Review on the synthesis and doping strategies in enhancing the Na ion conductivity of Na3Zr2Si2PO12 (NASICON) based solid electrolytes

Na3Zr2Si2PO12 based solid electrolytes are well known materials because of their potential applications in different solid-state ionic devices. This review article presents the structural and transport results of Na3Zr2Si2PO12 based solid electrolytes prepared by different dry and wet methods known in the literature. The advantages and limitations of different synthesis methodologies to achieve the phase pure, high dense Na3Zr2Si2PO12 based materials are presented. The influence of the valence state, ionic radii of aliovalent dopants on the ionic conductivity of Na3Zr2Si2PO12 have been discussed with respect to their crystal structure. The role of sintering temperature, sintering durations, and sintering agents on the phase purity, density, and conductivity of Na3Zr2Si2PO12 based solid electrolytes are reviewed. Besides Na3Zr2Si2PO12 based polycrystalline solid electrolytes, the transport results of Na3Zr2Si2PO12 based grain boundary free glasses and flexible polymer electrolytes are also discussed. The applications of Na3Zr2Si2PO12 based solid electrolytes in different electrochemical devices are outlined.