Synthesis of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} electrocatalysts by mechanical activation

Journal Article · Fri Feb 15 00:00:00 EST 2013 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2012.10.009· OSTI ID:22150014

Waerenborgh, J. C. ^[1]; Kovalevsky, A. V.; Yaremchenko, A. A.; Frade, J. R. ^[2]

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1. UCQR, IST/ITN, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, CFMC-UL, Sacavem 2686-953 (Portugal)
2. Department of Materials and Ceramics Engineering, CICECO, University of Aveiro, Aveiro 3810-193 (Portugal)

Potassium-substituted SrFeO{sub 3-{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, Moessbauer spectroscopy, and electrical conductivity measurements. Room temperature mechanical activation of a mixture of oxide precursors with subsequent thermal treatments at 700-900 Degree-Sign C results in the formation of Sr{sub 0.9}K{sub 0.1}FeO{sub 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 Moessbauer spectroscopy studies indicate that the oxygen nonstoichiometry in the samples annealed in air at 900-1100 Degree-Sign 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 Degree-Sign C and semiconductor behaviour in the low-temperature range, reaching 13-30 S/cm under prospective operation conditions for alkaline electrolyzers ({<=}90 Degree-Sign C). - graphical abstract: XRD patterns of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} powders, as-prepared and after annealing at different temperatures. Log({sigma}{center_dot}T) vs. 1000/T plot of the electrical conductivity of Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}}. The inset shows the thermal variation of {sigma}. Ceramics used were prepared by mechanical activation followed by a two-step sintering process at 900 Degree-Sign C for 1 h and 1000 Degree-Sign C for 5 h (82% densification). Highlights: Black-Right-Pointing-Pointer Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} was successfully obtained by mechanical activation of oxide precursors. Black-Right-Pointing-Pointer Synthesis temperature is significantly lower when compared to a conventional solid-state route. Black-Right-Pointing-Pointer Oxygen nonstoichiometry of annealed samples at 900-1100 Degree-Sign C vary in the range {delta}=0.30-0.32. Black-Right-Pointing-Pointer Sr{sub 0.9}K{sub 0.1}FeO{sub 3-{delta}} shows metal and semiconductor behaviour above and below 400 Degree-Sign C, respectively.

• OSTI ID: 22150014
• Journal Information: Journal of Solid State Chemistry, Vol. 198; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
ANNEALING
CERAMICS
ELECTRIC CONDUCTIVITY
ELECTROCATALYSTS
FERRITE
FERRITES
MOESSBAUER EFFECT
MOLTEN SALTS
OXIDES
OXYGEN
PEROVSKITE
POTASSIUM
POWDERS
SEMICONDUCTOR MATERIALS
SOLIDS
STRONTIUM
SYNTHESIS
THERMAL GRAVIMETRIC ANALYSIS
X-RAY DIFFRACTION