Publications by authors named "Jong-Soo Rhyee"

Article Synopsis
  • GeTe-based alloys are being explored as nontoxic alternatives to traditional thermoelectric materials like PbTe, with recent studies showing I-doping enhances their performance through increased lattice anharmonicity and lower phase transition temperatures.
  • Sb doping in GeTeI contributes to better thermoelectric performance by softening the lattice and promoting band convergence, which leads to reduced lattice thermal conductivity and higher valley degeneracy.
  • The findings indicate that as Sb concentration increases, changes in the electronic band structure, such as a decrease in carrier mobility and an optimized carrier concentration, result in significant performance improvements, especially noted with a peak value of 1.70 for GeSbTeI at 723 K.
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We investigated the magnetocaloric and electrical transport properties of the EuCuNiSi clathrate compound, synthesized by an arc melting and annealing method. X-ray photoemission spectroscopy revealed a mixed valence state of Eu and Eu. The low-field and low-temperature magnetic measurements indicated a multiple magnetic transition, from ferromagnetic near 35 K to antiferromagnetic at 25 K.

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This study reports the synthesis of type-I BaCuNiGaSi clathrate as a single crystal by the flux method and physical properties investigations such as structural, chemical, magnetic, and thermal properties. Structural refinements indicate Ba atoms are situated at 2a and 6d positions with mixed occupancy across framework sites. Raman spectroscopy assessed host-guest interactions, while the compound's morphology and composition were investigated by the scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) analyses.

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We study the thermoelectric properties of a p-type BiSbTe (BST) composite with Ag nanoparticle-decorated TiO microparticles (US-Ag/TiO). The dispersion of US-Ag/TiO particles, synthesized by an ultrasonication (US) method, into the matrix effectively decreases lattice and bipolar thermal conductivity, attributed to the scattering centers formed at nano and micro scales. The electron backscattering diffraction (EBSD) measurements revealed smaller grain sizes within the BST composite when paired with the US-Ag/TiO particle dispersion.

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Article Synopsis
  • Magnetic anisotropy has a strong impact on how well materials exhibit the magnetocaloric effect, which can be significant in cooling applications.
  • The study focused on NdAlGe single crystal, revealing notable anisotropic magnetization properties, including a stable antiferromagnetic transition at 6 K and a metamagnetic spin reorientation at lower temperatures.
  • The magnetocaloric effect was substantial, with a large negative entropy change of -13.80 J/kg K at 5.5 K under a magnetic field, as well as an inverse effect observed at 6 K, indicating NdAlGe's potential in developing innovative magnetocaloric refrigeration systems.
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High-entropy alloy (HEA) superconductors-a new class of functional materials-can be utilized stably under extreme conditions, such as in space environments, owing to their high mechanical hardness and excellent irradiation tolerance. However, the feasibility of practical applications of HEA superconductors has not yet been demonstrated because the critical current density (J) for HEA superconductors has not yet been adequately characterized. Here, we report the fabrication of high-quality superconducting (SC) thin films of Ta-Nb-Hf-Zr-Ti HEAs via a pulsed laser deposition.

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Carbon quantum dots (CQDs) are promising carbonaceous nanomaterials fortuitously discovered in 2004. CQDs are the rising stars in the nanotechnology ensemble because of their unique properties and widespread applications in sensing, imaging, medicine, catalysis, and optoelectronics. CQDs are notable for their excellent solubility and effective luminescence and, as a result, they are also known as carbon nanolights.

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The present study develops a general framework for weak antilocalization (WAL) in a three-dimensional (3D) system, which can be applied for a consistent description of longitudinal resistivity [Formula: see text] and Hall resistivity [Formula: see text] over a wide temperature (T) range. Compared to the previous approach Vu et al. (Phys Rev B 100:125162, 2019), which assumes infinite phase coherence length (l) and a zero spin-orbit scattering length (l), the present framework is more general, covering high T and the intermediate spin-orbit coupling strength.

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Developing inexpensive and rapid fabrication methods for high efficiency thermoelectric alloys is a crucial challenge for the thermoelectric industry, especially for energy conversion applications. Here, we fabricated large amounts of p-type CuBiSbTe alloys, using water atomization to control its microstructure and improve thermoelectric performance by optimizing its initial powder size. All the water atomized powders were sieved with different aperture sizes, of 32-75 μm, 75-125 μm, 125-200 μm, and <200 μm, and subsequently consolidated using hot pressing at 490 °C.

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Bismuth-Telluride-based compounds are unique materials for thermoelectric cooling applications. Because BiTe is a narrow gap semiconductor, the bipolar diffusion effect is a critical issue to enhance thermoelectric performance. Here, we report the significant reduction of thermal conductivity by decreasing lattice and bipolar thermal conductivity in extrinsic phase mixing of MgO and VO nanoparticles in BiSbTe (BST) bulk matrix.

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  • The study explored thermoelectric properties of PbSnSe and PbSnSeCl compounds, focusing on how chlorine doping affects performance.
  • Low levels of Cl doping (below 0.3 mol.%) increased carrier concentration and mobility, leading to better electrical transport due to enhanced mean free path.
  • Additionally, the combination of chlorine doping and Pb excess improved thermoelectric performance by reducing lattice thermal conductivity and amplifying carrier effective mass, which is advantageous for achieving high thermoelectric efficiency.
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We investigated the anisotropic thermoelectric properties of the BiTeSeI (x = 0.0, 0.1, 0.

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One promising approach to improving thermoelectric energy conversion is to use nanostructured interfaces that enhance Seebeck coefficient while reducing thermal conductivity. Here, we synthesized Au-CuSe core-shell nanoparticles with different shell thicknesses by controlling the precursor concentration in solution. The Au-CuSe core-shell nanoparticles are about 37-53 nm in size, and the cores of the nanostructures are composed of Au nanoparticles with sizes of ∼11 nm.

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  • Researchers explored the thermoelectric properties of CuI-doped BiTeSe compounds, focusing on how the codoping affects the materials' lattice structure and transport properties.
  • They observed first-order phase transitions at specific temperatures, confirming these transitions are not structural, and noted behavior indicative of charge density wave transitions affecting electrical and thermal conductivities.
  • The findings revealed that the charge density wave formation in these compounds improves thermoelectric performance, achieving a ZT value of over 1.0 at high temperatures, surpassing previous records.
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  • The study examines various magnetic properties of the Kitaev honeycomb iridate Cu2IrO3, revealing that even with chemical disorders, there are no signs of spin glass behavior down to 260 mK.
  • Despite the lack of static magnetism, the results indicate dynamic spin behavior, as shown by muon spin relaxation measurements.
  • Scaling relations in magnetic susceptibility and magnetization suggest the influence of bond randomness, but specific heat measurements point to unexpected low-lying excitations, highlighting the complex effects of quenched disorder in this spin system.
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Considerable efforts have been devoted to enhancing thermoelectric performance, by employing phonon scattering from nanostructural architecture, and material design using phonon-glass and electron-crystal concepts. The nanostructural approach helps to lower thermal conductivity but has limited effect on the power factor. Here, we demonstrate selective charge Anderson localization as a route to maximize the Seebeck coefficient while simultaneously preserving high electrical conductivity and lowering the lattice thermal conductivity.

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Article Synopsis
  • BiTe-based compounds are promising for room-temperature cooling and waste heat recovery, with quaternary mixtures like BiTe-BiSe-BiS showing potential for mid-temperature power generation under 500 °C.
  • The study discovered that lattice disorder in these compounds, resulted from multiple element substitutions, impacts electrical resistivity and carrier behavior, shifting from p-type to n-type at intermediate temperatures.
  • By co-doping with CuI, electrical resistivity decreased, carrier delocalization improved thermoelectric performance, achieving a high value of 0.85 at 523 K, which is advantageous for n-type materials in that temperature range.
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Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator PbSnTe.

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Topological insulators generally share commonalities with good thermoelectric (TE) materials because of their narrow band gaps and heavy constituent elements. Here, we propose that a topological crystalline insulator (TCI) could exhibit a high TE performance by breaking its crystalline symmetry and tuning the chemical potential by elemental doping. As a candidate material, we investigate the TE properties of the Cl-doped TCI PbSnSe.

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Thin-film transistors (TFTs) based on multilayer molybdenum diselenide (MoSe ) synthesized by modified atmospheric pressure chemical vapor deposition (APCVD) exhibit outstanding photoresponsivity (103.1 A W ), while it is generally believed that optical response of multilayer transition metal dichalcogenides (TMDs) is significantly limited due to their indirect bandgap and inefficient photoexcitation process. Here, the fundamental origin of such a high photoresponsivity in the synthesized multilayer MoSe TFTs is sought.

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The data presented in this article are related to the research article entitled "High thermoelectric performance in pseudo quaternary compounds of (PbTe) (PbSe)(PbS) by simultaneous band convergence and nano precipitation" (Ginting et al., 2017) [1]. We measured electrical and thermal transport properties such as temperature-dependent Hall carrier density , Hall mobility , thermal diffusivity , heat capacity , and power factor in (PbTe) (PbSe)(PbS) (=0.

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Large-area and highly crystalline CVD-grown multilayer MoSe2 films exhibit a well-defined crystal structure (2H phase) and large grains reaching several hundred micrometers. Multilayer MoSe2 transistors exhibit high mobility up to 121 cm(2) V(-1) s(-1) and excellent mechanical stability. These results suggest that high mobility materials will be indispensable for various future applications such as high-resolution displays and human-centric soft electronics.

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Researchers have long been searching for the materials to enhance thermoelectric performance in terms of nano scale approach in order to realize phonon-glass-electron-crystal and quantum confinement effects. Peierls distortion can be a pathway to enhance thermoelectric figure-of-merit by employing natural nano-wire-like electronic and thermal transport. The phonon-softening known as Kohn anomaly, and Peierls lattice distortion decrease phonon energy and increase phonon scattering, respectively, and, as a result, they lower thermal conductivity.

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We investigated the thermoelectric properties of Cl-doped polycrystalline compounds In4Pb0.01Sn0.03Se2.

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