Improved ionic conductivity of Na3+xScxZr2-xSi2PO12 (x=0.2, 0.3, 0.4, 0.5) NASICON via optimized sintering conditions: Investigation of crystal structure, local atomic structure, and microstructure

We report enhanced Na-ion conductivity of Na3+xScxZr2-xSi2PO12 (x = 0.2-0.5), prepared through solid-state reaction method with optimized sintering temperature of 1220 degrees C for 15 h. Among four compositions, Na3.4Sc0.4Zr1.6Si2PO12 offers highest total ionic conductivity of 2.6 mS/cm at 25 degrees C which is much higher than that of parent material. The Rietveld analysis of XRD data reveals a phase mixture of monoclinic and rhombohedral NASICON phases. NMR results indicate local disordering and a fast exchange of Na-ions between the different Na-sites. SEM observation reveals microcrack-free grain boundaries. An understanding of the underlying causes of higher conductivity has been achieved.

Automated summary

Enhanced Na-ion conductivity was achieved in Na3+xScxZr2-xSi2PO12 prepared through solid-state reaction with optimized sintering temperature, showing a significantly higher total ionic conductivity at 25 degrees C. The XRD analysis revealed a phase mixture of monoclinic and rhombohedral NASICON phases, while SEM observation showed microcrack-free grain boundaries.