Bi2Ca2O5, Bi2CaO4 and Bi24Co2O39 double oxides are of interest as intermediate phases at preparation of Bi2Ca2Co1,7Oy and (Ca,Bi)3Co4O9+d oxide thermoelectrics and as admixtures to the heterogeneous ceramics based on these layered oxides. In this work Bi2Ca2O5, Bi2CaO4, and Bi24Co2O39 ceramic samples were prepared using solid-state reactions method from Bi2O3, CaCO3, and Co3O4 in air within the temperature range of 923–1143 K. The crystal structure of the samples was studied by X-ray diffraction (XRD) analysis using Bruker D8 XRD Advance with monochromatic CuKa radiation (l = 1.5406 Å). Thermal expansion, electrical conductivity (s), dielectric permittivity (e) and dielectric losses (tgd) of ceramics were studied in air in the temperature range of 290–1070 K. Bi2Ca2O5 crystallizes in the triclinic system (a = 1.01(2) nm, b = 1.01(5) nm, c = 1.05 nm, a = 116.9(1)°, b = 107.14(3)°, g = 92.89°, V = 0.890 nm3, ρXRD = 6.47 g/cm3), Bi2CaO4 - in the monoclinic one (a = 1.664(7) nm, b = 1.162(1) nm, c = 1.402(7) nm, b = 134.17(2)°, V = 1.945(26) nm3, ρXRD = 7.13 g/cm3), and Bi24Co2O39 - in the cubic one (a = 1.021(1) nm, V = 1.063(16) nm3, ρXRD = 9.00 g/cm3). Apparent density values of the sintered ceramics are 5.78, 4.82, and 7.42 g/cm3 for Bi2Ca2O5, Bi2CaO4, and Bi24Co2O39 compounds, respectively. It was found that electrical conductivity of the materials studied had semiconducting character, and increasing in the bismuth oxide content in ceramics leads to the increasing its electrical conductivity, dielectric permittivity, and dielectric losses values. The values of average linear thermal expansion coeffient are equal to 12.9×10–6, 14.7×10–6, and 16.0×10–6 K–1. Activation energy of electrical conductivity are equal to 1.393, 1.159, and 0.499 eV, and temperature of maximum of dielectric losses due to dipole polarization are equal to 923, 780, and 681 К for the Bi2Ca2O5, Bi2CaO4, and Bi24Co2O39 ceramics, respectively. On the temperature dependence of dielectric permittivity of Bi24Co2O39 phase the local maximum at 845 K was detected, which is connnected, obviously, to the partial disordering of dipoles in its crystal structure.Forcitation:Klyndyuk A.I., Krasutskaya N.S. Thermal expansion and electrical properties of Bi2Ca2O5, Bi2CaO4 and Bi24Co2O39 double oxides. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 10. P. 30-35