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Title: Stability of solid oxide fuel cell materials

Chromite interconnection materials in an SOFC are exposed to both highly oxidizing conditions at the cathode and to highly reducing conditions at the anode. Because such conditions could lead to component failure, the authors have evaluated thermal, electrical, chemical, and structural stabilities of these materials as a function of temperature and oxygen partial pressure. The crystal lattice of the chromites was shown to expand for oxygen partial pressures smaller than 10{sup {minus}10} atm, which could lead to cracking and debonding in an SOFC. Highly substituted lanthanum chromite compositions were the most susceptible to lattice expansion; yttrium chromites showed better dimensional stability by more than a factor of two. New chromite compositions were developed that showed little tendency for lattice expansion under strongly reducing conditions, yet provided a good thermal expansion match to other fuel cell components. Use of these new chromite interconnect compositions should improve long-term SOFC performance, particularly for planar cell configurations. Thermodynamic properties of substituted lanthanum manganite cathode compositions have been determined through measurement of electromotive force as a function of temperature. Critical oxygen decomposition pressures for Sr and Ca-substituted lanthanum manganites were established using cells based on a zirconia electrolyte. Strontium oxide and calcium oxide activities inmore » a lanthanum manganite matrix were determined using cells based on strontium fluoride and calcium fluoride electrolytes, respectively. The compositional range of single-phase behavior of these ABO{sub 3}-type perovskites was established as a function of A/B cation ratios and the extent of acceptor doping. Before this work, very little thermodynamic information was in existence for substituted manganite compositions. Such information is needed to predict the long-term stability of solid oxide fuel cell assemblies.« less
Authors:
; ; ;  [1]
  1. Pacific Northwest National Lab., Richland, WA (United States) [and others
Publication Date:
OSTI Identifier:
458954
Report Number(s):
ORNL/FMP--96/1; CONF-9605167--
ON: DE97050349; TRN: 97:001933-0022
DOE Contract Number:
AC06-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: 10. annual conference on fossil energy materials, Knoxville, TN (United States), 14-16 May 1996; Other Information: PBD: Aug 1996; Related Information: Is Part Of Proceedings of the tenth annual conference on fossil energy materials; Cole, N.C.; Judkins, R.R. [comps.]; PB: 551 p.
Research Org:
Oak Ridge National Lab., TN (United States)
Country of Publication:
United States
Language:
English
Subject:
30 DIRECT ENERGY CONVERSION; CHROMIUM OXIDES; STABILITY; LANTHANUM OXIDES; MANGANESE OXIDES; SOLID ELECTROLYTE FUEL CELLS; CRACK PROPAGATION; ELECTRIC CONTACTS; TESTING