Ion mobility and conductivity in the K0.45Bi0.55–xInxF2.1 solid solutions with fluorite structure according to 19F NMR and conductivity data

Abstract

Ion mobility and conductivity of K0.45Bi0.55–xInxF2.1 (x = 0, 0.05, 0.1, 0.15) solid solutions with fluorite structure have been investigated using the methods of 19F NMR, X-ray diffraction and impedance spectroscopy. Several types of fluoride ions in the solid solution composition were established by analyzing the 19F NMR spectra at 150 K and the belonging of fluoride ions to a specific sublattice was established by deconvolution of the spectra registered. Types of ionic motions in the fluoride sublattice of solid solutions have been considered and temperature ranges of their realization have been determined (150–450 K). Diffusion of the fluoride ions above 300–350 K is a dominating type of ionic motions in the fluoride sublattice of solid solutions under study. Due to high ionic conductivity, 1.8 × 10−2–6.3 × 10−4 S/cm at 550 K (Ea = 0.38–0.46 eV), these solid solutions can be considered as superionic conductors.