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.