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

• Published in: Chemical physics letters Vol. 776
• Main Authors: Santhoshkumar, B., L.R. Khanna, D., Choudhary, M.B., Lokeswara Rao, P., Ramanathan, K.V., Bera, A.K., Yusuf, S.M., Pahari, Bholanath
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-08-2021
• Subjects: Ionic conductivity; MAS NMR; NASICON; SEM; Sodium batteries; SEM; NASICON; MAS NMR; Ionic conductivity; Sodium batteries
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2021.138706

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•Sc3+ doped Na3Zr2Si2PO12 NASICONs were prepared using solid state reaction method with optimized sintering conditions.•They show much higher Na-ion conductivity (>2.0 mS/cm at 25 °C and > 20 mS/cm at 100 °C) than that of pure Na3Zr2Si2PO12.•The local structure, the crystal structure, and the microstructure of the NASICONs have been determined.•The role of structure on grain and grain boundary conductivity has been investigated.•The Sc3+ doped Na3Zr2Si2PO12 offers a greater prospect in Na-ion battery applications.
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 °C for 15 h. Among four compositions, Na3.4Sc0.4Zr1.6Si2PO12 offers highest total ionic conductivity of 2.6 mS/cm at 25 °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.