Phase diagram of the pseudobinary system Bi–Co–O

Samples with different ratios of Bi₂O₃ and Co₂O₃ were prepared by ceramic route. Based on the results of differential thermal analysis, X-ray powder diffraction, SEM–EDXA and FactSage database the phase diagram of the Bi–Co–O diagram in air atmosphere was assessed and calculated using the FactSage software. The sillenite structure of Bi₂₄Co₂O₃₉ was identified and the single phase homogeneity range of Bi₂₄Bi_2?xCo_xO₃₉, x = 0.9–2.0 was determined by Rietveld analysis and SEM–EDXA. To verify the composition in the various parts of the phase diagram at elevated temperatures, a number of high-temperature annealing experiments was performed followed by rapid quenching to room temperature.