Synthesis of lithium-doped Na-β"-alumina composite electrolytes by a vapor phase process

In this work, Na-beta ''-alumina composite electrolyte was prepared with nano-eta-alumina powder by a vapor phase process in which Na2CO3, Li2CO3 and MgO were used as additives. The thermoanalysis, formation of beta ''/beta phase, microstructure and ionic conductivity were studied by thermogravimetry/differential scanning calorimetry (TG/ DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS), respectively. The results demonstrated that nano-eta-alumina has a small size and high activity, and the relative density of the sample sintered at 1400 degrees C by hot-pressed sintering is 99.2%. The spinet phase formed by MgO doping in the sintering process of alumina can accelerate the process of vapor phase. The addition of Li2O dopant significantly improved the properties of Na-beta ''-alumina composite electrolyte by increasing the content of beta ''-alumina phase and promoting the formation of layers microstructure. The total conductivity showed a linear dependence on the temperature (200-500 degrees C), which fitted well with the Arrhenius equation. Na-beta ''-alumina composite electrolyte doped with 0.6 wt% Li2O showed the preferable ionic conductivity.