Influence of Co3O4 addition on the ionic conductivity and microstructural properties of yttria-stabilized zirconia (8YSZ)

Abstract

Abstract In this study, 0 – 15 wt.% Co3O4 powders were added to 8 mol.% yttria-stabilized cubic zirconia (8YSZ) powders in order to determine the effect of Co3O4 addition and amount on the microstructure, sintering, and electrical properties of yttria-stabilized cubic zirconia. Colloidal processing was used to ensure uniform mixing of the powders and to obtain a homogeneous microstructure. X-ray diffraction results showed that the average lattice parameter of the yttria-stabilized cubic zirconia decreased from 5.146 Å to 5.135 Å upon Co3O4 addition, and that the lattice parameter did not change above a Co3O4 content of 1 wt.%. The initial decrease in the lattice parameter is attributable to the smaller ionic radius of Co3+ dissolved in the yttria-stabilized cubic zirconia matrix. The electrical conductivity of the specimens was measured using a frequency response analyzer in the range of 100 mHz – 13 MHz and 300 – 800 °C. Grain boundary conductivity of yttria-stabilized cubic zirconia was found to be enhanced with increasing Co3O4 addition, with the presence of electronically conductive cobalt oxide at grain boundary triple points increasing the grain boundary conductivity, due to an increase in the Co3+ and Co2+ electronic charge carrier ions.