Thermochemical expansion of mixed-conducting (Ba,Sr)Co_0.8Fe_0.2O_{3鈭?span style='font-style: italic'>未} ceramics

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• 作者：A.A. Yaremchenko ; S.M. Mikhalev ; E.S. Kravchenko ; J.R. Frade
• 关键词：Thermal expansion ; Chemical expansion ; Oxygen nonstoichiometry ; Membrane ; SOFC cathode
• 刊名：Journal of the European Ceramic Society
• 出版年：March, 2014
• 年：2014
• 卷：34
• 期：3
• 页码：703-715
• 全文大小：3320 K

文摘

The thermal and chemical expansion of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3鈭?em>未 (BSCF) and SrCo_0.8Fe_0.2O_3鈭?em>未 (SCF) mixed ionic-electronic conductors were studied in combination with oxygen nonstoichiometry (未) at 298-1223 K and p(O₂) = 10^鈭? to 1.00 atm. In order to minimize the effects of phase separation or oxygen-vacancy ordering processes, the data were collected in dynamic cooling mode using dense ceramic samples. The procedure was justified by a very fast equilibration at given p(O₂) in high-temperature range demonstrated for ceramics samples with different specific surface area. The difference in nonstoichiometry of BSCF and SCF at temperatures 鈮?73 K was found to be 鈮?.03 oxygen atoms per formula unit. BSCF demonstrates favorably smaller chemical expansion compared to SCF and many other mixed conductors, originating from smaller 未 variations and larger unit cell less sensitive to temperature and nonstoichiometry changes. Excessive thermochemical expansion impedes however the use of BSCF in single-phase fuel cell cathodes and planar mixed-conducting membranes.