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    Item type:Publication,
    Effects of Pd substitution on the thermoelectric and electronic properties of delafossite Cu1-xPdxFeO2 (x=0.01, 0.03 and 0.05)
    (2014-07-01)
    Ruttanapun, Chesta
    Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> (x=0.01, 0.03 and 005) delafossite was prepared by solid state reactions and was calcined/sintered at 1050 °C. The effect of Pd<sup>2+</sup> substitution for the Cu<sup>1+</sup> sites on the thermoelectric and electronic properties of Cu <inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> were investigated. The crystal structure, oxygen decomposition, thermoelectric and electronic properties were characterized by X-ray diffraction, thermogravimetric analysis, X-ray photoelectron spectroscopy (XPS), Seebeck coefficient, electrical conductivity and thermal conductivity measurements. The characterization showed that Cu <inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> formed a hexagonal delafossite structure with R3-m symmetry. The existence of Pd<sup>2+</sup>, Cu<sup>1+</sup>, Cu<sup>2+</sup>, Fe<sup>3+</sup>, Fe<sup>4+</sup> and O was revealed from the XPS results. Confirmation of Pd<sup>2+</sup> substitution for the Cu <sup>1+</sup> sites occurred by increasing the c-axis in the lattice parameter with a Pd content. The O content intercalated at the center of the triangular Cu acted as a support to produce Cu<sup>2+</sup> ions and was reduced with an increasing Pd content. The mixed valencies of Cu<sup>1+</sup>/Cu<sup>2+</sup> and Cu<sup>1+</sup>/Pd<sup>2+</sup> in the Cu layer changed the electrical conductivity and the Fe<sup>3+</sup>/Fe<sup>4+</sup> mixed valencies in the FeO<inf>6</inf> layer caused the Seebeck coefficient to increase. Both the electrical conductivity and Seebeck coefficient for Pd contents of x=0.01 and 0.03 were higher than that of non-doped CuFeO<inf>2</inf>. The low thermal conductivity of Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> resulted from the substitution of Pd, which has a large atomic mass, into structure. The Jonker plot indicated that the electronic properties displayed a degenerate density of states and that Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> was a semiconductor. A high ZT value of 0.055 was obtained for a Pd content of 0.03 at 950 K. The Pd<sup>2+</sup> substitution for the Cu<sup>1+</sup> sites influenced the thermoelectric and electronic properties of the delafossite Cu<inf>(1-x)</inf>Pd<inf>(x)</inf>FeO<inf>2</inf> samples. © 2014 Elsevier Inc.
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    Optical and electronic transport properties of p-type CuCoO2 transparent conductive oxide
    (2013-09-18)
    Ruttanapun, Chesta
    ;
    Sa-Nguan-Cheep, Minraya
    ;
    Kahatta, Sagulthai
    ;
    Buranasiri, Prathan
    ;
    Jindajitawat, Phumin
    The CuCoO2 sample has been synthesized by a conventional solid-state reaction method to investigate electronic transport and optical properties for p-type transparent conducting oxide materials. The crystal structure was characterized by XRD. The Seebeck coefficient and electrical conductivity were measured in the high temperature. The UV-VIS-NIR and FTIR spectra were analyzed at room temperature. The XRD peaks confirm the samples forming the delafossite structure phase. The Seebeck coefficient sign confirms the samples displays the p-type conducting. The electronic transport energy for activating free carrier production and conduction contain 0.276 eV and 0.131 eV, respectively. The optical direct gap is 3.65 eV which is a visible-transparent oxide material. These results support that the CuCoO2 oxide compound is p-type transparent conducting oxide materials. © 2013 SPIE.