Theerayuth Plirdpring

Chalcopyrite CuGaTe2: A High‐Efficiency Bulk Thermoelectric Material

CuGaTe(2) with a chalcopyrite structure demonstrates promising thermoelectric properties. The maximum figure of merit ZT is 1.4 at 950 K. CuGaTe(2) and related chalcopyrites are a new class of high-efficiency bulk thermoelectric material for high-temperature applications.

High-temperature thermoelectric properties of Cu1–xInTe2 with a chalcopyrite structure

We investigated the high-temperature thermoelectric properties of Cu1–xInTe2 (x = 0, 0.05, 0.1, 0.2) at 310–710 K. The electrical properties of this system were optimized by the presence of substoichiometric amounts of copper and additional phonon scattering by lattice defects and a secondary phase reduced the thermal conductivity of the system. The samples of Cu1–xInTe2 (x = 0, 0.05, 0.1, 0.2) all had dimensionless figures of merit in excess of 0.5 at 710 K with a maximum value of 0.54 for x = 0.1.

Thermoelectric properties of Ga-added CoSb3 based skutterudites

Filled skutterudite compounds are known as excellent thermoelectric (TE) materials. It is known that the voids in the structure of the skutterudite compounds, such as CoSb3, can be filled or partially filled with a variety of different atoms, and, thus, obtained filled skutterudite compounds exhibit quite low thermal conductivity (κ). In the present study, we tried to fill Ga into the voids of CoSb3. The polycrystalline samples of GaxCo4Sb12 (x = 0.05, 0.10, 0.15, 0.20, 0.25, and 0.30) were prepared, and the TE properties were examined from room temperature to 750 K. All the samples were composed of two phases: GaxCo4Sb12 (x = ∼0.02) as the matrix phase and Ga metal as the second phase. All the samples exhibited negative values of the Seebeck coefficient (S). The Hall carrier concentration slightly increased with increasing x, while the carrier mobility decreased. Although the maximum Ga filling ratio was really low, the κ was reduced effectively by Ga adding. The maximum value of the dimensionless figure...

High-temperature thermoelectric properties of Cu2Ga4Te7 with defect zinc-blende structure

Here we show the high-temperature thermoelectric (TE) properties of Cu2Ga4Te7 with the defect zinc-blende structure in which one-seventh of the cation sites are structural vacancies. Cu2Ga4Te7 exhibited relatively low electrical resistivity (ρ) and thermal conductivity (κ) and moderate positive Seebeck coefficient (S) at high temperatures, making this compound a promising high-performance p-type TE material. At 940 K, the S, ρ, and κ were +215 μV K−1, 10.1×10−5 Ω m, and 0.67 Wm−1 K−1, respectively, which resulted in the maximum dimensionless figure of merit ZT (=S2T/ρ/κ, where T is the absolute temperature) of 0.64.

Enhancement of thermoelectric properties of CoSb3-based skutterudites by double filling of Tl and In

Thermoelectric (TE) generators can directly generate electrical power from waste heat, and thus could be an important part of the solution to future power supply and sustainable energy management. The main obstacle to the widespread use of TE materials in diverse industries, e.g., for exhaust heat recovery in automobiles, is their low efficiency in converting heat to electricity. The conversion efficiency of TE materials is quantified by the dimensionless figure of merit, ZT, and the way to enhance ZT is to decrease the lattice thermal conductivity (κlat) of the material, while maintaining a high electrical conductivity, i.e., to create a situation in which phonons are scattered but electrons are unaffected. Here, we report skutterudites filled by Tl and In, Tl0.1InxCo4Sb12, which allow a dramatic reduction of κlat, yielding a ZT of 1.2 at 700 K. We demonstrate that the reduction of κlat is due to the effective phonon scattering induced both by the rattling of Tl and In and by the naturally formed In2O3 n...

Effects of the Defects on the Thermoelectric Properties of Cu-In-Te Chalcopyrite-Related Compounds

We prepared and investigated the thermoelectric properties of Cu0.4InTe2 at 310–710 K. The crystal structure of Cu0.4InTe2 was identical to that of CuIn3Te5, namely a tetragonal structure, space group P2c, known as an ordered defect chalcopyrite. This structure is different from that of CuInTe2, which has a normal chalcopyrite structure. In comparison with CuInTe2, Cu0.4InTe2 showed inferior thermoelectric properties because a degradation in its electrical conductivity outweighed a reduction in its thermal conductivity. The maximum dimensionless figure of merit of Cu0.4InTe2 was 0.17 at 702 K.

Effect of Annealing Temperature on Structure and Optical Properties of Ta2O5 Thin Films Prepared by DC Magnetron Sputtering

Tantalum oxide (Ta2O5) films at 400 nm thickness were prepared at room temperature by DC reactive magnetron sputtering. The effect of annealing temperature on film crystallinity, microstructure and optical properties were investigated. In order to indentify the crystalline structure and film morphology, X-ray diffraction (XRD) and field-emission scanning electron microscope (FE-SEM) measurements were performance. The optical properties were determined by UV-Vis spectrophotometer and spectroscopic ellipsometry (SE). The result showed that, with the annealing treatment at high temperature (700-900°C), the as-deposited films were crystallized to orthorhombic phase of tantalum pentaoxide (β-Ta2O5). In addition, the transmittance spectrum percentage indicated 87%, which corresponded to the obtained optical characteristic. The refractive index varied at 550 nm from 2.17 to 2.21 with increased of the annealing temperature.

Growth of Nanostructure TiO2 Films by Glancing Angle Deposition

Nanostructure TiO2 films were prepared by electron beam evaporation with glancing angle deposition technique at room temperature. The morphology, crystal structure and optical properties at various substrate rotation speeds (0-10 rpm) were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and UV-vis spectrophotometer. The cross-section FE-SEM images illustrate that the nanostructures consist of different morphology: slanted columnar, spiral and vertical align nanorods at 0, 0.01 and 10 rpm-rotation speed, respectively. In particular, the rotation speed-controlled incoming vapor flux was found to play crucial role in the growth of nanostructure TiO2 films.