NASICON (sodium superionic conductor) compounds have attracted considerable attention as promising solid electrolyte materials for advanced sodium (Na)-based batteries. In this study, we investigated the improvement in ionic conductivities of von-Alpen-type NASICON (vA-NASICON) ceramic electrolyte by introducing magnesium (Mg2+) as a heterogeneous element. The optimal Mg-doped vA-NASICON exhibited a high ionic conductivity of 3.64 × 10−3 S cm−1, that was almost 80% higher than that of un-doped vA-NASICON. The changes in the physicochemical properties of vA-NASICONs through Mg introduction were systematically analyzed, and their effects on the ionic conductivities of vA-NASICON were studied in detail. When the optimal ratio of Mg2+ was used in the synthetic process, the relative density (96.6%) and grain boundary ion conductivity were maximized, which improved the total ionic conductivity of vA-NASICON. However, when Mg2+ was introduced in excess, the ionic conductivity decreased because of the formation of an undesired NaxMgyPO4 secondary phase. The results of this study are expected to be effectively applied in the development of advanced sodium-based solid electrolytes with high ionic conductivities.
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