Ion mobility and conductivity in fluorite-type solid solutions in the KF–MF2–BiF3 systems (M = Ba, Cd) according to 19F NMR and conductivity data

• Studied the ion mobility, conductivity in K0.5 − xMxBi0.5F2 + x solid solutions (M = Ba,Cd).
• An analysis of 19F NMR spectra made it possible to identify types of ion mobility.
• The main type of ion motion above 350 K in solid solutions is a diffusion of ions F−.
• The ionic conductivity of the solid solutions studied more than 10− 2 S/cm above 460 K.

Ion mobility and transport properties of the fluorite-type K0.41Ba0.09Bi0.5F2.09, K0.41Cd0.09Bi0.5F2.09, K0.45Ba0.05Bi0.5F2.05, and K0.45Cd0.05Bi0.5F2.05 solid solutions were studied by the 19F NMR spectroscopy and conductivity measurements. Analysis of 19F NMR spectra made it possible to assess the temperature effect on the nature of ion motions in the fluoride sublattice, identify types of ion mobility, and determine the respective temperature ranges (150–470 K). The results showed that the dominant type of ion motion is diffusion of fluoride ions in these solid solutions at temperatures above 350 K. The samples have the ionic conductivity above 10−2 S/cm at 463 K.