Effect of Na2O content on properties of beta alumina solid electrolytes

Beta alumina ceramics are well-known fast-ionic conductors of Na-ion. The effect of Na2O content (8.00–13.19%) on properties of beta alumina solid electrolytes was studied in the paper by XRD, SEM and EIS. The results showed that in the Na2O–Al2O3 system, the β″-Al2O3 phase was formatted at the low temperature of 1250 °C, however the noticeable transformation from β″-Al2O3 to β-Al2O3 occurred in the higher temperature range. The β″-phase content of the precursor powders was independent of the Na2O content, but β″-phase content, the volume density and the bending strength of beta alumina sinters grew with the increase of the Na2O content. Samples with 10.84% Na2O possessed the optimum ionic conductivity and the most uniform microstructure. The ionic conductivity depends not only on the phase content, but also on the phase microstructure.