Ternary oxides such as BaFe 12 O 19 (s), BaFe 2 O 4 (s), Ba 2 Fe 2 O 5 (s), Ba 3 Fe 2 O 6 (s) and Ba 5 Fe 2 O 8 (s) of Ba–Fe–O system were synthesized by solid-state reaction route taking stoichiometric proportions of preheated BaCO 3 (s) and Fe 2 O 3 (s) powders of high purities. The standard molar heat capacities of these ternary oxides were determined using differential scanning calorimetry from 310 to 850K. A heat capacity anomaly was observed for BaFe 12 O 19 (s), a member of magnetoplumbite group and largely used as hard ceramic magnet exhibited a heat capacity anomaly at 725K in differential scanning calorimetric result. This anomaly is due to the magnetic order–disorder transition from ferrimagnetic state to paramagnetic state of the compound and the transition temperature has been termed as Curie temperature (T C ). Thermodynamic functions such as ΔfHm° (298.15 K), Sm° (298.15 K), Sm°(T), Cp,m°(T), Hm°(T), {Hm°(T)−Hm° (298.15 K)}, Gm°(T), fef (free energy function), ΔfHm°(T) and ΔfGm°(T) for these ternary oxides were also calculated from 298 to 1000K using the second law analysis.