Influence of CuO and ZnO additions on grain growth and proton conductivity of Y-doped BaZrO3

The effect of CuO, ZnO, and CuO+ZnO sintering aids added to BaZr0.8Y0.2O3−δ was investigated on phase formation, microstructure, and proton conductivity with the use of the X-ray diffraction technique, scanning electron microscopy, and electrochemical impedance spectroscopy, respectively. The BaZr0.8Y0.2O3−δ pellet samples were prepared by the solid-state reaction method and sintered at 1400 °C for 10 h. The presence of a secondary phase was not detected by XRD in samples with sintering aids. The relative density of the samples without a sintering aid was 68%, while all samples with sintering achieved over 95%. SEM images revealed how the different types of sintering aids lead to the alteration of grain size, microstructure, and proton conductivity. Grain boundary conductivities were observed to improve with the addition of CuO+ZnO promoting abnormal grains such as plate-like grains and large equiaxed grains.