Influence of microstructure on the ionic conductivity of yttria-stabilized zirconia electrolyte

Yttria-stabilized zirconia (YSZ) electrolytes with diverse microstructures were prepared by using nano-size (Y2O3)0.08(ZrO2)0.92 powders as precursors through conventional sintering in air. The electrolytes were tested by AC impedance spectroscopy to elucidate the contribution of intragranular and intergranular conductivity to the total ionic conductivity. The intragranular conductivity and intergranular conductivity were correlated with the microstructures of the electrolyte to interpret the transportation of oxygen ions through the electrolyte. The intragranular conductivity was found to be dominated mainly by the relative density while the intergranular conductivity strongly depended on the grain size and grain boundary area of the electrolyte. The sintering temperature and isothermal time dependence of ionic conductivity reached a maximum value of 0.105 S/cm at a sintering temperature of 1350 °C for 4 h and 0.112 S/cm at a holding time of 8 h at 1250 °C when measured at 1000 °C, respectively. Concepts for improving the ionic conductivity of YSZ electrolyte were reviewed.