Low-temperature sintering of sodium beta alumina ceramics using nanosized SnO2 sintering aid

Abstract

Sodium beta alumina ceramics (Na1.67Al10.67Li0.33O17) is used in sodium sulphur batteries as solid electrolyte. In the present work, sodium beta alumina powder has been synthesized by the solid state method using Al2O3, Na2CO3 and Li2CO3 as the starting materials. The effect of nanosized SnO2 additive on sintering behaviour, microstructure, mechanical and electrical properties of sodium beta alumina ceramics has been investigated. The results indicated that the addition of 1mol% of nanosized SnO2 particles, determined as the optimal amount, can decrease the sintering temperature of sodium beta alumina ceramics for about 100?C, and lead to the excellent densification and proper microstructure, as well. Improvement in sintering behaviour of beta alumina ceramics in the presence of nanosized SnO2 additive is apparently due to the formation of a liquid phase during the sintering process and lower sodium loss. The results also proved that by SnO2 addition, ionic conductivity at 300?C, fracture strength and Weibull modulus of the sintered samples are improved by 66%, 58%, and 45%, respectively. These improvements could be attributed to the higher amount of ???-Al2O3 phase, higher density and more uniform microstructure.