Effect of Ca substitution by Fe on the thermoelectric properties of Ca3Co4O9 ceramics |
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Authors: | F. Delorme P. Diaz-Chao F. Giovannelli |
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Affiliation: | 1.GREMAN UMR 7347 CNRS, CEA, INSA CVL, IUT de Blois,Université Fran?ois Rabelais de Tours,Blois Cedex,France;2.CRISMAT, UMR CNRS-ENSICAEN 6508,Caen,France;3.Materials Division,National Physical Laboratory,Middlesex,UK |
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Abstract: | (Ca1-xFex)3Co4O9 polycrystalline samples (x?=?0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1 and 0.2) have been prepared by solid state reaction and sintered by spark plasma sintering. Their thermoelectric properties have been studied between 323 and 1000 K. The substitution limit is low (< 3%). For higher iron contents, formation of Co3O4, Ca2FeCoO5 and a calcium ferrite compound occurs. Concerning electrical conductivity and power factor, an optimum value exists for x?=?0.03 substitution. This optimum power factor is circa 10% higher than the one of the unsubstituted sample. The optimum thermal diffusivity is measured for the sample with x?=?0.02 and is circa 9% lower than the one of the unsubstituted sample. Therefore, the dimensionless figure of merit ZT is finally increased by 14% for the (Ca0.98Fe0.02)3Co4O9 and (Ca0.97Fe0.03)3Co4O9 compositions. |
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