Estimation of Beta Alumina Breakage by Calcium Impurities on Sodium-Sulfur Battery

Breakage of beta alumina, that was used as solid electrolyte of sodium-sulfur (NAS) battery, by calcium impurities was evaluated. The Breakage generated from the inner surface of beta alumina tube. A hetero-phase of calcium oxide was observed at the beginning point and the oxide was compound of calcium, sodium and aluminum. The inner surface made oxygen defect part by contacting with sodium and calcium reached this oxygen defect and form the hetero-phase on charging. This caused a deterioration of strength by develop inside the beta alumina and breakage.