Determination of Gibbs energies of formation of CaFe2O4 and Ca2Fe2O5 from solid-state EMF measurements using CaF2 as solid electrolyte
2002 (English)In: Metallurgical and Materials Transactions B-Process Metallurgy and Materials Processing Science, ISSN 1073-5615, Vol. 33, no 3, 385-92 p.Article in journal (Refereed) Published
The standard Gibbs energy change for the reactions CaO + Fe2O3 --> CaFe2O4 and 2 CaO + Fe2O3 --> Ca2Fe2O5 has been determined from solid-state electromotive force (emf) measurements, using CaF2 as solid electrolyte. The temperature dependence of the standard Gibbs energies of formation from the elements is represented by the equations
Delta(f)G(o)(CaFe2O4) = - 1448.4 x 10(3) + 128.0 T + 27.95 T In (T) (+/- 1800) J mol(-1)
1030 < T/K < 1280
Delta(f)G(o)(Ca2Fe2O5) = -2049.9 x 10(3) - 12.84 T + 55.91 T In (T) (+/-2800) J mol(-1)
1140 < T/K < 1340
By applying a "third-law" analysis of the experimental data, the standard enthalpy of formation of CaFe2O4 from constituent oxides at 298 K was evaluated as DeltaH(298)(o)(CaFe2O4) = - 17.5 +/- 0.4 kJ mol(-1). A description of the developed apparatus for emf measurements is given.
Place, publisher, year, edition, pages
2002. Vol. 33, no 3, 385-92 p.
THERMODYNAMIC PROPERTIES; HEAT-CAPACITY; STABILITY; CAO
IdentifiersURN: urn:nbn:se:umu:diva-9061OAI: oai:DiVA.org:umu-9061DiVA: diva2:148732