Abstract
Cu–Sb–Se ternary chalcogenide compounds composed of earth-abundant low-toxicity elements are attracting attention as economical and ecofriendly semiconductors. Among them, permingeatite (Cu₃SbSe₄) is a potential thermoelectric material with high Seebeck coefficient and low lattice thermal conductivity. However, it is necessary to improve its thermoelectric properties through doping, as it has low..... More

Abstract
Bytizite (Cu₃SbSe₃ ) has attracted interest as a promising thermoelectric material because of its ultralow thermal conductivity; however, there are few experimental studies. This study investigated the optimal processing conditions for the synthesis of Cu₃SbSe₃ using mechanical alloying (MA) and hot pressing (HP). The MA powder exhibited an orthorhombic Cu₃SbSe₃..... More

Abstract
Famatinite (Cu₃SbS₄ ) is a promising p-type thermoelectric material because of its low lattice thermal conductivity and high Seebeck coefficient. In this study, famatinite powders, double-doped with Sn (a B^IV group element) and In (a B^III group element) to give Cu₃Sb_1-x-ySn_xIn_yS₄ (0.02 ≤ x ≤ 0.12 and 0.06 ≤..... More

Abstract
Skinnerite (Cu₃SbS₃) has recently attracted attention as a promising thermoelectric material because of its low thermal conductivity. In this study, we performed the solid-state synthesis of Fe-doped skinnerite Cu₃Sb_1-yFe_yS₃ (y = 0.02−0.06) using mechanical alloying and hot pressing, and examined the samples’ thermoelectric properties relative to Fe doping content. All..... More

Abstract
Permingeatite (Cu₃SbSe₄) is a promising thermoelectric material with narrow bandgap energy and large carrier effective mass. However, doping is required to improve its electrical conductivity and thermoelectric properties. In this study, Cu₃Sb_1−y(Al/In)_ySe₄ doped with B^III-group elements (Al or In) at the Sb sites was synthesized using mechanical alloying followed by..... More

Abstract
In this study, mechanical alloying was performed to synthesize permingeatite Cu₃Sb_1-x-ySn_xBi_ySe₄ (0.02 ≤ x ≤ 0.06 and 0.02 ≤ y ≤ 0.04) doped with Sn and Bi. Hot pressing was subsequently conducted to achieve dense sintered bodies. When the Bi content was constant, the carrier concentration increased with the Sn..... More

Abstract
Skinnerite Cu₃SbS₃, which consists of non-toxic and low-cost elements, is a potential thermoelectric material, however, studies on its thermoelectric properties are limited. In this study, the optimal conditions of mechanical alloying (MA) and hot pressing (HP) for the synthesis of the Cu₃SbS₃ phase were investigated, and its thermoelectric properties were..... More

Abstract
Si-doped Cu₁₂Sb_4-ySi_yS₁₃ (y = 0.1-0.4) compounds were prepared using solid-state synthesis. Each specimen consisted of a single tetrahedrite phase with a densely sintered body whose relative density exceeded 98.9%. The lattice constant decreased from 1.0357 nm to 1.0336 nm as the Si content increased. When the Si doping content (y)..... More

Abstract
Ge-doped tetrahedrites Cu₁₂Sb_4-yGe_yS₁₃ (y = 0.1–0.4) were prepared using mechanical alloying and hot pressing. An X-ray diffraction analysis after mechanical alloying showed a single tetrahedrite phase without secondary phases. The tetrahedrite phase was stable after hot pressing at 723 K under 70 MPa. As the Ge content increased, the lattice..... More

Abstract
In this study, tetrahedrite compounds doped with Sn were prepared by mechanical alloying and hot pressing, and their charge transport and thermoelectric properties were analyzed. X-ray diffraction analysis revealed that both the synthetic powders and sintered bodies were synthesized as a single tetrahedrite phase without secondary phases. Densely sintered specimens..... More

Abstract
Tetrahedrite is a promising thermoelectric material mainly due to its low thermal conductivity, a consequence of its complicated crystal structure. However, tetrahedrite has a high hole concentration; therefore, optimizing carrier concentration through doping is required to maximize the power factor. In this study, Te-doped tetrahedrites Cu₁₂Sb_4-yTe_yS₁₃ (0.1 ≤ y ≤..... More

Abstract
Permingeatites Cu₃Sb_1−yGe_ySe₄ (0 ≤ y ≤ 0.14) were synthesized by mechanical alloying and hot pressing. The charge-transport parameters (Hall coefficient, carrier concentration, mobility, and Lorenz number) and thermoelectric properties (electrical conductivity, Seebeck coefficient, power factor, thermal conductivity, and figure of merit) were examined with respect to the Ge doping level...... More

Abstract
Mn-doped tetrahedrites Cu_12-xMn_xSb₄S₁₃ (0.1 ≤ x ≤ 0.4) were synthesized by mechanical alloying (MA) and sintered by hot pressing (HP). A single tetrahedrite phase was synthesized by MA without post-annealing, and it was stable without any phase changes after HP. The hot-pressed specimens had a relative density higher than 98.6%...... More

Abstract
Tetrahedrite (C₁₂Sb₄S₁₃) has attracted attention as a p-type thermoeletric material with very low thermal conductivity induced by the anharmonic oscillation of Cu due to the lone-pair electrons of Sb. Many studies have been conducted to improve its thermoelectric performance by partially substituting the transition elements for the Cu sites. In..... More

Abstract
Tetrahedrite has low lattice thermal conductivity because of the lone-pair electrons of Sb, which cause the Cu atoms to vibrate at a low frequency and high amplitude. The synthesis of tetrahedrite compounds by conventional melting methods requires a long-time reaction and annealing. However, a homogeneous and solid-state synthesis can be..... More

Abstract
Tetrahedrite Cu12Sb4S13 has low lattice thermal conductivity because of the lone-pair electrons of Sb, which cause the Cu atoms to vibrate at a low frequency and high amplitude. When the Cu atoms of Cu12Sb4S13 are partially substituted with a transition metal, changes in the Cu vibrations can intensify phonon scattering,..... More

Abstract
Higher manganese silicides (HMSs) MnSi1.74-1.75:Gem (m = 0.01–0.04) were prepared by solid-state reaction and hot pressing. The major phases of the HMSs were Mn27Si47 or Mn4Si7, and a small quantity of Si remained, but the intermetallic compound MnSi was not formed. The lattice constant increased with the substitution of Ge..... More

Abstract
Ge-doped higher manganese silicides (HMSs) MnSi_1.72–1.73:Ge_m (m = 0.01-0.04) were prepared and their thermoelectric properties were studied. HMS powders were synthesized by solid-state reaction of raw material powders (Mn, Si, and Ge) at 1273 K for 6 h in vacuum, and hot-pressed at 1173 K for 2 h under 70..... More

Abstract
Iodine-doped n-type Bi_2-xSb_xTe_3-ySe_y:I_m (x = 0.1–0.2, y = 0.15–0.6, and m = 0.0025–0.005) quaternary solid solutions were prepared by encapsulated melting (EM) and hot pressing (HP). The lattice constants of the resulting materials decreased with increasing Sb and Se contents, whereas the amount of I dopant was too small to..... More

Abstract
Cu₂Se exhibits very low thermal conductivity and the origin is known to be the "liquid-like" behavior of Cu ions around the sub-lattice of Se. Due to its very high ZT, research interest in the thermoelectric properties of this material has been increasing rapidly. However, most studies have used a conventional melting..... More

Abstract
We report the effects of interface control using reduced graphene oxide (RGO) on the thermoelectric transport properties of polycrystalline SnSe compounds. Polycrystalline SnSe-RGO composites were prepared by the consolidation of SnSe powder coated with the RGO by hot pressing, and the RGO content was controlled to be 0, 0.2, 0.5..... More

Abstract
Bi_2-xSb_xTe₃ (x = 1.4–1.7) solid solutions were synthesized by mechanical alloying (MA) and consolidated by hot pressing (HP), and their charge transport and thermoelectric properties were examined. The relative densities of the hot-pressed specimens were higher than 96% on average. As the Sb content was increased, the lattice constants decreased,..... More

Abstract
We report the effects of Sb content on the charge transport and power factor of Bi_2-xSb_xTe₃(1.56 ≤χ≤ 1.74) compounds prepared by hot pressing. From the temperature-dependence of the electrical conductivity, it was found that the charge transport in the compounds was predominantly governed by acoustic phonon scattering, and additionally affected..... More

Abstract
We report the effects of incorporated Cu on the thermoelectric transport properties of Bi_0.42Sb_1.58Te₃ compounds prepared by the hot pressing method. The hole concentration in the compound increased significantly with the increase in the Cu content. The acceptor role of Cu was manifested by Hall measurements and also by the..... More