Influence of Nb5+, Ti4+, Y3+ and Zn2+ doped Na3Zr2Si2PO12 solid electrolyte on its conductivity

In this study, Na3Zr2-xNb0.8xSi2PO12, Na3Zr2-xTixSi2PO12, Na3Zr2-xYxSi2PO12-0.5x, Na3Zr2-xZnxSi2PO12-x ceramics with x = 0.1, 0.2, 0.3 and 0.4 were sintered to explore the influence of the valence state and the content of dopants on the conductivity of NASICON solid electrolyte. Archimedes method, X-ray diffraction, scanning electron microcopy and complex impedance spectroscopy were used to characterize the sintered samples. Results show that the dopant with +2 oxidation state cations improves the bulk conductivity mainly due to the less electrostatic interactions between Zn2+ ions and Na+ ions. The optimal doping content of Nb5+, Ti4+ and Y3+ doped NASICON ceramics is 0.1 mol and that of Zn2+ doped NASICON ceramic is 0.2 mol for the highest ionic conductivity. Among all the doped NASICON ceramics, Na3Zr1.8Zn0.2Si2PO11.8 ceramic displays the highest total conductivity of 1.44 × 10−3 S/cm and bulk conductivity of 3.41 × 10−3 S/cm at room temperature. Furthermore, doping strategy both increases the density and decreases the sintering temperature of Na3Zr2Si2PO12 ceramic.