• Journal of the Korean Vacuum Society
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• v.14 no.4
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• pp.215-221
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• 2005

Thermoelectric bismuth telluride thin films were prepared on $SiO_{2}$/Si substrate with co-sputtering of bismuth and tellurium targets. The effects of deposition temperature on surface morphology, crystallinity and electrical transport properties were investigated. Hexagonal crystallites were clearly visible at the surface of films deposited above $290 ^{\circ}C$. Change of dominant phase from rhombohedral $Bi_2Te_3$ to hexagonal BiTe was confirmed with X-ray diffraction analysis. The deviation from stoichiometric composition at high deposition temperature resulted in the change of structural and electrical characteristics. Seebeck coefficients of all samples have negative value, indicating the prepared $Bi_XTe_Y$ films are n-type thermoelectric. Optimum of Seebeck coefficient and power factor were obtained at the deposition temperature of $225 \^{circ}$C (about -55 $\mu$V/K and $3\times10^{-4}$ W/$k^{2}$m, respectively). Deterioration of thermoelectric properties at higher temperature.

• Proceedings of the Materials Research Society of Korea Conference
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• 2005.05a
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• pp.278-278
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• 2005

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2006.10a
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• pp.86-86
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• 2006

• Korean Journal of Optics and Photonics
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• v.1 no.1
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• pp.16-21
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• 1990

The accurate polarization state of the light inside BSO crystal was calculated with consideration of optical activity. By solving Maxwell's equations, the general form of the polarization matrix for any direction of the electric field was obtained. Examples of output polarization states in BSO crystals were also calculated, and their properties were discussed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.3
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• pp.622-629
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• 1988

In order to improve the sensitivity of the wafer type heat flux sensor, some heat flux sensors were manufactured and examined by using thermoelectric semiconductor material (bismuth telluride) whose Seebck coefficient is much larger than those of metallic thermocouple materials. Because the thermoelectric element cannot be bended or welded, a peculiar sensor structure and manufacturing process were designed. As a result, it is revealed that the characteristic sensitivity of the manufactured sensor is about 10 times larger than that of marketed sensor even though there are some troubles in stiffness for reciprocal use. If we make this kind of sensors smaller and thinner, it will be a useful method to measure the local heat flux from the surface of complex configuration.

• Resources Recycling
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• v.20 no.2
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• pp.60-66
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• 2011

Solvent extraction experiments were carried out to recover and separate Ru(III) from aqueous hydrochloric acid media using TBP and Cyanex923. The efficiency of the extraction was studied under various experimental conditions, such as concentration of HCl and NaCl, concentration of extractant in the organic phase and temperature. The extraction behavior of metal impurities, such as Pt, Bi, Sn, Fe, Pb and Cu in mixed solutions was examined. From the experimental studies, it was found that the Cyanex923 resulted in higher extraction percentage of Ru than TBP. However TBP was more effective for the separation of Ru and Pt, Bi, Sn in mixed solutions than Cyanex923.

• Journal of radiological science and technology
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• v.41 no.6
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• pp.611-616
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• 2018

Lead apron is harmful to the human body because it is made at heavy metals, and when worn for long periods of time, it causes pain. Therefore, this paper intended to improve the defects of lead apron by using new material shields. For the comparative evaluation of lead and new material shieldes, the shielding rate and weight were measured and tested based on lead 0.5 mmPb. The rate of shielding was 97% based on lead at 0.5 mm thickness, while The new material shield T3 showed similar shielding rates as lead in 8 layers, and in T2 these values were measured in 11 layers. In addition, similar shielding rate was measured in 12 layers at B2, and 8 layers in BF, and 4 layers in $BF_2$. Comparing the weight of cases when commercialized with apron, T3, T2 and B2 were heavier than lead apron. But BF, $BF_2$ were lighter than the lead apron. Based on the results of the experiment, T3 and T2 can be used as an alternative to lead if human or environmental hazards are considered a priority. However, BF and $BF_2$ should be used if the reduction of external exposure is considered a priority.

• Journal of the Korean Magnetics Society
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• v.26 no.2
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• pp.39-44
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• 2016

Determination of the structural, electronic, and magnetic properties of the magnetically doped bismuth-telluride alloys are drawing lots of interest in the fields of the thermoelectric application as well as the research on magnetic interaction and topological insulator. In this study, we performed the first-principles electronic structure calculations within the density functional theory for the Gd doped bismuth-tellurides in order to study its magnetic properties and magnetic phase stability. All-electron FLAPW (full-potential linearized augmented plane-wave) method is employed and the exchange correlation potentials of electrons are treated within the generalized gradient approximation. In order to describe the localized f-electrons of Gd properly, the Hubbard +U term and the spin-orbit coupling of the valence electrons are included in the second variational way. The results show that while the Gd bulk prefers a ferromagnetic phase, the total energy differences between the ferromagnetic and the antiferromagnetic phases of the Gd doped bismuth-telluride alloys are about ~1meV/Gd, indicating that the stable magnetic phase may be changed sensitively depending on the structural change such as defects or strains.

• Journal of the Korean Society of Radiology
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• v.13 no.7
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• pp.969-977
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• 2019

Applying the bismuth shield used to reduce the radiation exposure, image quality may be reduced due to beam hardening caused by the shield during CT scan. Therefore, we tried to find out the energy range that can reduce image degradation by applying GSI mode of G company's dual energy CT and examine the possibility through experiment. As a result, after bismuth shielding, 118 ± 10.6 HU and 50.1 ± 14.6 HU at 50 keV after dual-energy CT scan were the most similar to the CT value before image deterioration(p> 0.05). It was measured 176.6 ± 7.1 and 138.3 ± 1.1 at 50 keV(p> 0.05). Experiments showed that the use of the shield during CT inspection inevitably degrades the image quality, but experiments show that the GSI function of the dual energy CT can maintain the image quality even when the shield is used. If the various shields are secured after the evaluation using the dual energy CT, it is expected to overcome the disadvantages of poor image quality caused by the use of the radiation shield for reducing the exposure, which is the biggest disadvantage of the CT scan.

• Journal of the Korean Magnetics Society
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• v.23 no.1
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• pp.1-6
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• 2013

Spin-orbit coupling (SOC) effect is known to be the physical origin for various exotic magnetic phenomena in the low-dimensional systems. Recently, SOC also draws lots of attention in the study on magnetically doped thermoelectric alloys to determine their properties as the thermoelectric application as well as the topological insulator via the exact electronic structures determination near the Fermi level. In this research, aiming to investigate the spin-orbit coupling effect on the structural properties such as the lattice constants and the bulk modulus of the most widely investigated thermoelectric host material, $Bi_2Te_3$, we carried out the first-principles electronic structure calculation using the all-electron FLAPW (full-potential linearized augmented plane-wave) method. Employing both the local density approximation (LDA) and the generalized gradient approximation (GGA), the structural optimization is achieved by varying the in-plane lattice constant fixing the perpendicular lattice constant and vice versa, to find that the SOC effect increases the equilibrium lattices slightly in both directions while it markedly reduces the bulk modulus value implying the strong orientational dependence, which are attributed to the material's intrinsic structural anisotropy.