In this paper we present a detailed study of structural and dynamical properties of theCdF2–PbF2 systems. Particular attention is devoted to the processes involving the phase separation, aphenomenon of fundamental importance in the correct description of some dynamicalproperties, as introduced in our previous works. We show here, that the phaseseparation trend is observed in the undercooled melt, whether by cooling the liquidbelow its melting point, or by heating a homogeneous glass at temperatures aboveTg. The degree of phase separation depends on the procedure employed to obtain thecrystalline materials, and the simplest way to determine this property is by performing anisothermal treatment in the undercooled melt region. The local fluorine environmentsQ(n), corresponding tofluorine surrounded by nPb and 4-nCd neighbors, is used as a probe in the average local composition. We demonstratethat the increase in the structural inhomogeneity around the composition withx = 0.35 is the factor which leads to a better fluorine conducting property for theCd0.35Pb0.65F2 solid solution, in addition to providing a correct determination of the melting temperature of theCdxPb1−xF2 compositions.