LAUSR

Abstract Ionic conductors based on PbF2, being one of the archetypes to study ion dynamics, serve as excellent model substances to study the elementary steps of translational anion dynamics in the solid state. Here, high-energy ball milling was employed to prepare a structurally disordered, metastable solid solution by mixing PbF2 with CaF2. The cation-mixed lattice in cubic Ca0.4Pb0.6F2 provides a range of magnetically distinct fluorine sites. We used 2D 19F magic angle spinning nuclear magnetic resonance (NMR) exchange spectroscopy to reveal the site preference of the F anions when hopping through the lattice. It turned out that the F anions located in sites coordinated by Pb cations are more mobile than those residing near or in Ca-rich environments. Conductivity measurements and variable-temperature 19F NMR spin-lattice relaxation experiments provide activation energies (0.24 eV, 0.40 eV) from which we deduce that in cation-mixed Ca0.4Pb0.6F2 anion diffusivity, on the angstrom length-scale, is mainly determined by vacant F− sites. Macroscopic ion transport has to be characterized by an activation energy of 0.55 eV suggesting that the F anions also use interstitial sites for long-range ionic transport.