and varies with the amount of yttrium. The higher conductivities are obtained with zirconia samples doped with 9.5 moles %. According to recent literature oxygen diffusion data, the results have been analysed taking into account the participation of different kinds of defects to the transport processes. The grain boundary conductivity and the "composite effect" have been analysed taking into account microstructural characterizations. A maximum of ionic conductivity is observed with zirconia doped with 9.9 moles % yttrium when the amount of alumina is equal to approximatively 2 moles %.