Ordered Tysonite-like Phases

Figure 14.16 Solid solution in the BiF3-Bi203-BaF2 system at 873 K [34],R Ba4Bi3pi7 based phase, (3 (3-BiOyF3 2y based phase 0 fluorite-like BaF2 based solid solution, I, II tysonite-like solid solutions. III ordered tysonite-like phase BiOyFs 2y(0.13

Functionalized Inorganic Fluorides 14.7J2 Ordered Tysonite-like Phases... 

A maximum on concentration dependences of the conductivity at x 0,07 was observed for the tysonite-like Bij xBax(0,F)3 solid solution with the structure I (Rgure 14.39). The discoveiy of the ordered tysonite-like BiOyF3 2y phase (0.13 clustering mechanism described... 

However at high concentrations of anion vacancies (and correspondingly, O p or M bj defects), at almost invariable unit ceU parameters, defect ordering occurs with formation of defect clusters and new phases. Micro-ordering and crystallization processes of the tysonite-like ordered phases reduce anionic conductivity of materials. 

The following clustering and probably local cluster ordering (similar to fluorites, see Section 14.5.2) in the structure leads to a decrease of the charge carrier concentration and to a blocking of a part of the conductivity channels. It negatively affects the transport properties of these phases. AU these factors lead to the appearance of a maximum on the curve of conductivity, a=f(x) atx = 0.05 (Figure 14.38). Similar extremes were observed on concentration dependences of transfer characteristics of tysonite-like MxRi xF3 2x (M = Ca, Sr, R = La-Lu) solid solutions [115]. 

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