Ceramics-Silikáty 57 (2) 83-86 (2013)

THERMAL PROPERTIES AND HOMOGENITY RANGE OF Bi_24+xCo_2-xO₃₉ CERAMICS

Jankovsky O., Sedmidubsky D., Sofer Z., Capek J., Ruzicka K.

Samples with different Bi₂O₃/Co₂O₃ ratio were prepared by ceramic route. Based on the results of DTA, XRD and SEM – EDX a section of phase diagram of the Bi–Co–O diagram in air atmosphere was calculated using the FactSage software. The sillenite structure of Bi_24+xCo_2-xO₃₉ was confirmed and described. The Rietveld analysis confirmed SEM – EDX results. The heat capacity and enthalpy increments of Bi₂₄Co₂O₃₉ were measured by differential scanning calorimetry (DSC) from 258 K to 355 K and by the drop calorimetry from 573 K to 973 K. Above room temperature the temperature dependence of the molar heat capacity in the form C_pm = (1467.87 + 0.299410 · T – 15888378 · T^-2) J K^-1 mol^-1 was derived by least-squares method from the experimental data.

Keywords: Cobalt sillenite, Thermal properties, Heat capacity