Conductivity parameters were deduced from an analysis of alternating-current data on fluorite-type solid solutions of the form: Sr1-xBixF2+x, where x was between 0 and 0.50. It was found that the compositional dependence of the fraction of charge carriers per unit cell agreed with estimates which were based upon a clustering model which assumed that interstitial fluoride ions of F' type were the long-range charge carriers in the present material.

E.F.Hairetdinov, N.F.Uvarov, M.Wahbi, J.M.Reau: Solid State Communications, 1997, 101[9], 681-6