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Title: Examination of the mechanism for the reversible aging behavior at open circuit when changing the operating temperature of (La 0.8Sr 0.2) 0.95 MnO 3 electrodes

The aging behavior of symmetrical cells, consisting of either (La 0.8Sr 0.2) 0.95 MnO 3 (LSM) or La 0.6Sr 0.4Co 0.2Fe 0.8O 3 (LSCF) electrodes screen printed on either 8 mol% yttria-stabilized zirconia (YSZ) or Ce 0.8Gd 0.2O 2 (GDC) electrolyte substrates, is reported as the symmetrical cell is thermally cycled between 700 °C and 800 °C. For LSM, between 700 °C and 850 °C, the polarization resistance exhibits slow increases or decreases with time (on the order of days) after a quick change in temperature. When increasing the temperature, the polarization resistance decreases with time, and when decreasing the temperature, the polarization resistance slowly increases with time. In a previous work, the authors had explained these results with LSM by connecting the testing conditions to literature reports of surface analysis of LSM thin films which demonstrated a change in the amount of surface cation segregation as a function of temperature. In this work, TEM/EDS/XPS analysis of dense LSM pellets thermally cycled under the same conditions as the symmetrical cells does not indicate any significant reversible change in the surface composition of the LSM pellet between 700 °C and 800 °C. An alternative hypothesis is proposed to explain the relationshipmore » between polarization resistance and the LSM cation/anion vacancy concentrations controlled by the Schottky reaction. The timescale of aging behavior is related to the time necessary for the cations to move to or from the LSM surface to adjust to the new equilibrium at each temperature. Furthermore, the relevance in understanding the mechanism behind the aging behavior is emphasized with respect to fuel cell sample/stack modeling as well as to proper testing procedures for reaching reliable conclusions when comparing different electrode samples.« less
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3]
  1. National Energy Technology Lab. (NETL), Morgantown, MW (United States); URS Corporation, Morgantown, MW (United States)
  2. National Energy Technology Lab. (NETL), Morgantown, MW (United States); West Virginia Univ., Morgantown, WV (United States)
  3. National Energy Technology Lab. (NETL), Morgantown, MW (United States)
Publication Date:
Report Number(s):
Journal ID: ISSN 0167-2738; PII: S0167273815000259
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Solid State Ionics
Additional Journal Information:
Journal Volume: 272; Journal Issue: C; Journal ID: ISSN 0167-2738
Research Org:
National Energy Technology Lab. (NETL), Albany, OR (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE)
Country of Publication:
United States
SOFC cathode; aging; LSM; cation; segregation; Schottky defect
OSTI Identifier: