Vol.:(0123456789) Applied Magnetic Resonance https://doi.org/10.1007/s00723-020-01247-5 1 3 ORIGINAL PAPER Anomalously High Fluorine Mobility in Tysonite‑Like LaF 3 :ScF 3 Nanocrystals: NMR Difusion Data L. B. Gulina 1  · A. F. Privalov 2  · M. Weigler 2  · I. V. Murin 1  · V. Tolstoy 1  · M. Vogel 2 Received: 28 May 2020 / Revised: 29 July 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020 Abstract Nanosized La 0.93 Sc 0.07 F 3 superionic conductor with tysonite structure was obtained at the gas–solution interface after interaction of aqueous salt solution with gaseous HF. NMR difusion studies show that homovalent substitution of La 3+ by Sc 3+ with a smaller ionic radius leads to around four orders of magnitude faster fuorine difu- sion as compared with crystalline LaF 3 and faster as in all previously studied nano- sized LaF 3 and heterovalent-doped nanosized La 0.95 Sr 0.05 F 2.95 . The homovalent dop- ing is a new route to improve the conductivity of tysonite-structured nanomaterials. 1 Introduction Solid electrolytes based on inorganic fuorides become widely used in chemical sensors, voltaic cells, and many other solid-state electrochemical devices [1]. At medium temperatures, the most promising fuorine superionic conductors are the solid solutions with crystal structures of tysonite or fuorite R III 1-x M II x F 3-x where R III —is the Y, Sc, or another rare-earth element, and M II —is the alkaline-earth ele- ment or Pb. LaF 3 , 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 infuence of crystallochemical features of the tysonite matrix on the ionic transport. Non-stoichiometric heterovalent La 1−x M x F 3−x solid solutions (M–Ca, Sr, Ba, Pb; 0 <x ≤ 0.2) with tysonite structure often exhibit signifcantly enhanced ionic conductivities and difusion coefcients compared to pure LaF 3 . This occurs because of local charge compensation in the cationic sublattice when replac- ing La 3+ by M +2 alkaline earth metal or lead ions [9–12]. Advanced nanochemistry Applied Magnetic Resonance * A. F. Privalov alexei.privalov@physik.tu-darmstadt.de 1 Institute of Chemistry, Saint Petersburg State University, Universitetskaya nab. 7/9, St. Petersburg 199034, Russia 2 Institut für Festkörperphysik, TU Darmstadt, Hochschulstr. 6, 64289 Darmstadt, Germany