Half-Heusler alloys are a potential thermoelectric material for use in high-temperature applications. In an attempt to produce half-Heusler thermoelectric materials with fine microstructures, TiCoSb was synthesized by the mechanical alloying of stoichiometric elemental powder compositions and then consolidated by vacuum hot pressing. The phase transformations during the mechanical alloying and hot consolidation process were investigated using XRD and SEM. A single-phase, half- Heusler allow was successfully produced by the mechanical alloying process, but a minor portion of the second phase of the CoSb formation was observed after the vacuum hot pressing. The thermoelectric properties as a function of the temperature were evaluated for the hot-pressed specimens. The Seebeck coefficients in the test range showed negative values, representing n-type conductivity, and the absolute value was found to be relatively low due to the existence of the second phase. It is shown that the electrical conductivity is relatively high and that the thermal conductivities are compatibly low in MA TiCoSb. The maximum ZT value was found to be relatively low in the test temperature range, possibly due to the lower Seebeck coefficient. The Hall mobility value appeared to be quite low, leading to the lower value of Seebeck coefficient. Thus, it is likely that the single phase produced by mechanical alloying process will show much higher ZT values after an excess Ti addition. It is also believed that further property enhancement can be obtained if appropriate dopants are selectively introduced into this MA TiCoSb System.

Half-heusler phase ZrNiSn is one of the potential thermoelectric materials for high temperature application. In an attempt to investigate the effect of Sb doping on thermoelectric properties, half-heusler phase () was synthesized by mechanical alloying of stoichiometric elemental powder compositions, and consolidated by vacuum hot pressing. Phase transformations during mechanical alloying and hot consolidation were investigated using XRD. Sb doped ZrNiSn was successfully produced in all doping ranges by vacuum hot pressing using as-milled powders without subsequent annealing. Thermoelectric properties as functions of temperature and Sb contents were evaluated for the hot pressed specimens. Sb doping up to x=0.04 in was shown to be effective on thermoelectric properties and the figure of merit (ZT) was shown to reach to the maximum at x=0.02 in this study.

In this study, p-type : TAGS-85 compound powders were prepared by gas atomization process, and then their microstructures and mechanical properties were investigated. The fabricated powders were of spherical shape, had clean surface, and illustrated fine microstructure and homogeneous + GeTe solid solution. Powder X-ray diffraction results revealed that the crystal structure of the TAGS-85 sample was single rhombohedral GeTe phase, which with a space group . The grain size of the powder particles increased while the micro Vickers hardness decreased with increasing annealing temperature within the range of 573 K and 723 K due to grain growth and loss of Te. In addition, the crystal structure of the powder went through a phase transformation from rhombohedral () at low-temperature to cubic () at high-temperature with increasing annealing temperature. The micro Vickers hardness of the as-atomized powder was around 165 Hv, while it decreased gradually to 130 Hv after annealing at 673K, which is still higher than most other fabrication processes.

The present study focused on the synthesis of Bi-Te-Se-based powder by an oxide-reduction process, and analysis of the thermoelectric properties of the synthesized powder. The phase structure, chemical composition, and morphology of the synthesized powder were analyzed by XRD, EPMA and SEM. The synthesized powder was sintered by spark plasma sintering. The thermoelectric properties of the sintered body were evaluated by measuring its Seebeck coefficient, electrical resistivity, and thermal conductivity. powder was synthesized from a mixture of , , and powders by mechanical milling, calcination, and reduction. The sintered body of the synthesized powder exhibited n-type thermoelectric characteristics. The thermoelectric properties of the sintered bodies depend on the reduction temperature. The Seebeck coefficient and electrical resistivity of the sintered body were increased with increasing reduction temperature. The sintered body of the powder synthesized at showed about 0.5 of the figure of merit (ZT) at room temperature.

Thermoelectric-thick films were fabricated by using a screen printing process of n and p-type bismuth-telluride-based pastes. The screen-printed thick films have approximately 30 in thickness and show rough surfaces yielding an empty gap between an electrode and the thick film. The gap might result in an increase of an electrical resistivity of the fabricated thick-film-type thermoelectric module. In this study, we suggest a conductive metal coating onto the surfaces of the screen-printed paste in order to reduce the contact resistance in the module. As a result, the electrical resistivity of the thermoelectric module having a gold coating layer was significantly reduced up to 30% compared to that of a module without any metal coating. This result indicates that an introduction of conductive metal layers is effective to decrease the contact resistivity of a thick-film-typed thermoelectric module processed by screen printing.

Microelectromechanical systems (MEMS)-fabricated suspended devices were used to measure the in-plane electrical conductivity, Seebeck coefficient, and thermal conductivity of 304 nm and 516 nm thick InGaAlAs films with 0.3% ErAs nanoparticle inclusions by volume. The suspended device allows comprehensive thermoelectric property measurements from a single thin film or nanowire sample. Both thin film samples have identical material compositions and the sole difference is in the sample thickness. The measured Seebeck coefficient, electrical conductivity, and thermal conductivity were all larger in magnitude for the thicker sample. While the relative change in values was dependent on the temperature, the thermal conductivity demonstrated the largest decrease for the thinner sample in the measurement temperature range of 325 K to 425 K. This could be a result of the increased phonon scattering due to the surface defects and included ErAs nanoparticles. Similar to the results from other material systems, the combination of the measured data resulted in higher values of the thermoelectric figure of merit (ZT) for the thinner sample; this result supports the theory that the reduced dimensionality, such as in twodimensional thin films or one-dimensional nanowires, can enhance the thermoelectric figure of merit compared with bulk threedimensional materials. The results strengthen and provide a possible direction in locating and optimizing thermoelectric materials for energy applications.

The electro-deposition of compound semiconductors has been attracting more attention because of its ability torapidly deposit nanostructured materials and thin films with controlled morphology, dimensions, and crystallinity in a cost-effective manner (1). In particular, low band-gap A2B3-type chalcogenides, such as Sb2Te3 and Bi2Te3, have been extensivelystudied because of their potential applications in thermoelectric power generator and cooler and phase change memory.Thermoelectric SbxTey films were potentiostatically electrodeposited in aqueous nitric acid electrolyte solutions containingdifferent ratios of TeO2 to Sb2O3. The stoichiometric SbxTey films were obtained at an applied voltage of −0.15V vs. SCE usinga solution consisting of 2.4mM TeO2, 0.8mM Sb2O3, 33mM tartaric acid, and 1M HNO3. The stoichiometric SbxTey filmshad the rhombohedral structure with a preferred orientation along the [015] direction. The films featured hole concentrationand mobility of 5.8×1018/cm3 and 54.8cm2/V·s, respectively. More negative applied potential yielded more Sb content in thedeposited SbxTey films. In addition, the hole concentration and mobility decreased with more negative deposition potential andfinally showed insulating property, possibly due to more defect formation. The Seebeck coefficient of as-deposited Sb2Te3 thinfilm deposited at −0.15V vs. SCE at room temperature was approximately 118µV/K at room temperature, which is similarto bulk counterparts.

The p-type thermoelectric compounds of based doped with 3wt% Te were fabricated by a combination of rapid solidification and spark plasma sintering (SPS) process. The effect of holding time during spark plasma sintering (SPS) on the microstructure and thermoelectric properties were investigated using scanning electron microscope (SEM), X-ray diffraction (XRD) and thermoelectric properties. The powders as solidified consisted of homogeneous thermoelectric phases. The thermoelectric figure of merit measured to be maximum () at the SPS temperature of .

In this study, as high temperature performance capable thermoelectric materials was manufactured by powder metallurgy.The as-casted Fe-Si alloy was annealed for homogenization below for 3 h. Due to its high brittleness, the cast alloy transformed to fine powders by ball-milling, followed by subsequent compaction (hydraulic pressure; 2 GPa) and sintering (, 12 h). In order to precipitate , heat treatment was performed at with varying dwell time (7, 15 and 55 h). As a result of this experiment thermoelectric phase was quickly transformed by powder metallurgical process. There was not much change in powder factor between 7h and 55h specimens.

The present study focused on the synthesis of Bi-Sb-Te-based thermoelectric powder by an oxidereduction process. The phase structure, particle size of the synthesized powders were analyzed using XRD and SEM. The synthesized powder was sintered by the spark plasma sintering method. The thermoelectric property of the sintered body was evaluated by measuring the Seebeck coefficient and specific electric resistivity. The powder had been synthesized by a combination of mechanical milling, calcination and reduction processes using mixture of , and powders. The sintered body of the powder synthesized by an oxide-reduction process showed p-type thermoelectric characteristics, even though it had lower thermoelectric properties than the sintered body of the thermoelectric powder synthesized by the conventional melting-crushing method.

Bismuth-telluride based thermoelectric powders were fabricated by two-step planetary milling process which produces bimodal size distribution ranging . The powders were reduced in hydrogen atmosphere to minimize oxygen contents which cause degradation of thermoelectric performance by decreasing electrical conductivity. Oxygen contents were decreased from 0.48% to 0.25% by the reduction process. In this study, both the as-synthesized and the reduced powders were consolidated by the spark plasma sintering process at for 10 min at the heating rate of and then their thermoelectric properties were investigated. The sintered samples using the reduced p-type thermoelectric powders show 15% lower specific electrical resistivity () than those of the as-synthesized powders while Seebeck coefficient and thermal conductivity do not change a lot. The results confirmed that ZT value of thermoelectric performance at room temperature was improved by 15% due to high electric conductivity caused by the controlled oxygen contents present at bismuth telluride materials.

Carbon-nanotube-embedded bismuth telluride (CNT/) matrix composites were fabricated by a powder metallurgy process. Composite powders, whereby 5 vol.% of functionalized CNTs were homogeneously mixed with alloying powders, were successfully synthesized by using high-energy ball milling process. The powders were consolidated into bulk CNT/ composites by spark plasma sintering process at for 10 min. The fabricated composites showed the uniform mixing and homogeneous dispersion of CNTs in the matrix. Seebeck coefficient of CNT/ composites reveals that the composite has n-type semiconducting characteristics with values ranging to with increasing temperature. Furthermore, the significant reduction in thermal conductivity has been clearly observed in the composites. The results showed that CNT addition to thermoelectric materials could be useful method to obtain high thermoelectric performance.

Recently, it was under an obligation to install the VOCs recycling unit in the cleaners and the gas station to prevent from discharging VOCs emitted from the cleaners and the gas station. The objectives of this study was to investigate the VOCs recycling unit used thermoelectric module to recycle the organic solvent from the cleaners and after washing. The traditional way was the use of the VOCs recycling unit with the compressor. But the recycling unit has many weak points , noise, size, danger of fire, additional pollution and so on. In order to improve these weak points, it was developed the new VOCs recycling unit using the thermoelectric module through this study. The cooling block with 32 thermoelectric module was applied to cool the hot VOCs where comes to occur from the dryer in high temperature condition. Also a water-cooled equipment was used to remove the heat from the hot surface of thermoelectric module. The experimental results from new VOCs recycling unit shows that the maximum recovery rate of the unit was 83.2 % and the recycled VOCs' purity was 98 % or more. And the noise problem was solved by applying the thermoelectic module to the VOCs recycling unit.

The present study focused on the synthesis of a bismuth-antimony-tellurium-based thermoelectric nanopowders using plasma arc discharge process. The chemical composition, phase structure, particle size of the synthesized powders under various synthesis conditions were analyzed using XRF, XRD and SEM. The powders as synthesized were sintered by the plasma activated sintering. The thermoelectric properties of sintered body were analyzed by measuring Seebeck coefficient, specific electric resistivity and thermal conductivity. The chemical composition of the synthesized Bi-Sb-Te-based powders approached that of the raw material with an increasing DC current of the are plasma. The synthesized Bi-Sb-Te-based powder consist of a mixed phase structure of the , and phases. This powder has homogeneous mixing state of two different particles in an average particle size; about 100nm and about 500nm. The figure of merit of the sintered body of the synthesized 18.75 wt.%Bi-24.68 wt.%Sb-56.57 wt.%Te nanopowder showed higher value than one of the sintered body of the mechanically milled 12.64 wt.%Bi-29.47 wt.%Sb-57.89 wt.%Te powder.

The effects of the dopant (Mn) ratio on the microstructure and thermoelectric properties of alloy were studied in this research. The alloy was fabricated by a combination process of ball milling and high pressure pressing. Structural behavior of the sintered bulks were systematically investigated by XRD, SEM, and optical microscopy. With increasing dopan (Mn) ratio, the density and phase of the sintered bulks increased and maximum density of 94% was obtained in the 0.07% Mn-doped alloy. The sintered bulks showed fine microstructure of , and phase. The semiconducting phase of was transformed from phase by annealing

In this study, the thermoelectric power and resistivity of the perovskite manganiteLa0.75Ba0.25MnO3 were investigated in the temperature range 300K-1200K. The electrical resistivity andthermoelectric power indicate a transport mechanism dominated by adiabatic small-polaron hopping. Thepower factor increases from 2×10−6W/mK2 to 1×10−5W/mK2 as to the temperature increases from 400K to1200K, which indicates that the compound is highly feasible as a thermoelectric material at high temperatures.

P-type thermoelectric material was sintered by Hot Press process (HP) and the effect of boron ( at%) addition on the thermoelectric properties were reported. To enhance the thermoelectric performances, the , alloys were fabricated by mechanical alloying (MA) and HP. The carrier of p-type SiGe alloy was controlled by B-doping. The effect of sintering condition and thermoelectric properties were investigated. B-doped SiGe alloys exhibited positive seebeck coefficient. The electrical conductivity and thermal conductivity were increased at the small amount of boron content ( at%). However, they were decreased over 0.5 at% boron content. As a result, the small addition of boron improved the Z value. The Z value of 0.5 at% B doped B alloy was , the highest value among the prepared alloys

The present study is to analyze the thermoelectric properties of thermoelectric materials fabricated by the mechanical grinding process. The powders were prepared by the combination of mechanical milling and reduction treating methods using simply crushed pre-alloyed powder. The mechanical milling was carried out using the tumbler-ball mill and planetary ball mill. The tumbler-ball milling had an effect on the carrier mobility rather than the carrier concentration, whereas, the latter on the carrier concentration. The specific electric resistivity and Seebeck coefficient decreased with increasing the reduction-heat-treatment time. The thermal conductivity continuously increased with increasing the reduction-heat-treatment time. The figure of merit of the sintered body prepared by the mechanical grinding process showed higher value than one of the sintered body of the simply crushed powder.