Arrhenius Behavior of the Bulk Na-Ion Conductivity in Na3Sc2(PO4)3 Single Crystals Observed by Microcontact Impedance Spectroscopy

Daniel Rettenwander, Günther J. Redhammer, Marie Guin, Artur Benisek, Hannes Krüger, Olivier Guillon, Martin Wilkening, Frank Tietz, Jürgen Fleig

Research output: Contribution to journalArticleResearchpeer-review

Abstract

NASICON-based solid electrolytes with exceptionally high Na-ion conductivities are considered to enable future all solid-state Na-ion battery technologies. Despite 40 years of research the interrelation between crystal structure and Na-ion conduction is still controversially discussed and far from being fully understood. In this study, microcontact impedance spectroscopy combined with single crystal X-ray diffraction, and differential scanning calorimetry is applied to tackle the question how bulk Na-ion conductivity σbulk of sub-mm-sized flux grown Na3Sc2(PO4)3 (NSP) single crystals is influenced by supposed phase changes (α, β, and γ phase) discussed in literature. Although we found a smooth structural change at around 140 °C, which we assign to the β → γ phase transition, our conductivity data follow a single Arrhenius law from room temperature (RT) up to 220 °C. Obviously, the structural change, being mainly related to decreasing Na-ion ordering with increasing temperature, does not cause any jumps in Na-ion conductivity or any discontinuities in activation energies Ea. Bulk ion dynamics in NSP have so far rarely been documented; here, under ambient conditions, σbulk turned out to be as high as 3 × 10-4 S cm-1 at RT (Ea, bulk = 0.39 eV) when directly measured with microcontacts for individual small single crystals.

Original languageEnglish
Pages (from-to)1776-1781
Number of pages6
JournalChemistry of Materials
Volume30
Issue number5
DOIs
Publication statusPublished - 13 Mar 2018

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry

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  • NAWI Graz

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