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Author: search.filters.author.Thongkam, MontreeSubject: search.filters.subject.Agglomeration

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    Grain boundary, electrical transport and thermoelectric properties of the ultra-high rGO amount of C12A7-rGO composites
    (2024-04-30)
    Maneesai, Keerati
    ;
    Thongkam, Montree
    ;
    Sriwong, Chaval
    ;
    Ruttanapun, Chesta
    The Ca<inf>12</inf>Al<inf>14</inf>O<inf>33</inf> ceramic (C12A7) and reduced graphene oxide (rGO) composite which an ultra-high amount (i.e., 40, 50, 60, and 70 wt%) of rGO (ultra-high amount C12A7/rGO composite) were synthesized by a solid-state reaction process. After the hydraulic press, the heat treatment in the temperature range of 773 K under the argon environment had been performed with the composite pellets for 30 min. XRD results of the C12A7 and all the ultra-high amount C12A7/rGO composites indicated a pure phase of C12A7 ceramic. Raman spectra confirmed the existence of rGO content in all the ultra-high amount C12A7/rGO composites. Raman peaks also suggested reduction of the free O<inf>2</inf><sup>2−</sup> and O<inf>2</inf><sup>−</sup> ions from the framework of the ultra-high amount C12A7/rGO composites. SEM image presented the homogeneous grain boundary interface after the heat treatment at 773 K of the C12A7 wrapped by the rGO sheet, the agglomerated rGO sheet, and the rough interface stack of rGO sheets. UV-VIS spectroscopy presented the absorption behavior, direct energy gap, and indirect energy gap modifications of the ultra-high amount C12A7/rGO composites. Electrical conductivity of the ultra-high amount C12A7/rGO composites illustrated larger than 10<sup>8</sup> times improvement with temperature independence. Range of −5 to −17 μV/K, temperature dependence, and increased with rGO content increasing Seebeck coefficient were reported. Thermal conductivity of the ultra-high amount C12A7/rGO composites was increased with the rGO content increasing. Both the Power factor (PF) and the figure of merit (ZT) of the ultra-high amount C12A7/rGO composites were temperature dependent and were increased with the rGO content increasing, within the range of 0.4 μW/m.K<sup>2</sup> of PF and the range of 3x10<sup>−4</sup> of ZT, respectively. These experimental results verified grain boundary, modified energy band, electrical transport properties and thermoelectric properties of C12A7/rGO composites loading with ultra-high content rGO