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Author: search.filters.author.Gaewdang, ThitinaiSubject: search.filters.subject.Seebeck coefficient

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    Influence of Na doping on the thermoelectric properties of CuAlO2 delafossite
    (2014-01-01)
    Wongcharoen, Ngamnit
    ;
    Gaewdang, Thitinai
    The polycrystalline Na-doped CuAlO<inf>2</inf> ceramics were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al<inf>2</inf>O<inf>3</inf> and NaNO<inf>3</inf>·6H<inf>2</inf>O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1,423 K for 24 h. XRD patterns showed the crystal structure of the as-sintered Cu<inf>1-x</inf>Na<inf>x</inf>AlO<inf>2</inf> (0≤x≤0.05) belonging to rhombohedral, space group R3m along with the CuO and CuAl<inf>2</inf>O<inf>4</inf> phases. The minimum resistivity value around 4.48x10<sup>2</sup> Ω ·cm and maximum hole concentration around 2.04x10<sup>16</sup> cm<sup>-3</sup> were observed for x=0.03 at room temperature. The properties of Seebeck coefficient and electrical resistivity were measured in the high temperature ranging 300 to 700 K. The results of electrical resistivity, Seebeck coefficient and power factor values decrease with increasing Na content. The calculated activation energy of conductivity (in the range of 160-250 meV) is larger than that of thermopower (in the range of 26-83 meV) which suggests that the conduction mechanism may be determined as a small polaron hopping type. © (2014) Trans Tech Publications, Switzerland.
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    Structural and thermoelectric properties of zn-doped cuprous aluminate delafossite
    (2013-10-04)
    Wongcharoen, Ngamnit
    ;
    Gaewdang, Thitinai
    ;
    Wongcharoen, Tiparatana
    The polycrystalline Zn-doped CuAlO<inf>2</inf> ceramics were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al<inf>2</inf>O<inf>3</inf> and Zn(CH<inf>3</inf>COO) <inf>2</inf>{dot operator}2H<inf>2</inf>O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1,150 °C for 24 h. XRD patterns showed the crystal structure of the as-sintered CuAl<inf>1-x</inf>Zn<inf>x</inf>O<inf>2</inf> (0≤x≤0.05) belonging to rhombohedral, space group R3m along with the CuO and CuAl2O4 phases. From SEM micrographs, the grain size slightly decreases when the amount of Zn in CuAl<inf>1-x</inf>Zn<inf>x</inf>O<inf>2</inf> samples increases. Hall mobility and hole concentration of the as-sintered samples were obtained from Hall effect measurements in van der Pauw configuration at room temperature. The electrical resistivity measurements as a function of temperature were performed. The variation of Seebeck coefficient and power factor as a function of temperature was also investigated. In the present study, the Zndoped CuAlO<inf>2</inf> ceramics probably have advantages for use in high temperature thermoelectric devices. © (2013)Trans Tech Publications,Switzerland.
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    Thermoelectric properties of Ni-doped CuAlO2
    (2009-01-01)
    Wongcharoen, Ngamnit
    ;
    Gaewdang, Thitinai
    The polycrystalline Ni-doped CuAlO<inf>2</inf> were obtained by solid state reaction method. The mixture of high purity grade of CuO, Al<inf>2</inf>O <inf>3</inf> and Ni(NO<inf>3</inf>)<inf>2</inf>.6H<inf>2</inf>O powders was ground and then pressed by using uniaxial pressure. The obtained pellet was sintered in air at 1423 K for 24 h. XRD patterns showed the crystal structure of the as-sintered CuAl<inf>1-x</inf>Ni<inf>x</inf>O<inf>2</inf> (0≤ x ≤0.10) belonging to rhombohedral, space group. No evidence of second phase was observed when Ni doping up to x = 0.01. At Ni content x ≥ 0.01 CuAl <inf>1-x</inf>Ni<inf>x</inf>O<inf>2</inf> solid solution phase along with the CuO and CuAl<inf>2</inf>O<inf>4</inf> phases were observed. From SEM micrographs, the grain size decreased from 6 to 2 μm when the amount of Ni in CuAl<inf>1-x</inf>Ni<inf>x</inf>O<inf>2</inf> samples increased. Hall mobility and hole concentration of the as-sintered samples were obtained from Hall effect measurements at room temperature. The activation energy values deduced from the electrical resistivity measurements as a function of temperature were reported. The variation of Seebeck coefficient and power factor as a function of temperature was also investigated. From the experimental results, the substitution of Ni<sup>2+</sup> ion in Cu<sup>+</sup> site of CuAl <inf>1-x</inf>Ni<inf>x</inf>O<inf>2</inf> material may be drawn. © 2009 Elsevier B.V. All rights reserved.