ANALYSIS OF AC-CONDUCTIVITY DATA OF BA1-XBIXF2+X SOLID-SOLUTIONS

Charge carriers concentrations N in the Ba1-xBixF2+x (0 less-than-or-equal-to x less-than-or-equal-to 0.45) solid solutions were estimated from an analysis of temperature and frequency dependences of the bulk ac-conductivities. They range from 3.10(21) to 1.10(22) (cm)-3 and are temperature independent. In addition, for the (x = 0.05) sample, the parameters of NNN-dipoles are estimated as follows : the reorientation frequency is nu(d) = 6.10(13) exp.(-0.60 ev./kT) s-1 and the NNN-dipoles concentration is N(d) = 9.10(19) (cm)-3. The comparison of the N values with the extended defect concentrations estimated on the basis of the clustering model which assumes in Ba1-x BixF2+x the progressive transformation with increasing x of 4:4:3:0 clusters into 8:12:1:0 cubooctahedral clusters, allows to propose that charge carriers governing the ionic conductivity properties are likely the interstitial fluoride ions belonging to the 4:4:3:0 clusters.