• Journal of Powder Materials
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• v.23 no.2
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• pp.126-131
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• 2016

The recent rise in applications of thermoelectric materials has attracted interest in studies toward the fabrication of thermoelectric materials using mass production techniques. In this study, we successfully fabricate n-type $Bi_2Te_{2.7}Se_{0.3}$ material by a combination of mass production powder metallurgy techniques, gas atomization, and spark plasma sintering. In addition, to examine the effects of hydrogen reduction in the microstructure, the thermoelectric and mechanical properties are measured and analyzed. Here, almost 60% of the oxygen content of the powder are eliminated after hydrogen reduction for 4 h at $360^{\circ}C$. Micrographs of the powder show that the reduced powder had a comparatively clean surface and larger grain sizes than unreduced powder. The density of the consolidated bulk using as-atomized powder and reduced atomized powder exceeds 99%. The thermoelectric power factor of the sample prepared by reduction of powder is 20% better than that of the sample prepared using unreduced powder.

• Advances in materials Research
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• v.9 no.3
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• pp.171-187
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• 2020

The microstructural evolution of different compositions of Mg-Sn alloys (30%Sn-70%Mg, 40%Sn-60%Mg and 50%Sn-50%Mg) is studied at first to understand the changes observed with change in tin content and deformation conditions. The Mg₂Sn phase increases with increase in tin content and a significant substructure development is found in 50%Sn-50%Mg alloy. The above observation led to further deformation studies on Mg₂Sn based thermoelectric materials with higher tin percentage. The microstructure in terms of Electron backscatter diffraction (EBSD)measurements is studied in detail followed by the determination of thermoelectric properties i.e., Seebeck coefficient and electrical conductivity for both as cast and extruded Mg_(2+x)Sn-Ag alloys. The electrical conductivity of the extruded Mg_(2+x)Sn-.3wt%Ag {x =1} alloy was found to be more than its as cast counterpart while the Seebeck coefficient values remained almost the same.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.430-431
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• 2006

Thermoelectric thick film was fabricated by screen printing process with using p-type Bi-Te-Sb powders. The powder was synthesized by melting, milling and sintering process and hydrogen reduced to enhance the thermoelectric property. The thick film of Bi-Te-Sb powder was fabricated by screen printing method and baked at the optimized conditions. The thermal conductivity, the electrical resistivity and Seeback coefficient of thick film were measured and the thermoelectric performance was analyzed in terms of film characteristics and its microstructure. Finally, the feasibility of thermoelectric thick film into micro cooling device on CPU chip was discussed in this study.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.05a
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• pp.525-527
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• 2008

N-Type $SbI_3$-doped $95%{Bi_2}{Te_3}-5%{Bi_2}{Se_3}$ compounds were prepared by a gas atomization and Magnetic Pulsed Compaction process. The dynamic recrystallization and thermoelectric properties of the MPCed bulks with consolidation temperatures and times were investigated by a combination of microscopy, XRD and thermoelectric property testing. The microstructure of MPCed bulk shows homogeneous and fine distribution through consolidated bulks due to dynamic recrystallization during hot MPC. This research presented the challenges toward the successful consolidation of thermoelectric powder using magnetic pulsed compaction (MPC).

• Korean Journal of Materials Research
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• v.27 no.8
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• pp.438-444
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• 2017

In this work, the effects of hydrogen reduction on the microstructure and thermoelectric properties of $(GeTe)_{0.85}(AgSbTe_2)_{0.15}$ (TAGS-85) were studied by a combination of gas atomization and spark plasma sintering. The crystal structure and microstructure of TAGS-85 were characterized by X-ray diffraction(XRD) and scanning electron microscopy (SEM). The oxygen content of both powders and bulk samples were found to decrease with increasing reduction temperature. The grain size gradually increased with increasing reduction temperature due to adhesion of fine grains in a temperature range of 350 to $450^{\circ}C$. The electrical resistivity was found to increase with reduction temperature due to a decrease in carrier concentration. The Seebeck coefficient decreased with increasing reduction temperature and was in good agreement with the carrier concentration and carrier mobility. The maximum power factor, $3.3{\times}10^{-3}W/mK^2$, was measured for the non-reduction bulk TAGS-85 at $450^{\circ}C$.

• Proceedings of the Materials Research Society of Korea Conference
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• 1996.11a
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• pp.43-43
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• 1996

• Journal of Powder Materials
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• v.23 no.2
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• pp.120-125
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• 2016

P-type ternary $Bi_{0.5}Sb_{1.5}Te_3$ alloys are fabricated via mechanical alloying (MA) and spark plasma sintering (SPS). Different ball sizes are used in the MA process, and their effect on the microstructure; hardness, and thermoelectric properties of the p-type BiSbTe alloys are investigated. The phases of milled powders and bulks are identified using an X-ray diffraction technique. The morphology of milled powders and fracture surface of compacted samples are examined using scanning electron microscopy. The morphology, phase, and grain structures of the samples are not altered by the use of different ball sizes in the MA process. Measurements of the thermoelectric (TE) transport properties including the electrical conductivity, Seebeck coefficient, and power factor are measured at temperatures of 300-400 K for samples treated by SPS. The TE properties do not depend on the ball size used in the MA process.

• Journal of Powder Materials
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• v.15 no.5
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• pp.345-351
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• 2008

The effects of the dopant (Mn) ratio on the microstructure and thermoelectric properties of $FeSi_2$ 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 ${\varepsilon}-FeSi$ 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 ${\alpha}-Fe_{2}Si_{5}$, ${\varepsilon}-FeSi$ and ${\beta}-FeSi_2$ phase. The semiconducting phase of ${\beta}-FeSi_2$ was transformed from ${\alpha}-Fe_{2}Si_{5}+{\varepsilon}-FeSi$ phase by annealing.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.28-28
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• 2005

• Archives of Metallurgy and Materials
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• v.65 no.3
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• pp.1105-1110
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• 2020

Due to air pollution, global warming and energy shortage demands new clean energy conversion technologies. The conversion of industrial waste heat into useful electricity using thermoelectric (TE) technology is a promising method in recent decades. Still, its applications are limited by the low efficiency of TE materials in the operating range between 400-600 K. In this work, we have fabricated Cu_0.005Bi_0.5Sb_1.495Te₃ powder using a single step gas atomization process followed by spark plasma sintering at different temperatures (623, 673, 723, and 773 K), and their thermoelectric properties were investigated. The variation of sintering temperature showed a significant impact on the grain size. The Seebeck coefficient values at room temperature increased significantly from 127 µVK to 151 µV/K with increasing sintering temperature from 623 K to 723 K due to decreased carrier concentration. The maximum Z T values for the four samples were similar in the range between 1.15 to 1.18 at 450 K, which suggest these materials could be used for power generation in the mid-temperature range (400-600 K).