Effects of calcium impurity on phase relationship, ionic conductivity and microstructure of Na+- β/βaEuro3-alumina solid electrolyte

Ca-doped Na+- beta/beta('')-alumina was synthesized using a solid-state reaction. The changes in the properties of Na+- beta/beta('')-alumina resulting from the presence of Ca impurity were studied. Ca (0-5 wt%) was added to the respective samples, which were then sintered. The specimens were characterized using X-ray diffraction, scanning electron microscopy, densimetry and impedance analysis. In the sintered specimens, the beta('')-alumina phase fraction decreased as Ca content increased, whereas the relative sintered density increased. The surface morphology of Ca-doped Na+- beta/beta('')-alumina specimens showed a Ca-rich layer, which was the main cause of increase in the specific resistance.