ANALYSIS OF AC CONDUCTIVITY DATA OF THE ANION-EXCESS SR1-XTHXF2-SOLUTION WITH FLUORITE-TYPE STRUCTURE(2X SOLID)

Conductivity parameters, number of charge carriers, frequency of hoppi ng, have been determined from an analysis of ac conductivity data of t he Sr1-xThxF2+2x (0 less than or equal to x less than or equal to 0.22 5) solid solution with fluorite-type structure. The charge carrier con centration has been estimated: (ij from the frequency dependence of co nductivity, in accordance with the Almond-West approach; (ii) from the increment of the dielectric constant due to charge carriers. Similar results have been obtained by both approaches. The fraction of charge carriers per formula unit, evaluated as a function of composition, is in good agreement with the estimations made on the basis of the cluste ring process model which assumes that the charge carriers at long rang e in Sr1-xThxF2+2x are interstitial fluoride ions of F''' type. For x < 0.05, the results have been interpreted by the additional presence o f nn and nnn dipoles, the concentration and reorientation rate paramet ers of which have been evaluated.