Correlations between clusterization and electrical properties within fluorite-type anions excess solid solutions: Setting of a model

We proposed a model to correlate, in a continuous manner, the composition dependence of electrical properties and the progressive extension of clusterization when the substitution rate increases in a fluoride anion excess CaF₂-type solid solution of M_1–xM_x²⁺F_2+x(=1,2,3). A new classification of clusters is given based on the presence or absence of coexistence between two types of interstitial fluoride ions.The second part of the paper is devoted to the representation of the sum of interstitial fluoride ionsn_Fint and the sum of vacancies in normal sitesn according to the general equationy=(mx³+qx)/(x²+q). This model allows us to correlate the structural and electrical properties of a large number of solid solutions with fluorite-type structure.