(Ln1.8Fe0.2)FeSbO7 (Ln = Pr–Tb) Mixed Oxides with the Pyrochlore Structure in CO Oxidation Reaction

— (Ln 1.8 Fe 0.2 )FeSbO 7 (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 mz ). The (Ln 1.8 Fe 0.2 )FeSbO 7 compounds have been shown to exhibit high activity for CO oxidation reaction. The best results have been obtained for (Pr 1.8 Fe 0.2 )FeSbO 7 , which has a 90% CO conversion temperature T 90 = 385°C. With increasing lanthanide atomic number, T 90 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.