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Volume texture and anisotropic thermoelectric properties in Ca3Co4O9 bulk materials

Abstract : Ca3Co4O9 lamellar thermoelectric (TE) oxides are potentially suitable for energy conversion applications at high temperature in air. To be used in TE devices, bulk Ca3Co4O9 materials must possess large texture strengths to attain the optimal TE performances, and sufficient material size to fabricate TE ceramic elements (legs). This paper reports the development of thick Ca3Co4O9 multilayer samples by hot-pressing a stack of dense and strongly textured Ca3Co4O9 bulk single-layer samples along their mean c*-axis. The volume texture was investigated by using the neutron diffraction method, and revealed the largest strength achieved hitherto in such materials. The Seebeck coefficient, S, electrical resistivity, rho, and thermal conductivity, kappa, were determined parallel (S-c, rho(c), kappa(c)) and perpendicular (S-ab, rho(ab), kappa(ab)) to the mean c*-axis. rho and kappa were found to be highly anisotropic, with ratios rho(c)/rho(ab) = 8.8 and kappa(ab)/kappa(c) = 2.7 at 900 K, respectively. S unexpectedly depicted an anisotropic character as well, but it remains less prominent. The power factor, PF, and figure-of-merit, ZT, were hence anisotropic, exhibiting respective ratios PFab/PFc = 12 and ZT(ab)/ZT(c) = 4.6. The ZT(ab) value reached 0.16 at 900 K which is 2 fold the one of conventionally sintered materials.
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Submitted on : Tuesday, March 1, 2016 - 10:47:29 AM
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Driss Kenfaui, Daniel Chateigner, Moussa Gomina, Jacques G. Noudem, Bachir Ouladdiaf, et al.. Volume texture and anisotropic thermoelectric properties in Ca3Co4O9 bulk materials. Materials Today: Proceedings, Elsevier, 2015, 2 (2), pp.637-646. ⟨10.1016/j.matpr.2015.05.089⟩. ⟨hal-01280797⟩



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