| Resumo: | Potassium-substituted SrFeO3-delta for possible application as oxygen evolution electrode in alkaline or molten salt media was prepared by mechanical activation and characterized by X-ray diffraction, dilatometric and thermogravimetric analysis, Mossbauer spectroscopy, and electrical conductivity measurements. Room temperature mechanical activation of a mixture of oxide precursors with subsequent thermal treatments at 700-900 degrees C results in the formation of Sr(0.9)Ka(0.1)FeO(3-delta) with tetragonal perovskite-like structure. Such allows to decrease the synthesis temperature, if compared to the conventional solid-state route, and to prevent possible volatilization of potassium. The results of Mossbauer spectroscopy studies indicate that the oxygen nonstoichiometry in the samples annealed in air at 900-1100 degrees C with subsequent rapid cooling vary in the range delta=0.30-0.32. The electrical conductivity in air exhibits a metal-like behaviour at temperatures above 400 degrees C and semiconductor behaviour in the low-temperature range, reaching 13-30 S/cm under prospective operation conditions for alkaline electrolyzers (<= 90 degrees C). (C) 2012 Elsevier Inc. All rights reserved.
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