Synthesis and characterization of novel 6-H perovskites Ba2Co2−xSbxO6−y, 0.6 ≤ x ≤ 0.8 and x = 1.33 (Ba3CoSb2O9)

6-H perovskites with compositions Ba2Co2−xSbxO6−y, 0.6≤x≤0.8 and x=1.33 (Ba3CoSb2O9) have been prepared in air at 1150 °C. Refinements of the crystal structures of Ba2Co1.4Sb0.6O6−y and Ba3CoSb2O9 were performed in space group P63/mmc, using neutron and X-ray powder diffraction data, respectively: Ba2Co1.4Sb0.6O6−y a=5.7315(1) Å, c=14.1118(4) Å, RF2=0.0669, Rp=0.0464, χ2=1.39; Ba3CoSb2O9 a=5.85321(7) Å, c=14.4454(2) Å, RF2=0.0458, Rp=0.0258, χ2=1.24. In Ba3CoSb2O9 the antimony atoms are located in pairs of face-sharing octahedra separated by cobalt atoms in octahedral layers, while in Ba2Co1.4Sb0.6O6−y a random distribution of B cations was found. In the latter structure, oxygen vacancies are preferably located in BaO3 planes separating the face-sharing octahedra. Electron diffraction and high-resolution electron microscopy studies showed that the structures are well ordered. Results of the magnetic susceptibility measurements of Ba3CoSb2O9 and Ba2Co1.4Sb0.6O6−y are reported.