CHANGE IN PROPERTIES OF BETA''-ALUMINA AFTER NA S CELL TEST

Changes in characteristics of beta"-alumina subjected to long term Na/S cell tests were investigated by diametralstrength measurement,micro-Vickers hardness measurement,X-ray diffraction, EDX analysis and SIMS analysis. Degraded layers were observed at the sulfur side of beta"-alumina as well as at the sodium side, which had been reported before, after the charge transfer (charge+discharge) of 2022 Ahcm-2, while the sulfur side was unaffected by the charge transfer of 810 Ahcm-2. Micro-Vickers hardnesses in both the degraded layers were lowered, compared to those before the cell test. The half-width of X-ray diffraction lines of the sulfur side of beta"-alumina was broadened by the charge-discharge cycling, but those of the sodium side did not change. The concentration of potassium was also observed at the sulfur side of beta"-alumina. These facts suggest that the degradation at the sulfur side of beta"-alumina is caused by defects in beta"-alumina grains which the concentration of potassium would bring.