Anomalously High Fluorine Mobility in Tysonite-Like LaF 3 :ScF 3 Nanocrystals: NMR Diffusion Data
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Applied Magnetic Resonance
ORIGINAL PAPER
Anomalously High Fluorine Mobility in Tysonite‑Like LaF3:ScF3 Nanocrystals: NMR Diffusion Data L. B. Gulina1 · A. F. Privalov2 · M. Weigler2 · I. V. Murin1 · V. Tolstoy1 · M. Vogel2 Received: 28 May 2020 / Revised: 29 July 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract Nanosized La0.93Sc0.07F3 superionic conductor with tysonite structure was obtained at the gas–solution interface after interaction of aqueous salt solution with gaseous HF. NMR diffusion studies show that homovalent substitution of L a3+ by S c3+ with a smaller ionic radius leads to around four orders of magnitude faster fluorine diffusion as compared with crystalline L aF3 and faster as in all previously studied nanosized LaF3 and heterovalent-doped nanosized L a0.95Sr0.05F2.95. The homovalent doping is a new route to improve the conductivity of tysonite-structured nanomaterials.
1 Introduction Solid electrolytes based on inorganic fluorides become widely used in chemical sensors, voltaic cells, and many other solid-state electrochemical devices [1]. At medium temperatures, the most promising fluorine superionic conductors are the MII F solid solutions with crystal structures of tysonite or fluorite RIII 1−x x 3−x where III II R —is the Y, Sc, or another rare-earth element, and M —is the alkaline-earth element or Pb. LaF3, crystallizing in tysonite structure, is a prospective ion-conducting solid electrolyte due to its inert nature and high F-conductivity. A number of works [2–8] investigated the influence of crystallochemical features of the tysonite matrix on the ionic transport. Non-stoichiometric heterovalent La1−xMxF3−x solid solutions (M–Ca, Sr, Ba, Pb; 0
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