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Phase Compatibility of the Thermoelectric Compounds in the Sr-Ca-Co-O System



Winnie K. Wong-Ng, Guangyao Liu, Joshua B. Martin, Evan L. Thomas, Nathan Lowhorn, James A. Kaduk


Two low-dimensional cobaltite series in the Sr-Ca-Co-O system have been investigated for their solid solution limit, structure, and compatibility phase relationships (850 deg C in air). Thermoelectric properties have been measured for selected members of these solid solutions. In (Ca, Sr)3Co4O9 which has a misfit layered structure, Sr was found to substitute in the Ca site to a limit of (Ca0.8Sr0.2)3Co4O9. Compounds in the homologous series, An+2ConCo O3n+3 (where A= Sr, Ca, (Ca,Sr) or (Sr,Ca)), consist of 1-dimensional parallel Co2O66- chains that are built from successive alternating face-sharing CoO6 trigonal prisms and n units of CoO6 octahedra along the hexagonal c-axis. In the Can+2ConCo O3n+3 series, only the n=1 phase (Ca3Co2O6 ) could be prepared under the present synthesis conditions. Sr substitutes in the Ca site of Ca3Co2O6 to a limit of (Ca0.9Sr0.1)3Co2O6. In the Srn+2ConCo O3n+3 series, Ca substitutes in the Sr site of the n = 2, 3 and 4 members to a limit of (Sr0.7Ca0.3)4Co3O9, (Sr0.67Ca0.33)5Co4O12, and (Sr0.725Ca0.275)6Co5O15, respectively. While the members of the Can+2ConCo O3n+3 and Srn+2ConCo O3n+3 series have reasonably high Seebeck coefficients and relatively low thermal conductivity, the electrical conductivity needs to be increased in order to achieve high ZT values.
Journal of Applied Physics


(Sr, Ca)-Co-O phase equilibira, Can+2ConCo O3n+3, Srn+2ConCo O3n+3, crystal structure, thermoelectric properties


Wong-Ng, W. , Liu, G. , Martin, J. , Thomas, E. , Lowhorn, N. and Kaduk, J. (2010), Phase Compatibility of the Thermoelectric Compounds in the Sr-Ca-Co-O System, Journal of Applied Physics, [online], (Accessed May 21, 2024)


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Created April 14, 2010, Updated February 19, 2017