Sakulkalavek, Aparporn

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Sakulkalavek, Aparporn
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Sakulkalavek, A.
Sakulkalavek, Aparpron
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Email
aparporn.sa@kmitl.ac.th

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    Energy-saving synthesis and β-phase enhancement of Cu2Se thermoelectric materials via the microwave hybrid heating technique
    (2021-10-25)
    Rudradawong, Chalermpol
    ;
    Sukwisute, Pisan
    ;
    Limsuwan, Pichet
    ;
    Harnwunggmoung, Adul
    ;
    Horprathum, Mati
    Thermoelectric generators harvest energy from waste heat and convert it to electricity. β-Cu<inf>2</inf>Se is a candidate for them due to its outstanding thermoelectric properties and its environmentally friendly component elements. A microwave hybrid heating (MHH) method was used for the fast synthesis and enhancement of β-Cu<inf>2</inf>Se materials. The effects of the MHH reaction time on the phase microstructure and thermoelectric properties of the Cu<inf>2</inf>Se material were investigated, and the MHH method was compared with the conventional heating method. The X-ray diffraction patterns of samples, synthesized via the MHH method, showed monoclinic- (α) and cubic- (β) Cu<inf>2</inf>Se crystalline structures, whereas a single monoclinic-(α) structure was identified in a sample, synthesized via a conventional heating method. In addition, the β-Cu<inf>2</inf>Se phase was enhanced with increased MHH reaction time. The carrier concentration increased with β-Cu<inf>2</inf>Se content, which increased electrical conductivity and decreased the Seebeck coefficient. The Cu<sup>+</sup> ions in the β-Cu<inf>2</inf>Se phase led to the reduced thermal conductivity. A low thermal conductivity of 0.86 W m<sup>−1</sup> K<sup>−1</sup> and a maximum dimensionless figure of merit of 0.32 at 523 K were realized for 10 min MHH sample. Finally, MHH showed very low energy consumption and saved time, which are essential for industrialization.
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    Improving the thermoelectric properties of thick Sb2Te3 film via Cu doping and annealing deposited by DC magnetron sputtering using a mosaic target
    (2021-11-01)
    Theekhasuk, Nattharika
    ;
    Sakdanuphab, Rachsak
    ;
    Nuthongkum, Pilaipon
    ;
    Pluengphon, Prayoonsak
    ;
    Harnwunggmoung, Adul
    Thick Cu-doped Sb<inf>2</inf>Te<inf>3</inf> films were deposited on flexible substrate by DC magnetron sputtering from a mosaic Cu–Sb<inf>2</inf>Te<inf>3</inf> target. The Cu-doped Sb<inf>2</inf>Te<inf>3</inf> films were vacuum annealed to improve their thermoelectric properties. Density functional theory was used to clarify the internal mechanism of the Cu doped into the Sb<inf>2</inf>Te<inf>3</inf> system. The results showed that Cu substitution on a Sb site induced electronic states or impurity peaks of Sb<inf>2</inf>Te<inf>3</inf> at a valence band maximum. The carrier concentration of the Cu-doped Sb<inf>2</inf>Te<inf>3</inf> films increased as the Cu-doped concentration increased. However, the crystallite size and Seebeck coefficient of the Cu-doped Sb<inf>2</inf>Te<inf>3</inf> films decreased as the Cu-doped concentration increased. Post-annealing treatment improved the microstructure and thermoelectric properties of the Cu-doped Sb<inf>2</inf>Te<inf>3</inf> films. The maximum electrical conductivity and power factor values of 754.20 S/cm at 50 °C and 1.56 10<sup>−3</sup> W/mK<sup>2</sup> at 100 °C were obtained in the annealed film with a Cu-doped concentration of 3 at%.
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    [Bi]:[Te] Control, Structural and Thermoelectric Properties of Flexible BixTey Thin Films Prepared by RF Magnetron Sputtering at Different Sputtering Pressures
    (2017-11-01)
    Nuthongkum, Pilaipon
    ;
    Sakdanuphab, Rachsak
    ;
    Horprathum, Mati
    ;
    Sakulkalavek, Aparporn
    In this work, flexible Bi<inf>x</inf>Te<inf>y</inf> thin films were prepared by radio frequency (RF) magnetron sputtering using a Bi<inf>2</inf>Te<inf>3</inf> target on polyimide substrate. The effects of sputtering pressures, which ranged between 0.6 Pa and 1.6 Pa on the [Bi]:[Te] ratio, and structural and thermoelectric properties were investigated. The [Bi]:[Te] ratio of thin film was determined by energy-dispersive spectrometry (EDS). The EDS spectra show the variation of the [Bi]:[Te] ratio as the sputtering pressure is varied. The film deposited at 1.4 Pa almost has a stoichiometric composition. The selective films with different [Bi]:[Te] ratios and sputtering pressures were characterized by their surface morphologies, crystal and chemical structures by field emission scanning electron microscopy (FE-SEM), x-ray diffraction (XRD) and Raman spectroscopy, respectively. Electrical transport properties, including carrier concentration and mobility, were measured by Hall effect measurements. Seebeck coefficients and electrical conductivities were simultaneously measured by a direct current four-terminal method (ZEM-3). The XRD and Raman spectroscopy results show a difference in microstructure between BiTe and Bi<inf>2</inf>Te<inf>3</inf> depending on the [Bi]:[Te] ratio. Electrical conductivity and Seebeck coefficient are related to the crystal and chemical structures. The maximum power factor of the Bi<inf>2</inf>Te<inf>3</inf> thin film is 9.5 × 10<sup>−4</sup> W/K<sup>2</sup> m at room temperature, and it increases to 12.0 × 10<sup>−4</sup> W/K<sup>2</sup> m at 195°C.
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    Investigation of Radiation Effect on Structural and Optical Properties of GaAs under High-Energy Electron Irradiation
    (2022-09-01)
    Phakkhawan, Authit
    ;
    Sakulkalavek, Aparporn
    ;
    Buranurak, Siritorn
    ;
    Klangtakai, Pawinee
    ;
    Pangza, Karnwalee
    A systematic investigation of the changes in structural and optical properties of a semi-insulating GaAs (001) wafer under high-energy electron irradiation is presented in this study. GaAs wafers were exposed to high-energy electron beams under different energies of 10, 15, and 20 MeV for absorbed doses ranging from 0–2.0 MGy. The study showed high-energy electron bombardments caused roughening on the surface of the irradiated GaAs samples. At the maximum delivered energy of 20 MeV electrons, the observed root mean square (RMS) roughness increased from 5.993 (0.0 MGy) to 14.944 nm (2.0 MGy). The increased RMS roughness with radiation doses was consistent with an increased hole size of incident electrons on the GaAs surface from 0.015 (0.5 MGy) to 0.066 nm (2.0 MGy) at 20 MeV electrons. Interestingly, roughness on the surface of irradiated GaAs samples affected an increase in material wettability. The study also observed the changes in bandgap energy of GaAs samples after irradiation with 10, 15, and 20 MeV electrons. The band gap energy was found in the 1.364 to 1.397 eV range, and the observed intense UV-VIS spectra were higher than in non-irradiated samples. The results revealed an increase of light absorption in irradiated GaAs samples to be higher than in original-based samples.