• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.227-250
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• 1999

The reproducibility of successive growth of Bi12TiO20(BTO) single crystals using a top-seeded solution growth (TSSG) pulling method was evaluated by measuring the lattice constants and their standard deviations. A substantial phase diagram in the region close to the stoichiometric BTO was established experimentally for this purpose, and the existence of a retrograde solid solution close to a BTO was clarified. It was emphasize that a starting solution, with a 10.0~10.1 mol% TiO2 concentration, results in large single crystals with a highly homogeneous lattice constant of within $\pm$1x10-4$\AA$, when the solidified fraction of the grown crystal is less than about 45%. A wavelength dispersion of refractive index was measured for the first time, an it was verified that the refractive index of BTO is larger than that of BSO(Bi12TiO20), allowing the voltage sensitivity of EOS higher than the case with BSO as a probe head.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.583-586
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• 2003

BiSrCaCuO superconducting thin films have been fabricated by co-deposition using the faraday cup. Despite setting the composition of thin film Bi2212, Bi(2201, 2212, 2223) phase were appeared. It was confirmed the obtained field of stabilizing phase was represented in the diagonal direction of the right below end in the Arrhenius plot of temperature of the substrate and $PO_3$, and it was distributed in the rezone.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.07a
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• pp.585-586
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• 2005

BSCCO thin films were fabricated by an ion beam sputtering method with an ultra-low growth rate, and sticking coefficients of the respective elements are evaluated. The sticking coefficient of Bi element in BSCCO film formation was observed to show a unique temperature dependence; it was almost a constant value of 0.49 below about $730^{\circ}C$ and decreased linearly over about $730^{\circ}C$. In contrast, Sr and Ca, displayed no such remarkable temperature dependence. This behavior of the sticking coefficient was explained consistently on the basis of the evaporation and sublimation processes of Bi2O3. It is considered that the liquid phase of the bismuth oxide plays an important role in the Bi 2212 phase formation in the co-deposition process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.12
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• pp.803-808
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• 2014

$Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics with an excess $Bi^{3+}$ and a deficiency of $Na^+$ and $K^+$ were synthesized by a conventional solid state reaction method. The structure and morphology of $Bi_{0.5+x}(Na_{0.78}K_{0.22})_{0.5-3x}TiO_3$ ceramics were characterized by X-ray diffraction and field emission scanning electron microscopy. The electric polarization and mechanical strain induced by external electric field, and the temperature dependence of dielectric constant were investigated. These results demonstrated that an ergodic relaxor phase can be induced by controls of the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. A phase boundary between non-ergodic and ergodic relaxor phases can be observed at ambient temperature. The ergodic relaxor phase can be transferred to the ferroelectric phase by application of the electric field. The stability of the induced ferroelectric phases strongly depends on the mole ratio of $Bi^{3+}$, $Na^+$ and $K^+$. The maximum strain of 0.31% was observed in $Bi_{0.51}(Na_{0.78}K_{0.22})_{0.47}TiO_3$ ceramics sintered at $1,150^{\circ}C$ for 2 h.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.59-59
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• 2011

We will report atomically sharp epitaxial growth of $Bi_2Se_3$ three-dimensional topological insulator films on Si(111) substrate with molecular beam epitaxy (MBE). It was achieved by employing two step growth temperatures to prevent any formation of second phase, like as $SiSe_2$ clusters, between $Bi_2Se_3$ and Si substrate at the early stage of growth. The growth rate was determined completely by Bi flux and the Bi:Se flux ratio was kept ~1:15. The second-phase-free atomically sharp interface was verified by RHEED, TEM and XRD. Based on the RHEED analysis, the lattice constant of $Bi_2Se_3$ relaxed to its bulk value during the first quintuple layer implying the absence of strain from the substrate. Single-crystalline XRD peaks of $Bi_2Se_3$ were observed in films as thin as 4 QL. TEM shows full epitaxial structure of $Bi_2Se_3$ film down to the first quintuple layer without any second phases. This growth method was used to grow high quality epitaxial $Bi_2Se_3$ films from 3 QL to 3600 QL. The magneto-transport properties of these thin films show a robust 2D surface state which is thickness independent.

• Journal of Sensor Science and Technology
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• v.25 no.1
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• pp.1-7
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• 2016

Bioelectrical impedance (BI) at popliteal regions was measured using a bioelectrical impedance measurement system (BIMS), which employs the multi-frequency and the two-electrode method. Experiments were performed as follows. First, a constant AC current of $800{\mu}A$ was applied to the popliteal regions (left and right) and the BI was measured at eight different frequencies from 10 to 500 kHz. When the applied frequency greater than 50 kHz was applied to human's popliteal regions, the BI was decreased significantly. Logarithmic plot of impedance vs. frequency indicated two different mechanisms in the impedance phenomena before and after 50 kHz. Second, the relationship between resistance and reactance was obtained with respect to the applied frequency using BI (resistance and reactance) acquired from the popliteal regions. The phase angle (PA) was found to be strongly dependent on frequency. At 50 kHz, the PA at the right popliteal region was $7.8^{\circ}$ slightly larger than $7.6^{\circ}$ at the left popliteal region. Third, BI values of extracellular fluid (ECF) and intracellular fluid (ICF) were calculated using BIMS. At 10 kHz, the BI values of ECF at the left and right popliteal regions were $1664.14{\Omega}$ and $1614.08{\Omega}$, respectively. The BI values of ECF and ICF decreased sharply in the frequency range of 10 to 50 kHz, and gradually decreased up to 500 kHz. Logarithmic plot of BI vs. frequency shows that the BI of ICF decreased noticeably at high frequency above 300 kHz because of a large decrease in the capacitance of the cell membrane.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.41-41
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• 1993

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.371-374
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• 2002

Bismuth lanthanum titanate thin films with excess Bi contents were prepared onto Pt/Ti/$SiO_2$/Si substrate by metalorganic decomposition (MOD) technique. The structure and morphology of the films were analyzed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. From the XRD analysis, BLT thin films show polycrystalline structure and the layered-perovskite phase was obtained over 10% excess of Bi contents. As a result of ferroelectric characteristics related to the Bi content of the BLT thin film, the remanent polarization and dielectric constant decreased with increasing over Bi content of 10 % excess. The BLT film with Bi content of 10% excess was measured to have a dielectric constant of n9 and dielectric loss of 1.85[%]. The BLT thin films showed little polarization fatigue test up to 3.5 x $10^{9}$ bipolar switching cycling.

• Journal of the Korean Ceramic Society
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• v.38 no.12
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• pp.1104-1109
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• 2001

Samples with the nominal composition, B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$C $a_{2.03}$C $u_{3.06}$ $O_{10+}$$\delta$/ high $T_{c}$ superconductors containing As as an additive were fabricated by a solid-state reaction method. Samples with Ag of 10wt%, 30 wt% and 50 wt% each were sintered at 86$0^{\circ}C$~875$^{\circ}C$ for 24 hours. The structural characteristics, critical temperature and grain size with respect to Ag contents were analyzed by XRD(X-ray Diffraction) and SEM(Scanning Electron Microscope), respectively. As Ag contents increased, XRD peaks of g in Bi-2223 phase superconductors intensified and the proportion of the phase transition from Bi-2223 to Bi-2212 was increased.increased.

• Journal of the Mineralogical Society of Korea
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• v.13 no.1
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• pp.44-52
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• 2000

천연에서 발견되는 geversite (PtSb2), stumpflite (PtSb), insizwaite (PtBi2), unnamed PtBi 등의 광물에 대한 안정영역과 원소치환에 따른 고용체 존재를 규명하기 위해 백금-안티모니-비스머스 등 3성분계에 대한 합성실험적 연구를 실시하였다. 이번 연구에서 설정된 $600^{\circ}C$ 온도의 실험결과에 의하면, 등축정계의 geversite와 insizwaite 사이에 완전고용체가 형성되며, Sb를 치환하는 Bi의 함량에 따라 단위포 상수는 6.4415(0 at.%), 6.4361(15 at.%), 6.5204(30 at.%), 6.5411(51 at.%), 6.6261(70 at%), 6.6540(85 at%), 6.728$\AA$(100 at.%)로 증가함을 알 수 있었다. 육방정계인 stumpflite와 unnamed PtBi 사이에도 완전고용체가 형성되며, Sb를 치환하는 Bi의 함량이 증가함에 따라 a 단위포 상수의 크기는 4.1388(0 at.%), 4.2118(20 at.%), 4.2118(40 at.%), 4.2485(80 at.%), 4.3242$\AA$(100 at.%)등 연속적으로 증가하지만, c 단위포 상수는 각각 5.4902, 5.4799, 5.508, 5.4817, 5.5045$\AA$등 불규칙하게 변함을 알 수 있었다. 0~33.33 at.% Pt 영역에서의 상평형 관계는 액체가 Pt(Sb,Bi)2 고용체와 공존하고 있고, Sb가 많이 함유된 액체에서는 geversite+원소광물 안티모니+백금이 거의 함유되지 않은 액체와 공생하는 3-phase assemblage를 형성한다. 자연계에서는 geversite와 insizwaite 및 stumpflite와 unnamed PtBi 사이의 화학조성을 가지는 광물이 발견되고 있는데, 이들은 각각 독립적인 광물종이 아니라 위 광물들의 고용체에 속하는 것임을 알 수 있었다. 이들 광물을 명명하고 해석하는데 매우 세심한 주의가 필요함을 알 수 있었다. 또한 단위포 상수를 측정을 통해 해당 고용체 광물의 Sb↔Bi 치환 양을 추정할 수 있다는 점과 광물 공생관계를 통해 생성온도를 추정할 수 있다는 사실을 알 수 있었다.