Standard enthalpy of formation and heat capacity of compounds in the pseudo-binary Bi2O3–Fe2O3 system

Bismuth ferrites, Bi2Fe4O9, BiFeO3, and Bi25FeO39 have been prepared and characterized. The thermodynamic data such as standard molar enthalpies of formation ΔfHm°(298.15K) and standard molar heat capacity (Cp°) were obtained from the solution calorimetry and calvet calorimetric measurements. ΔfHm°(298.15K) for Bi2Fe4O9(s), BiFeO3(s), and Bi25FeO39(s) were found to be (−2476.0 ± 4.3), (−768.4 ± 2.9) and (−7699.8 ± 17.3) kJ mol−1, respectively. The dependence of molar heat capacity Cp°Cp° with temperature can be given asCp°(Bi2Fe4O9,s)(JK-1mol-1)=353.81+0.01774T-1.63606×105/T2(313