Thermodynamic quantities and defect structure of La0.6St0.4Co1-yFeyO3-d (y=0-0.6) from high-temperature Coulometric titration experiments

M.H.R. Lankhorst, M.H.R. Lankhorst, Johan E. ten Elshof

Research output: Contribution to journalArticleAcademicpeer-review

90 Citations (Scopus)
46 Downloads (Pure)

Abstract

The partial energies and entropies of O2in perovskite-type oxides La0.6Sr0.4Co1−yFeyO3−δ(y=0, 0.1, 0.25, 0.4, 0.6) were determined as a function of nonstoichiometryδby coulometric titration of oxygen in the temperature range 650–950°C. An absolute reference value ofδwas obtained by thermogravimetry in air. The nonstoichiometry at a given oxygen pressure and temperature decreases with iron contenty. At low nonstoichiometries the oxygen chemical potential decreases withδ. The observed behavior can be interpreted by assuming random distribution of oxygen vacancies, an electronic structure with both localized donor states on Fe, and a partially filled itinerant electron band, of which the density of states at the Fermi level scales with the Co content. The energy of the Fe states is close to the energy at the Fermi level in the conduction band. The observed trends of the thermodynamic quantities can be interpreted in terms of the itinerant electron model only when the iron content is small. At high values ofδthe chemical potential of O2becomes constant, indicating partial decomposition of the perovskite phase. The maximum value ofδat which the compositions are single-phase increases with temperature.
Original languageUndefined
Pages (from-to)302-310
Number of pages9
JournalJournal of solid state chemistry
Volume130
Issue number130
DOIs
Publication statusPublished - 1997

Keywords

  • METIS-106471
  • IR-12054

Cite this