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

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 Na_1.67Mg_0.67Al_10.33O₁₇. 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.