• Journal of the Korean Vacuum Society
• /
• v.15 no.2
• /
• pp.180-185
• /
• 2006

Microwatt power level at relatively high voltage(order of volt) was produced by $Bi_{0.5}Sb_{1.5}Te_{3}/Bi_{2}Te_{2.4}Se_{0.6}$ thin film thermoelectric generators, and maximum output power varied with temperature difference in the square-law relation. Output voltage and current were possible to control by changing the way of electrical connection as well as the number of stacking plate-modules. Variation of open circuit voltage and short circuit current with temperature difference showed a linear relationship. There were, however, some differences in variations; open circuit voltage were dependent on the number of plate-module when connected in series, but it was not for parallel connection. On the other hand, short circuit current showed the opposite behavior to the case of open circuit current.

• Journal of Powder Materials
• /
• v.13 no.5 s.58
• /
• pp.313-320
• /
• 2006

The present study is to analyze the thermoelectric properties of $Bi_{0.4}Sb_{1.6}Te_3$ thermoelectric materials fabricated by the mechanical grinding process. The $Bi_{0.4}Sb_{1.6}Te_3$ powders were prepared by the combination of mechanical milling and reduction treating methods using simply crushed pre-alloyed $Bi_{0.4}Sb_{1.6}Te_3$ 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 $Bi_{0.4}Sb_{1.6}Te_3$ sintered body prepared by the mechanical grinding process showed higher value than one of the sintered body of the simply crushed powder.

• Nuclear Engineering and Technology
• /
• v.55 no.8
• /
• pp.3080-3087
• /
• 2023

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 × 10¹⁰ and 1 × 10¹³ n/cm² by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi₂Te_2.7Se_0.3 and p-type Bi_0.5Sb_1.5Te₃ thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi₂Te_2.7Se_0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi_0.5Sb_1.5Te₃ and n-type Bi₂Te_2.7Se_0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.25 no.4
• /
• pp.135-139
• /
• 2015

$Bi_2Te_3-Bi_2Se_3$ alloy which is typical n-type thermoelectric material were grown by traveling heater method (THM) technique. We investigate the effect of the composition of $100-x(Bi_2Te_3)-x(Bi_2Se_3)$ and doping of n-type dopants such as $SbI_3$ and $CdCl_2$. Maximum figure of merit of $Bi_2Te_3-Bi_2Se_3$ alloy was observed with $CdCl_2$ 0.1 wt% (Z: $2.73{\times}10^{-3}/K$) and $SbI_3$ 0.05 wt% (Z: $2.29{\times}10^{-3}/K$). Deviation along the length of $Bi_2Te_3-Bi_2Se_3$ ingot grown by THM method is low, which indicates that the ingot is very homogenized. Also we observed the close relationship of between anisotropy ratio and dopant in the $90(Bi_2Te_3)-10(Bi_2Se_3)$ alloys. And we confirmed the fact that anisotropy ratio exerts thermoelectric performance in $Bi_2Te_3$ based n-type thermoelectric material.

• Journal of the Microelectronics and Packaging Society
• /
• v.18 no.4
• /
• pp.33-38
• /
• 2011

The p-type $(Bi_{0.2}Sb_{0.8})_2Te_3$ powers were fabricated by mechanical alloying and hot-pressed at temperatures of $350{\sim}550^{\circ}C$. Themoelectric properties of the hot-pressed $(Bi_{0.2}Sb_{0.8})_2Te_3$ were characterized as a function of the hot-pressing temperature. With increasing the hot-pressing temperature from $350^{\circ}C$ to $550^{\circ}C$, the Seebeck coefficient and the electrical resistivity decreased from 237 ${\mu}V/K$ to 210 ${\mu}V/K$ and 2.25 $m{\Omega}-cm$ to 1.34 $m{\Omega}-cm$, respectively. The power factor of the hot-pressed $(Bi_{0.2}Sb_{0.8})_2Te_3$ became larger from $24.95{\times}10^{-4}W/m-K^2$ to $32.85{\times}10^{-4}W/m-K^2$ with increasing the hot-pressing temperature from $350^{\circ}C$ to $550^{\circ}C$. Among the specimens hot-pressed at $350{\sim}550^{\circ}C$, the $(Bi_{0.2}Sb_{0.8})_2Te_3$ hot-pressed at $500^{\circ}C$ exhibited the maximum dimensionless figure-of-merit of 1.09 at $25^{\circ}C$ and 1.2 at $75^{\circ}C$.

• Korean Journal of Materials Research
• /
• v.10 no.4
• /
• pp.257-263
• /
• 2000

Thermoelectric properties of the 0.05wt% $SbI_3$-doped n-type $Bi_2(Te_{0.95}Se_{0.05})_3$ alloy, prepared by melting/grinding and hot pressing, were investigated with variation of the annealing time up to 36 hours. The electron concentration of the 0.05wt% SbI$_3$-doped n-type $Bi_2(Te_{0.95}Se_{0.05})_3$ alloy decreased with increasing the annealing time. The figure-of-merit of the 0.05wt% $SbI_3$-doped n-type $Bi_2(Te_{0.95}Se_{0.05})_3$ alloy was improved from $2.1{\times}10^{-3}/K$ to $2.35{\times}10^{-3}/K$ by annealing at $500^{\circ}C$ for 3 hours. When annealed longer than 12 hours, however, the figure-of-merit decreased substantially due to the increase of the electrical resistivity.

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

• Korean Journal of Materials Research
• /
• v.6 no.7
• /
• pp.678-683
• /
• 1996

In the fabrication processes of thin film thermoelectrics, a subsequent annealing treatment is inevitable to reduce the defects and residual stresses introduced during the film growth, and to make the uniform carrier concentration of the film. However, the diffusion-induced atomic redistribution and the broadening of p/n junction region are expected to affect the thermoelectric properties of thin film modules. The present study intends to investigate the diffusion at the p/n junctions of thermoelectric thin films and to relate it to the property changes. The film junctions of p-type(Bi0.5Sb1.5Te3)and n-type(Bi2Te2.4Se0.6)were prepared by the flash evaporation method. Aluminum thin layer was employed as a diffusion barrier between p-and n-type films of the junction. This was found to be an effective barrier by showing a negligible diffusion into both type films. After annealing treatment, the thermoelectric properties of p/n couples with aluminum barrier layer were accordingly retained their properties without any deterioration.

• Korean Journal of Materials Research
• /
• v.9 no.5
• /
• pp.520-527
• /
• 1999

As a new approache(extrusion-sintering process) to fabricate the thermoelectric materials, it has been at tempted to extrude and sinter the powders simultaneously. It was possible to produce the highly dense <$(Bi,Sb)_2(Te,Se)_3$-based thermoelectrics with sound surface appearances and microstructures by adjusting the process variables. For the p-type materials, the Seeback coefficient was increased with the amount of Te dopants, and the thermoelectric figure of merit appeared to be $2.5\times10^{-3}/K$ at room temperature when doped with 3 at % Te. The n-type specimen doped with 0.16 mol% $SbI_3$ showed the thermoelectric figure of merit of $1.8\times10^{-3}/K$. In both p-type an 우-type materials, the carrier mobility an the thermoelectric figure of merit parallel to the extrusion direction were higher than those perpendicular to it.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2006.09a
• /
• pp.684-685
• /
• 2006

In the present study, the powder metallurgical fabrication of $Bi_{0.4}Te_3Sb_{1.6}$ thermoelectric materials has been studied with specific interest to control the microstructure by the mechanical grinding process. The $Bi_{0.4}Te_3Sb_{1.6}$ thermoelectric powders with a various particle size distribution were prepared by the combination of the mechanical milling and blending processes. The specific electric resistivity of the $Bi_{0.4}Te_3Sb_{1.6}$ sintered bodies mainly depended on the orientation of the crystal structure rather than the particle size of the raw powders.