Kenfaui, Driss, Lenoir, Bertrand, Chateigner, Daniel, Ouladdiaf, Bachir, Gomina, Moussa, and Noudem, Jacques Guillaume
Abstract: Multilayer Ca3Co4O9 (349) thick thermoelectric (TE) materials were fabricated by hot-pressing stacked dense and strongly textured single-layer samples. Microstructure and volume quantitative texture investigations were undertaken by using scanning electron microscopy and neutron diffraction techniques, respectively. The results show a bulk density similar to single-layer samples, but remarkable texture strength reinforcement. The electrical resistivity, ρ, and Seebeck coefficient, S, were reproducibly measured in directions parallel (ρ c and S c ) and perpendicular (ρ ab and S ab ) to the mean c-axis. ρ showed a high anisotropy ratio of 13.5 and 8.8 at 300 and 900K, respectively, and ρ ab kept the same values whereas ρ c decreased in the multilayer samples. S ab and S c unexpectedly revealed different values. The thermal conductivity also displayed a significant anisotropy, with ratio at 900K. The resulting figure-of-merit ZT is then noticeably anisotropic, with ratio . ZT ab was found 2 times larger than ZT value of the conventional sintered 349 materials often used for TE modules fabrication. [Copyright &y& Elsevier]