Upper Limit of the Mobility and Concentration of Charge Carriers in Fluoride Superionic Conductors with Fluorite and Tysonite Structures

The maximum values of the mobility and concentration of charge carriers in fluoride superionic conductors of the fluorite (CaF₂, SrF₂, BaF₂, and PbF₂) and tysonite (LaF₃) structural types have been calculated within the crystallophysical model. It is shown that the upper limits of the ionic conductivity and carrier mobility and concentration in the crystalline state of fluoride superionics are, respectively, 4 ± 1 S/cm, (5 ± 1) × 10⁻³ cm²/(V s), and (5 ± 2) × 10²¹ cm⁻³ (10 ± 4% of the total amount of fluorine ions).