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Author: search.filters.author.Charoenphakdee, AnekSubject: search.filters.subject.Thermoelectric properties

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    Effect of Strong Correlation of Mg2+-doped into Cr3+ Sites of CuCrO2 on Thermoelectric Properties
    (2015-09-02)
    Ruttanapun, Chesta
    ;
    Charoenphakdee, Anek
    ;
    Nisoa, Mudtorlep
    ;
    Muthitamongkol, Pennapa
    ;
    Thanachayanont, Chanchana
    This study aims to investigate the strong correlation effect of spin and charge carriers for the Mg<sup>2+</sup>-substituted into Cr<sup>3+</sup> sites of CuCrO2 delafossite on thermoelectric properties. The CuCr0.98Mg0.02O2 sample was synthesized by a solid state reaction. The starting powder CuO, Cr2O3 and MgO were ball milled with poly vinyl alcohol solution for 24 h. The ball milled powder was pressed and sintered in air atmosphere at temperature 1050 C for 6 h. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured at high temperature. The XRD displayed peaks of the pure phase CuCrO2 structure as hexagonal delafossite-type structure space group: Rm. The Seebeck coefficient of the samples displayed positive sign as p-type (hole) conductor. The XPS results displayed Mg<sup>2+</sup>, Cu<sup>1+</sup>, Cr<sup>3+</sup> and Cr<sup>4+</sup> ion states. The Mg<sup>2+</sup> induced mixed-valance Cr<sup>3+</sup>/Cr<sup>4+</sup> states resulting in enhanced Seebeck coefficient due to a strong correlation of the spin-entropy. The experimental results of Seebeck value were close to calculated results by the extended Heikes formula confirming of the strong correlation effect. In addition, the Mg-doped CuCrO2 resulted in increased electrical conductivity and reduced thermal conductivity with increasing temperature. These indicate that the Mg<sup>2+</sup>-substituted for Cr<sup>3+</sup> of CuCrO2 delafossite enhance the thermoelectric properties. © 2015
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    Thermoelectric properties of Sn2+-substituted CuFeO2 delafossite-oxide
    (2013-10-29)
    Ruttanapun, Chesta
    ;
    Jindajitawat, Phumin
    ;
    Thowladda, Warawoot
    ;
    Neeyakorn, Worakarn
    ;
    Thanachayanont, Chanchana
    This study aims to investigate the effect of the Sn<sup>2+</sup>-substituted into the CuFeO<inf>2</inf> delafossite on thermoelectric properties in the Sn content of x = 0.03, 0.05. The CuFe<inf>1-x</inf>Sn<inf>x</inf>O<inf>2</inf> samples were synthesized by solid state reaction. The crystal structure was characterized by XRD, TGA, XPS and the thermoelectric properties were measured in the range of 300 to 960 K. The Seebeck coefficient display positive sign in all temperature range and the XPS show the stable Sn<sup>+2</sup> state as confirming the Sn-doped CuFeO<inf>2</inf> playing p-type conductor. The Sn<sup>2+</sup>-substituted supports the mixed valency Fe<sup>3+</sup>/Fe<sup>4+</sup> state in transition octahedral oxide of FeO<inf>6</inf> layer enhancing Seebeck coefficient. The high Seebeck are appeared in content of x=0.03 which are 280 to 340 μV/K in the range of 300 to 800 K. The experimental Seebeck corresponds to the prediction formula at high temperature. Totally, the maximum Power Factor is 2.30×10<sup>-4</sup> W/mK<sup>2</sup> occurring in the CuFe<inf>0.95</inf>Sn<inf>0.05</inf>O<inf>2</inf> at 860 K which is higher than that value of the undoped-CuFeO<inf>2</inf> in 4 times. These support that the Sn-substituted CuFeO<inf>2</inf> delafossite enhancing thermoelectric properties. © (2013) Trans Tech Publications, Switzerland.
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    Thermoelectric properties of Cu1-xPtxFeO2 (0.0 ≤ x ≤ 0.05) delafossite-type transition oxide
    (2011-03-31)
    Ruttanapun, Chesta
    ;
    Wichainchai, Aree
    ;
    Prachamon, Wutthisak
    ;
    Yangthaisong, Anucha
    ;
    Charoenphakdee, Anek
    The samples of Cu<inf>1-x</inf>Pt<inf>x</inf>FeO<inf>2</inf> (0 ≤ x ≤ 0.05) delafossite were synthesized by solid state reaction method for studying thermoelectric properties. The properties of Seebeck coefficient, electrical conductivity and thermal conductivity were measured in the high temperature ranging from 300 to 960 K. The results of Seebeck coefficient, electrical conductivity and power factor were increased with increasing Pt substitution and temperature. The thermal conductivity was decreased from 5.8 to 3.5 W/mK with increasing the temperature from 300 to 960 K. An important results, the highest value of power factor and ZT is 2.0 × 10<sup>-4</sup> W/mK<sup>2</sup> and 0.05, respectively, for x = 0.05 at 960 K. © 2011 Elsevier B.V. All rights reserved.