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Corresponding author: email psupree@kk.ac.th, Phone: þ66 87 373 11 22, Fax: þ66 43 203 359 In this research, the p-type Si 80 Ge 20 B 3 alloys composited with YSi 2 nanoinclusions were fabricated by melting spinning and then, spark plasma sintering. The metallic Y was chosen as the source of YSi 2 nanoparticles. It was found that the fully dense nanocomposites were formed with the homogeneous distribution of YSi 2 nanoinclusions in the SiGe matrix. The thermoelectric measurement showed that YSi 2 addition reduces the electrical conductivity but increases the Seebeck coefficient, which was attributed to the decrease in carrier concentration. The thermal conductivity was suppressed for the composite SiGe-1.4%Y, which made this composition to exhibit the largest thermoelectric figure-of-merit (ZT) of 0.52. Figure-of-merit (ZT) and microstructure of the SiGe-x%Y SiGe-1.4%Y.

Hydrogen adsorption energies of Be-, Zn-, and Cd-zeolitic imidazolate framework-23 were investigated using the Van der Waals density functional theory implemented in the Quantum ESPRESSO program. From the structural parameters of these systems, we found that the imidazole ligand is unchanged and only the tetrahedral metal nitride cluster is varied. Moreover, our results revealed that the Cd-zeolitic imidazolate framework-23 has the highest electric dipole moment followed by Zn-and Be-zeolitic imidazolate framework-23. On the basis of hydrogen adsorption energy calculations, we found that hydrogen molecules cannot bind with either Be-or Zn-zeolitic imidazolate framework-23 at any of the considered adsorption sites, whereas hydrogen molecules can be trapped on the Cd-zeolitic imidazolate framework-23 with the hydrogen binding energy in the range from 60 to 130 meV. This result suggested that replacing Zn in the metal nitride cluster with a larger metal can enhance the hydrogen adsorption energy of zeolitic imidazolate framework-23.

Yttrium silicide (YSi 2 ) nanoparticles in SiGe are reported to enhance the thermoelectric figure-of-merit (ZT) to the recorded value (%1.81). However, the thermoelectric properties of bulk YSi 2 has never been reported. In this work, the thermoelectric properties of YSi 2 is studied for the first time. The bulk YSi 2 is fabricated by arc melting highly pure Si and Y raw materials. The ingot is crushed to powder and compacted to form a highly dense pellet by spark plasma sintering. By optimizing the processing parameters, the single phase with the AlB 2 -type structure (P6/mmm) is formed. The Hall measurements show that YSi 2 exhibit a metallic-like behavior with a very high electron concentration. This result in the thermoelectric properties with a very large electrical conductivity (%18 Â 10 5 Ω À1 m À1 ) but a small Seebeck coefficient (À26 mV K À1 ) at room temperature, and decrease with temperature. The thermal conductivity is around 14-19 W m À1 K À1 for all temperature range. The maximum ZT value is 0.026 at 423 K.

Mo3Sb7 has been known as a p-type metal with commonly poor thermoelectric properties. However, Mo3Sb7 can be a high-efficiency thermoelectric material, owing to its capability of a metal–semiconductor transition, which can be realized by adding two valence electrons through elemental substitutions. Among the Mo3Sb7-based compounds, Mo3Sb5.4Te1.6 shows the highest figure of merit, zT, but additional valence electrons are needed for further improvement of the figure of merit. Here, we try to enhance the figure of merit of Mo3Sb7 by iodine-doping and by synthesizing and characterizing Mo3Sb7Ix with x = 0, 0.50, 0.75, 1.00, 1.25, and 1.50, where antimony (valence electrons = 5) is replaced by iodine (valence electrons = 7). We confirmed that the solubility limit for iodine in Mo3Sb7Ix was 1.25 < x < 1.50, and the figure of merit was enhanced by approximately 65% in maximum in x = 1.25.