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Author: search.filters.author.Chanlek, NarongSubject: search.filters.subject.Fe doped

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    Figure of merit improvement of delafossite CuAlO2 with the addition of Fe and graphene
    (2019-11-01)
    Daichakomphu, Noppanut
    ;
    Harnwunggmoung, Adul
    ;
    Chanlek, Narong
    ;
    Sakdanuphab, Rachsak
    ;
    Sakulkalavek, Aparporn
    This study investigated the synthesis of delafossite CuAlO<inf>2</inf> with Fe and graphene through a solid-state reaction method. The results of X-ray diffractometry showed that graphene was insoluble in delafossite CuAlO<inf>2</inf> while Fe was substituted into Al sites, expanding the d-spacing. From X-ray photoelectron spectroscopy, graphene induced excess oxygen in the delafossite CuAlO<inf>2</inf> structure via C–O–Cu bonds and improved the electrical conductivity. In addition, the thermal conductivity was reduced due to generation of point defects, phonon-phonon Umklapp and carrier-phonon scattering. The addition of Fe and graphene in CuAlO<inf>2</inf> shows an improvement of ZT to 0.0114 at 573 K. This is attributable to its increase in charge carrier density, as well as a decrease in thermal conductivity. This study highlights the benefits of combining Fe and graphene in delafossite CuAlO<inf>2</inf> as a prospective process for attaining a high figure of merit thermoelectric materials.
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    Enhanced carrier concentration of Fe doped delafossite CuAlO2 by double-effect: Divalent metal ions doping and excess oxygen
    (2018-12-15)
    Daichakomphu, Noppanut
    ;
    Sakdanuphab, Rachsak
    ;
    Harnwunggmoung, Adul
    ;
    Puarporn, Yingyot
    ;
    Chanlek, Narong
    Bulk CuAlO<inf>2</inf> compound has been widely studied as a p-type metal oxide semiconductor material due to the simplicity in its synthesis and use of inexpensive raw materials. The Fe doping in CuAlO<inf>2</inf> has been demonstrated to enhance the electrical conductivity. An in-depth analysis of the effect of Fe doping in CuAlO<inf>2</inf> on the carrier concentration improvement was revealed. Delafossite CuAl<inf>1−x</inf>Fe<inf>x</inf>O<inf>2</inf> powders with x = 0.00, 0.05, 0.10, 0.15, 0.20 and 0.30 were synthesized by a solid-state reaction method. The X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) studies were used to measure the atomic-ion concentrations and the oxidation state of each element. The variations of carrier concentration corresponded with a ratio of Cu<sup>2+</sup>/Cu<sup>1+</sup> in CuAlO<inf>2</inf>. We found that the increase of Cu<sup>2+</sup>/Cu<sup>1+</sup> was caused by double effects through divalent metal ions (Fe<sup>2+</sup>) doping and excess oxygen (O<inf>2−δ</inf>) in CuAlO<inf>2</inf>. The maximum carrier concentration of 8.09 × 10<sup>17</sup> cm<sup>−3</sup> was obtained for the CuAlO<inf>2</inf> sample at Fe content of 10 at.%.