Mixed oxygen ion/electron-conducting ceramics for oxygen separation

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Solid mixed-conducting electrolytes in the series La{sub l-x}A{sub x}Co{sub l-y}Fe{sub y}O{sub 3-{delta}} (A = Sr,Ca,Ba) are potentially useful as passive membranes to separate high purity oxygen from air and as cathodes in fuel cells. All of the compositions studied exhibited very high electrical conductivities. At lower temperatures, conductivities increased with increasing temperature, characterized by activation energies of 0.05 to 0.16 eV that are consistent with a small polaron (localized electronic carrier) conduction mechanism. At higher temperatures, electronic conductivities tended to decrease with increasing temperature, which is attributed to decreased electronic carrier populations associated with lattice oxygen loss. Oxygen ion conductivities ... continued below

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11 p.

Creation Information

Stevenson, J.W.; Armstrong, B.L.; Armstrong, T.R.; Bates, J.L.; Pederson, L.R. & Weber, W.J. May 1, 1995.

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  • Pacific Northwest Laboratory
    Publisher Info: Pacific Northwest Lab., Richland, WA (United States)
    Place of Publication: Richland, Washington

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Solid mixed-conducting electrolytes in the series La{sub l-x}A{sub x}Co{sub l-y}Fe{sub y}O{sub 3-{delta}} (A = Sr,Ca,Ba) are potentially useful as passive membranes to separate high purity oxygen from air and as cathodes in fuel cells. All of the compositions studied exhibited very high electrical conductivities. At lower temperatures, conductivities increased with increasing temperature, characterized by activation energies of 0.05 to 0.16 eV that are consistent with a small polaron (localized electronic carrier) conduction mechanism. At higher temperatures, electronic conductivities tended to decrease with increasing temperature, which is attributed to decreased electronic carrier populations associated with lattice oxygen loss. Oxygen ion conductivities were higher than that of yttria stabilized zirconia and increased with the cobalt content and also increased with the extent of divalent A-site substitution. Thermogravimetric studies were conducted to establish the extent of oxygen vacancy formation as a function of temperature, oxygen partial pressure, and composition. These vacancy populations strongly depend on the extent of A-site substitution. Passive oxygen permeation rates were established for each of the compositions as a function of temperature and oxygen partial pressure gradient. For 2.5 mm thick membranes in an oxygen vs nitrogen partial pressure gradient, oxygen fluxes at 900 C ranged from approximately 0.3 sccm/cm{sup 2} for compositions high in iron and with low amounts of strontium A-site substitution to approximately 0.8 sccm/cm{sup 2} for compositions high in cobalt and strontium. A-site substitution with calcium instead of strontium resulted in substantially lower fluxes.

Physical Description

11 p.

Notes

OSTI as DE95014181

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  • 9. annual conference on fossil energy materials, Oak Ridge, TN (United States), 16-18 May 1995

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  • Other: DE95014181
  • Report No.: PNL-SA--26373
  • Report No.: CONF-9505204--9
  • Grant Number: AC06-76RL01830
  • Office of Scientific & Technical Information Report Number: 102491
  • Archival Resource Key: ark:/67531/metadc625979

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  • May 1, 1995

Added to The UNT Digital Library

  • June 16, 2015, 7:43 a.m.

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  • April 7, 2016, 4:44 p.m.

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Stevenson, J.W.; Armstrong, B.L.; Armstrong, T.R.; Bates, J.L.; Pederson, L.R. & Weber, W.J. Mixed oxygen ion/electron-conducting ceramics for oxygen separation, article, May 1, 1995; Richland, Washington. (digital.library.unt.edu/ark:/67531/metadc625979/: accessed August 19, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.