Synthesis of Na-β″-Al2O3 electrolytes by microwave sintering precursors derived from the sol–gel method

Na-β″-Al2O3 electrolytes were synthesized by the microwave sintering assisted sol–gel technique in this study. The precursor powders and microwave-sintered pellets were systematically investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), differential scanning calorimetry (TG–DSC) and Fourier transform infrared (FT-IR) spectroscopy. The ionic conductivity of the microwave-sintered pellets was also measured based on AC impedance spectroscopy. It was found that the calcining temperature of the precursor powders derived from the sol–gel method was the key factor to affect the purity of Na-β″-Al2O3 in the pellets. The sintered pellets prepared from the powders calcined at 850 °C exhibited a purity of 94.4% Na-β″-Al2O3 and the density of the sintered pellets was 98.91% of the theoretical density of Na-β″-Al2O3. In addition, the sample showed an ionic conductivity of 0.01085 S cm−1 at 300 °C by AC impedance measurement.