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Author: search.filters.author.Harnwunggmoung, AdulSubject: search.filters.subject.Thermoelectric properties

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    Simultaneous Seebeck coefficient and electrical conductivity enhancement of GeSbTe films via Sn addition
    (2022-06-15)
    Khwansungnoen, Phalakorn
    ;
    Daichakomphu, Noppanut
    ;
    Sukwisute, Pisan
    ;
    Limsuwan, Pichet
    ;
    Somdock, Nuttakrit
    Sn-added GeSbTe (GST) thin films were deposited using a co-magnetron sputtering technique. The effects of varying the Sn content through a variable Sn target sputtering power and post annealing at 673 K were investigated. The DC power density applied to the GST target was controlled at 50 W, while the power density of the Sn target was increased from 0 W to 40 W. The results demonstrate the coexistence of the fcc-GST, hcp-GST and SnTe phases in the Sn-added GST thin films. The substitution of Sn at the Ge-site increases the crystallization speed and leads to defects and lattice disordered local arrangement in the GST films, causing the Seebeck coefficient to increase. The SnTe phase was created as a result of the high Sn content in the sample due to the over-doping limit of Sn into the GST structure. The presence of SnTe in Sn-doped GST films increased the electrical conductivity. The maximum power factor of 17.0 μW/cmK<sup>2</sup> at 450 K was obtained at an Sn content of 14.7 at%. These results indicated that the thermoelectric properties of Sn-doped GST films were improved via the formation of an appropriate amount of SnTe composite.
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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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    Achieving thermoelectric improvement through the addition of a small amount of graphene to CuAlO2 synthesized by solid-state reaction
    (2018-07-15)
    Daichakomphu, Noppanut
    ;
    Sakdanuphab, Rachsak
    ;
    Harnwunggmoung, Adul
    ;
    Pinitsoontorn, Supree
    ;
    Sakulkalavek, Aparporn
    In this work, delafossite CuAlO<inf>2</inf> powders with graphene (0.00–0.20 wt%) were synthesized by a solid-state reaction method. X-ray diffraction and transmission electron microscope results indicated that graphene was segregated in CuAlO<inf>2</inf> as a split phase, such as composite material. A little addition of graphene content reduces the thermal conductivity and increases the carrier concentration because the graphene generates many point defects and aided carrier-phonon scattering. The CuAlO<inf>2</inf> with graphene content of 0.05 wt% shows the maximum electrical conductivity of 470 S/m at 700 K. In addition, the maximum value for ZT of 0.0045 was recorded at 575 K with the graphene/CuAlO<inf>2</inf> composite (0.05 wt%). Therefore, in brief, this study has highlighted the benefits of combining delafossite CuAlO<inf>2</inf> with a small amount of graphene as a potential route for achieving highly efficient thermoelectric materials.