[en] Mechanism of fluorine ion diffusion was investigated with the ¹⁹F NMR method in monocrystal solid electrolytes Nd_1-xCa_xF_3-x (x=0; 0.01; 0.05; 0.10) having tysonite-type structure in the temperature range from 170 to 470 K. Ions of F(1) positions turn out to be the most active. Firstly formation of additional anionic vacancies in heterovalent substitutions of Ca²⁺ with Nd³⁺ improves dynamic characteristics of all fluorine ions (up to 5 mol%) and then with increase of substitutions degree the mobility of type F(1) ions drops. This fact explains the presence of maximum, noted in literature, on concentration dependence of electric conductivity. Exchange of fluorine ions between non-equivalent subsystems F(1) and F(2)-F(3) in diffusion with increase of substitutions degree grows which results in decrease of dynamic inhomogeneity in tysonite anionic sublattice