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Characterization of the mixed perovskite BaSn1–xSbxO3 by electrolyte electroreflectance, diffuse reflectance, and X-ray photoelectron spectroscopy

1989; Royal Society of Chemistry; Volume: 85; Issue: 4 Linguagem: Inglês

10.1039/f19898500907

2050-5655

Gerardo Larramona, Claudio Gutiérrez, M.I. da Silva Pereira, Manuel Rosa Nunes, Fernanda Costa,

Advancements in Solid Oxide Fuel Cells

The band gap of the mixed perovskite BaSn1–xSbxO3 has been reported to be 134 kJ mol–1(J-M. Hermann, M. R. Nunes and F. M. A. da Costa, J. Chem. Soc., Faraday Trans. I, 1982, 78, 1983), corresponding to 1.4 eV, which is the optimum value for solar-energy conversion. In order to confirm this value, pressed discs of the mixed perovskite were sintered at 1673 K and made into electrodes, and their electrolyte electroreflectance (e.e.r.) spectra measured. The band gap was determined by fitting the e.e.r. spectra to Aspnes' formula for the low-field regime. The band gap of the pure, insulating perovskite BaSnO3 was determined from its diffuse reflectance spectrum, after application of the Kubelka–Munk formula. The band gap of the mixed perovskite was constant and equal to 330 kJ mol–1 for Sb concentrations in the range x= 0–10%, in agreement with the observed constancy of the lattice parameter for x= 0–17%, the range over which the perovskite exists as a single phase. The high band-gap energy of this material makes it unsuitable for solar-energy conversion. X-Ray photoelectron spectroscopy measurements showed that all the Sb in the mixed perovskite was present as SbV, as would be expected from the high conductivity of the samples. From the atomic ratios it was concluded that probably the surface of the pure BaSnO3 perovskite is enriched in SnO2, and that of the mixed perovskite in Sb2O5.