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A3: High temperature materials

Anisotropy of thermoelectric figure of merit (ZT) in textured Ca3Co4O9 specimens prepared by spark plasma sintering process

Chang-Hyun Lim 1,2, Soon-Mok Choi3,*, Won-Seon Seo1, Kyu Hyoung Lee4, Soonil Lee1, Young Soo Lim1, Jong-Young Kim1, and Hyung-Ho Park 2
1 KICET, Korea2 Yonsei University, Korea3 Koreatech, Korea4 Kangwon National Univ., Korea 

Textured Ca3Co4O9 ceramics were prepared by spark plasma sintering from commercial CaCO3 and Co3O4 powders. We investigated the microstructure of the specimens and the orientation of the textured specimens was evaluated by Lotgering factor method. The results showed that spark plasma sintering (SPS) was an effective technology to prepare textured Ca3Co4O9 ceramics. Thermoelectric anisotropy of the textured specimens was investigated. Both the power factors thermal conductivities were measured in two different directions respectively: along the direction parallel and perpendicular to the pressing direction. The anisotropy of the electrical conductivity was larger than the thermal conductivity in the textured Ca3Co4O9 ceramics because of the different grain boundary scattering characteristics. The maximum ZT value along the direction perpendicular to the pressing direction was more than 20% higher than the case of the parallel direction.