ChemInform Abstract: Thermoelectric Properties of Ca₃Co₄O₉ Ceramics Prepared by an Alternative Pressure‐Less Sintering/Annealing Method.

Abstract

3Co4O9 (CCO) thermoelectric misfit layer cobaltite is prepared by double calcination of appropriate mixtures of CaCO3 and Co3O4 (900 C, 15 h) followed by pressureless sintering of pellets at 920 C (24 h). Alternatively, the mixture is fired in air (1000-1300 C, 6 h) and subsequently annealed at 900 C for 12, 24, and 72 h. Samples prepared using the latter route exhibit an increased conductivity compared to those sintered conventionally. This leads to an enhanced power factor of 170 W/(K 2 m) at 600 C. The thermal conductivity of 2.8 W/mK at 100 C is larger than that of porous and anisotropic conventionally sintered samples. The figure of merit of samples sintered with the proposed sintering/annealing process is ZT = 0.06 at 600 C. The process enables preparation of dense CCO ceramics as p-type component in thermoelectric generators. -(SCHULZ, T.; TOEPFER*, J.; J. Alloys Compd. 659 (2016) 122-126, http://dx.