Conditions for synthesizing single-phase solid solutions Bi 4V2 - x Cu x/2Ti x/2O 11 - x and Bi4 - x/2V2 - x/2Cu x/2Ti x/2O11 - x/2 are studied. The sequence of phase transformations is determined. Possible domains of stability of polymorphic modifications and the overall conductivity as a function of temperature and composition are studied. The structure of the γ-modification is refined using Rietveld's full-profile analysis.