Structure, oxygen non-stoichiometry and thermal properties of (Bi0.4Sr0.6)Sr2CoO5–δ

• Cobaltite (Bi0.4Sr0.6)Sr2CoO5−δ was prepared and its structure was refined.
• Oxygen non-stoichiometry of (Bi0.4Sr0.6)Sr2CoO5−δ was determined by TG.
• Thermodynamic properties were measured by PPMS, DSC and drop calorimetry.
• The heat capacity was analyzed using Debye–Einstein model and considering a variable oxygen stoichiometry.

We synthesized and characterized (Bi0.4Sr0.6)Sr2CoO5−δ using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS). In the next step the heat capacity and enthalpy increments of (Bi0.4Sr0.6)Sr2CoO5−δ were measured by physical property measurement system (PPMS), differential scanning calorimetry (DSC) and drop calorimetry. Oxygen non-stoichiometry was determined using thermogravimetric measurement (TG) and reduction in hydrogen atmosphere. Above room temperature the temperature dependence of the molar heat capacity in the form Cpm = (201.0 + 0.09261 × T − 2184097 × T−2) J K−1 mol−1 was derived by the least squares method from the experimental data. The heat capacity was also analyzed in terms of a combined Debye–Einstein model. The molar entropy Sm° (298.15) = 219.65 J mol−1 K−1 was evaluated from the low temperature heat capacity data.