The dynamics of crystal lattices of potassium, rubidium, and cesium heptafluorodiantimonates(iii) and specific features of internal rotations of the Sb2F7 fluoride groups in these compounds were studied using 123Sb NQR in the temperature interval from 77 to 325 K and 19F NMR in the temperature interval from 240 to 470 K in combination with X-ray diffraction and thermogravimetric analyses. The distinctions in the dynamic behavior of the fluoride ions with changing the size (polarizability) of outer-sphere cations are discussed. The structural phase transition in CsSb2F7 was revealed at 425—430 K accompanied by the appearance of a high ion conductivity (σ ≈ 1.3·10–3 S cm–1 at 450 K). A second type phase change can exist at 220—270 K.