Oxygen non-stoichiometry and thermodynamic properties of Bi2Sr2CoO6+ ceramics

Abstract

In the literature the structure Bi 2 Sr 2 CoO 6+ δ has been described with a variable oxygen nonstoichiometry δ . We identified δ parameter by thermogravimetric measurements and determined thermodynamic properties of Bi 2 Sr 2 CoO 6+ δ . The heat capacity and enthalpy increments of Bi 2 Sr 2 CoO 6+ δ were measured by the relaxation time method (PPMS) from 2 to 256 K, by differential scanning calorimetry (DSC) from 258 to 355 K and by drop calorimetry from 573 to 1123 K. Above-room temperature, the dependence of molar heat capacity under isodynamical (constant p O 2 ) and conventional isoplethal conditions (constant composition) was derived from the experimental data by the least-squares method. The low temperature heat capacity was analyzed in terms of a combined Debye–Einstein model. The molar entropy S m ∘ ( 298.15 ) = 318.9 J K − 1 mol − 1 was evaluated from the low-temperature heat-capacity measurements.