Synthesis of magnesium-beta-alumina composite electrolytes via a vapour phase method

Abstract

γ-Al2O3, Na2CO3, MgCO3 and Li2CO3 were employed to synthesise MgO-doped Na-β″-Al2O3 composite electrolytes via a vapour phase method. The effects of MgO content on the β″-Al2O3 content, microstructure and electrical properties of each of the composite electrolytes were investigated by using X-ray diffraction, scanning electron microscopy and AC impedance spectroscopy, respectively. The bulk density and bending strength of the samples were also measured in this study. The results demonstrate that the composite electrolyte with an appropriate amount of MgO increased the β″-Al2O3 content of the solid electrolytes and accelerated their densification. The spinel phase resulting from MgO doping not only assisted the conversion process, but also facilitated the formation of Na1.67Mg0.67Al10.33O17. Lastly, the Na-β″-Al2O3 composite electrolyte doped with 0.4 wt% MgO was found to exhibit the best ionic conductivity and bending strength among all of the electrolytes.