Pronounced diffuse phase transitions of Schottky type are found by cp measurement for fluorites PbF2, SrCl2 and BaF2 at higher temperatures. Formation energies and entropies are calculated for isolated defects from the transition curves. From the energy and entropy of transition an upper and a lower limit can be derived for higher defect concentrations. It is seen that these concentrations scarcely exceed 10 % immediately below the melting point. BaCl2 is distinguished among the other fluorites showing an absolutely sharp transition instead of a diffuse one at 1 195 K