Heat capacity, enthalpy and entropy of Sr14Co11O33 and Sr6Co5O15

Heat capacity and enthalpy increments of two ternary strontium cobalt mixed oxides Sr14Co11O33 and Sr6Co5O15 were measured by the relaxation time method (2–250 K), DSC (258–355 K) and drop calorimetry (573–1173 K). Temperature dependencies of the molar heat capacity in the form Cpm = 1359.46 + 0.355826·T–19.5816·106·T−2 J K−1mol−1 for Sr14Co11O33 and Cpm = 515.81+ 0.313326·T–5.07872·106·T−2 J K−1mol−1 for Sr6Co5O15 respectively, were derived by the least-squares method from the experimental data. The heat capacity was analyzed in terms of a combined Debye–Einstein model. The molar entropies at 298.15 K, Sm(298.15 K) = 1339.76 J K−1mol−1 for Sr14Co11O33 and Sm(298.15 K) = 578.77 J K−1mol−1 for Sr6Co5O15 were evaluated from the low temperature heat capacity measurements.