(Ln_1.8Fe_0.2)FeSbO₇ (Ln = Pr–Tb) Mixed Oxides with the Pyrochlore Structure in CO Oxidation Reaction

Abstract

: (Ln_1.8Fe_0.2)FeSbO₇ (Ln = Pr–Tb) mixed oxides have been synthesized via coprecipitation followed by annealing. According to Rietveld refinement results, all of the oxides have the pyrochlore structure (sp. gr. Fd$\overline{3}$mz). The (Ln_1.8Fe_0.2)FeSbO₇ compounds have been shown to exhibit high activity for CO oxidation reaction. The best results have been obtained for (Pr_1.8Fe_0.2)FeSbO₇, which has a 90% CO conversion temperature T₉₀ = 385°C. With increasing lanthanide atomic number, T₉₀ rises monotonically from 385 to 550°C in going from Pr to Tb. This behavior is most likely due to the decrease of structural imperfection in the compounds with smaller lanthanide ionic radii.