The effect of element substitution on high-temperature thermoelectric properties of Ca{sub 3}Co{sub 2}O{sub 6} compounds

• Published in: Journal of solid state chemistry Vol. 178; no. 5
• Main Authors: Mikami, Masashi, Funahashi, Ryoji, CREST, Japan Science and Technology Agency, 4-1-8, Honcho Kawaguchi, Saitama 332-0012
• Format: Journal Article
• Language: English
• Published: United States 15.05.2005
• Subjects: CALCIUM COMPOUNDS; CARRIER DENSITY; COBALT COMPOUNDS; COPPER COMPOUNDS; ELECTRIC CONDUCTIVITY; GRAIN BOUNDARIES; GRAIN SIZE; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; IRON COMPOUNDS; MANGANESE COMPOUNDS; NICKEL COMPOUNDS; OXIDES; POLYCRYSTALS; SOLIDS; THERMOELECTRIC PROPERTIES
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1016/j.jssc.2005.03.004

Polycrystalline Ca{sub 3}Co{sub 1.8}M{sub 0.2}O{sub 6} (M=Mn, Fe, Co, Ni, Cu) and Ca{sub 2.7}Na{sub 0.3}Co{sub 2}O{sub 6} were synthesized by solid-state reaction to evaluate the effect of substitution on the thermoelectric properties of Ca{sub 3}Co{sub 2}O{sub 6}. Substitution by Mn, Cu and Na appears to increase carrier density, given that electrical resistivity ({rho}) and the Seebeck coefficient (S) were simultaneously reduced. Conversely, Fe substitution seems to reduce carrier density, resulting in a simultaneous increase in S and {rho}. Cu and Na substitution resulted in a significant decrease in {rho} due to enhancement of grain size and grain boundary connectivity, which could have a strong impact on {rho}. Not only the intrinsic substitution effect on the electronic state but also this modification of the microstructure plays an important role in improvement of the thermoelectric power factor, particularly in the case of the Na-substituted sample.