[en] A continuous series of Bi₄Ba_xV_2-xO_11-(3x/2)-δ solid solutions are prepared by conventional solid state reactions. The polymorphism and electrical properties of these samples are studied by FT-IR spectroscopy, X-ray diffraction, differential thermal analysis (DTA) and AC impedance. The solid solutions with composition 0.07≤x≤0.13 are isostructural with the monoclinic phase α-Bi₄V₂O₁₁. However, orthorhombic β-phase is observed for x=0.17 and tetragonal γ-phase is stabilized for x≤0.30. X-ray and DTA results reveal the occurrence of α↔γ transition for x≤0.13, β↔γ transition for x=0.17 and γ'→γ transition for x≥0.20. AC impedance plots at 280 deg. C for all compositions show greater contribution of grain to ionic conductivity than grain boundary. The highest ionic conductivity, σ_300^oC=4.456x10^-5 S cm^-1 is observed for x=0.17. The ionic conductivity of the substituted compounds is higher than the parent α-Bi₄V₂O₁₁, due to the increased oxygen ion vacancies generated as a result of barium doping.