Enhanced thermoelectric performance of Ca 3 Co 4 O 9 doped with aluminum
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Enhanced thermoelectric performance of Ca3Co4O9 doped with aluminum M. A. Mohammed1,3, M. B. Uday1,2, and S. Izman1,* 1
School of Mechanical Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Johor Baharu, Malaysia Centre for Advanced Composite Materials, Institute for Vehicle Systems and Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor, Malaysia 3 Department of Materials Engineering, College of Engineering, University of Basrah, Basrah, Iraq 2
Received: 9 April 2020
ABSTRACT
Accepted: 8 August 2020
Ca3-x AlxCo4O9 polycrystalline ceramics with a small amount of Al (0 B x B 0.4) were fabricated using the sol–gel combustion method with natural starch as a fuel. All synthesized samples were a pure phase with no Al-based secondary phase detected, and a defect-free lattice structure. Their diffraction peaks shifted to higher angle values as doping (x) increased. A mixture of valence states of Co2?, Co3?, and Co4? were detected in all samples. In the Ca3Co4O9 system, both the Seebeck coefficient and the thermal conductivity are enhanced by a single doping of Al. The maximum power factor (0.348 mW/ m K2) and figure of merit (0.14) was obtained for x = 0.1 at 700 K; these values are respectively 3.6% and 28.4% higher than undoped samples. These results indicate that Al is a promising doping element for enhancing the thermoelectric properties of the Ca3Co4O9 system.
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction Thermoelectric (TE) materials are characterized by a Seebeck coefficient capable of transforming heat into electrical energy. They are non-polluting, long lasting, have non-moveable components and high reliability [1]. To generate electricity, excellent TE materials must be highly efficient at converting heat to electrical energy. Typical real world potential applications for TE materials are recycling waste heat from vehicle exhaust systems and other industrial waste heat to save energy [2]. The ideal materials for thermoelectric applications need a high Seebeck by
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https://doi.org/10.1007/s10854-020-04212-x
producing high voltage, fading electrical resistivity (q) by lowering the Joule heating, and dim thermal conductivity (j) for preserving the heat at the ends to achieve an excellent ZT = S2T/qj [3]. Therefore, this technology can assist in countering the effects of climate change by reducing fossil fuel consumption and lowering the quantity of CO2 released. Indeed, thermoelectric generating and cooling materials are upand-coming applications for improved energy consumption [4]. The latest commercial applications have drawn attention to intermetallic thermoelectric materials (e.g., Bi2Te3, CoSb3) that are capable of superior
J Mater Sci: Mater Electron
thermoelectric performance at reduced temperatures [5, 6]. Among thermoelectric generators, the materials that show particular potential are metal oxides. These materials are advantageous, because they can be employed in applicati
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