The Structure, Nonstoichiometry,
and Thermodynamic Characteristics of Oxygen
in Strontium Ferrite Doped with Niobium, SrFe_{1 x}Nb_xO₃

P. V. Anikina, A. A. Markov, M. V. Patrakeev, I. A. Leonidov, and V. L. Kozhevnikov

Institute of Solid-State Chemistry, Ural Division, Russian Academy of Sciences,
ul. Pervomaiskaya 91, Yekaterinburg, 620041 Russia

e-mail: anikina@ihim.uran.ru

Received February 28, 2008

Abstract—The influence of doping with niobium on the structure and oxygen nonstoichiometry of strontium
ferrite SrFe_1xNb_xO₃ (x = 0.05, 0.1, 0.2, 0.3, and 0.4) was studied. The content of oxygen in the doped deriv-
atives was determined by coulometric titration as a function of temperature (650950C) and oxygen partial
pressure in the gas phase (10⁴–1 atm). The partial molar enthalpies (x, ) and entropies (x, ) of oxy-
gen in SrFr_1xNb_xO₃ were calculated. An analysis of (x, ) dependences showed that the model of a ran-
dom distribution of ions and vacancies over accessible sites in the oxygen sublattice allowed the experimental data
to be described satisfactorily. An increase in the partial enthalpy (x, ) as nonstoichiometry decreased was
indicative of weak repulsive interactions between oxygen ions in the structure of SrFe_1xNb_xO₃.

DOI: 10.1134/S0036024409050021

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