Details
| Original language | English |
|---|---|
| Pages (from-to) | 5851-5858 |
| Number of pages | 8 |
| Journal | Chemistry of Materials |
| Volume | 20 |
| Issue number | 18 |
| Early online date | 29 Aug 2008 |
| Publication status | Published - 23 Sept 2008 |
Abstract
The mixed ionic-electronic conductor (MEC) (Ba0.5Sr 0.5)(Co0.8Fe0.2)O3-δ (BSCF) is a renowned material with applications in membrane reactors and as cathodes in solid-oxide fuel cells. Despite BSCF's large oxygen permeabilities, long-time phase instability at intermediate temperatures has been reported. However, the mechanism of this decomposition is still unclear. Here, we present a study of the synthesis of BSCF and compare our results with those obtained from long-time decomposition. Rietveld and Le Bail analysis as well as transmission electron microscopy studies were applied to investigate the reaction sequence in BSCF formation. We are now able to draw the following conclusion about the reaction mechanism: the formation as well as decomposition is due to a reversible reordering of the hexagonal AO3-layer stacking sequence in the cubic perovskite, which can occur if the cubic BSCF is kept at temperatures below T = 1173 K for long time periods, thereby leading to the decomposition of BSCF into a three-phase mixture. The driving force for this reaction was identified to occur at the cobalt site because cobalt prefers a low-spin configuration in the 3+ oxidation state. This reaction occurs only at temperatures below T = 1173 K because of the oxidation of cobalt at low temperatures.
ASJC Scopus subject areas
- Chemistry(all)
- General Chemistry
- Chemical Engineering(all)
- General Chemical Engineering
- Materials Science(all)
- Materials Chemistry
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In: Chemistry of Materials, Vol. 20, No. 18, 23.09.2008, p. 5851-5858.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Correlation of the formation and the decomposition process of the BSCF perovskite at intermediate temperatures
AU - Arnold, Mirko
AU - Gesing, Thorsten M.
AU - Martynczuk, Julia
AU - Feldhoff, Armin
PY - 2008/9/23
Y1 - 2008/9/23
N2 - The mixed ionic-electronic conductor (MEC) (Ba0.5Sr 0.5)(Co0.8Fe0.2)O3-δ (BSCF) is a renowned material with applications in membrane reactors and as cathodes in solid-oxide fuel cells. Despite BSCF's large oxygen permeabilities, long-time phase instability at intermediate temperatures has been reported. However, the mechanism of this decomposition is still unclear. Here, we present a study of the synthesis of BSCF and compare our results with those obtained from long-time decomposition. Rietveld and Le Bail analysis as well as transmission electron microscopy studies were applied to investigate the reaction sequence in BSCF formation. We are now able to draw the following conclusion about the reaction mechanism: the formation as well as decomposition is due to a reversible reordering of the hexagonal AO3-layer stacking sequence in the cubic perovskite, which can occur if the cubic BSCF is kept at temperatures below T = 1173 K for long time periods, thereby leading to the decomposition of BSCF into a three-phase mixture. The driving force for this reaction was identified to occur at the cobalt site because cobalt prefers a low-spin configuration in the 3+ oxidation state. This reaction occurs only at temperatures below T = 1173 K because of the oxidation of cobalt at low temperatures.
AB - The mixed ionic-electronic conductor (MEC) (Ba0.5Sr 0.5)(Co0.8Fe0.2)O3-δ (BSCF) is a renowned material with applications in membrane reactors and as cathodes in solid-oxide fuel cells. Despite BSCF's large oxygen permeabilities, long-time phase instability at intermediate temperatures has been reported. However, the mechanism of this decomposition is still unclear. Here, we present a study of the synthesis of BSCF and compare our results with those obtained from long-time decomposition. Rietveld and Le Bail analysis as well as transmission electron microscopy studies were applied to investigate the reaction sequence in BSCF formation. We are now able to draw the following conclusion about the reaction mechanism: the formation as well as decomposition is due to a reversible reordering of the hexagonal AO3-layer stacking sequence in the cubic perovskite, which can occur if the cubic BSCF is kept at temperatures below T = 1173 K for long time periods, thereby leading to the decomposition of BSCF into a three-phase mixture. The driving force for this reaction was identified to occur at the cobalt site because cobalt prefers a low-spin configuration in the 3+ oxidation state. This reaction occurs only at temperatures below T = 1173 K because of the oxidation of cobalt at low temperatures.
UR - http://www.scopus.com/inward/record.url?scp=53549124414&partnerID=8YFLogxK
U2 - 10.1021/cm801463h
DO - 10.1021/cm801463h
M3 - Article
AN - SCOPUS:53549124414
VL - 20
SP - 5851
EP - 5858
JO - Chemistry of Materials
JF - Chemistry of Materials
SN - 0897-4756
IS - 18
ER -