• Progress in Superconductivity
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• 제1권2호
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• pp.135-140
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• 2000

Distribution of Pr ions between Y- and Ba-site of the $Y(Ba_{1-Xn}Pr_{Xn})_2Cu_3O_y$ ($0{\leq}Xn{\leq}{0.3}$, Xn : nominal composition) material prepared by the solid state reaction method was studied. Although the samples have narrow superconducting transition, tiny peaks of $Y_2BaCuO_5$ impurity phase are included in the x-ray diffraction patterns suggesting that some of the Pr ions are entered into the Y-site. The distribution of Pr ions between Y- and Ba-site was determined by measuring the mass fraction of YBCO and $Y_2BaCuO_5$ phase for each sample through the Rietveld analysis of the x-ray diffraction data. About 60 % of Pr ions occupy the Y-site regardless of the Pr content. Various superconducting parameters such as the oxygen content and the hole concentration etc. are compared before and after the impurity correction.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.250-250
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• 2011

Zinc oxide (ZnO) structures have great potential in many applications. Currently, the most commonly used method to grow ZnO nanostructres are the vapor transport method (VPT). The morphology of the ZnO structures largely related to the growth conditions, including growth temperature, distance between the substrate and source, and gas ambient. Previously ZnO nanosturecutres with high crystallinity were obtained at the growth temperature of 800$^{\circ}C$, in the argon and oxygen gas ambient. In this study, we report the properties of the ZnO nanostructures, which were synthesized on Au-catalyzed Si substrate by VPT, using a mixture of ZnO and graphite powders as source material under the different condition, including gas ratio of argon/oxygen and distance between substrate and source at the growth temperature of 800$^{\circ}C$. The structural and optical properties of the ZnO nanostructures were investigated by field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and photoluminescence (PL).

• Journal of the Korean Ceramic Society
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• 제44권5호
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• pp.151-154
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• 2007

Yttrium aluminum garnet, $Y_3Al_5O_{12}$ (YAG) is an extensively used solid-state laser host material. YAG nanocrystals were synthesized using low-temperature glycol method, a modified sol-gel method performed at low temperature that consists of a mixture of salts that are mostly nitrates in an aqueous media. Single-phase nanocrystalline YAG was obtained at $850^{\circ}C$, which is a much lower temperature than with other techniques such as a wet-chemical technique. The structural characterization is done by powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A crystallite size range of 20-50 nm was observed for the materials prepared at $850-950^{\circ}C$.

• Journal of the Korean Ceramic Society
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• 제35권8호
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• pp.801-806
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• 1998

$Eu^{3+}$ -doped $Y_2$$O_3$ phosphors has been prepared by a polymerized complex method and investigated their powder and luminescence properties. They were compared with phosphors prepared by a solid state reac-thion method. The phosphors synthesized have been characterized by X-ray diffraction low-voltage lu-minescent emission spectroscopy etc. Under low-voltage electron excitation $Eu^{3+}$-doped $Y_2$$O_3$ exhibited a strong narrow-band red emission peaking at 612nm. On the other hand the critical value for concentration quenching of sample prepared by the polymerized complex method fired at $1400^{\circ}C$ is x=0.05 for $(Y_{1-x}Eu_x__2O_3$ The emission intensity of phosphors prepared by the polymerized complex method was higher than that of phosphors prepared by the solid state reaction method.

• Journal of Powder Materials
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• 제22권5호
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• pp.309-314
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• 2015

Tungsten trioxide thin films are successfully synthesized by a sol-gel method using tungsten hexachloride as precursors. The structural, chemical, and optical properties of the prepared films are characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and UV-Vis spectrophotometry. The electrochemical and electrochromic properties of the films before and after heat treatment are also investigated by cyclic voltammetry, chronoamperometry, and in situ transmittance measurement system. Compared to as-prepared films, heat-treated tungsten trioxide thin films exhibit a higher electrochemical reversibility of 0.81 and superior coloration efficiency of $65.7cm^2/C$, which implies that heat treatment at an appropriate temperature is a crucial process in a sol-gel method for having a better electrochromic performance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.75-76
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• 2006

olycrystailine CdSe thin films were grown on ceramic substrate using a chemical bath deposition (CBD)method. They were annealed at various temperature and X-ray diffraction patterns were measured by X-ray diffractometer in order to study CdSe polycrystal structure. Its grain size was about 0.3 ${\mu}m$. Hall effect on this sample was measured by Van der Pauw method and studied on carrier density and movility depending on temperature. We measured also spectral response, sensitivity($\gamma$), maximum allowable power dissipation and response time on these samples.

• Journal of the Korean Magnetics Society
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• 제17권1호
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• pp.18-21
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• 2007

The hexagonal $HoMn_{1-x}-Fe_xO_3$(x=0.00, 0.05) thin films were prepared using pulsed laser deposition(PLD) method on $Pt/Ti/SiO_2/Si$ substrate. The microstructure and magnetic properties have been studied by x-ray diffraction(XRD), atomic force microscopy (AFH), scanning electron microscope(SEM:), x-ray photoelectron spectroscopy(XPS), and conversion electron $M\"{o}ssbauer$ spectroscopy(CEMS). From the analysis of the x-ray diffraction patterns, the crystal structure for all films was found to be a hexagonal($P6_3cm$), which was preferentially grown along(110) direction. The lattice constant $c_0$ of the film with x=0.05 was close to that of single crystal, whereas lattice constant $a_0$ with respect to single crystal shows a slight decrease. This difference of lattice parameters between film and single crystal was caused by the lattice mismatch between the film and $Pt/Ti/SiO_2/Si$ substrate. Conversion electron $M\"{o}ssbauer$ spectrum of $HoMn_{0.95}Fe_{0.05}O_3$ thin film shows an asymmetry doublet absorption ratio at room temperature, which is due to the oriented direction of crystallographic domains. This is corresponding with analysis of x-ray diffraction. The quadrupole splitting(${\Delta}E_Q$) at room temperature is found to be $1.62{\pm}0.01mm/s$. This large ${\Delta}E_Q$ was caused by asymmetry environment surrounding Fe ion.

• Journal of the Korean Ceramic Society
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• 제42권5호
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• pp.299-303
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• 2005

The crystal structure and ferroelectricity of the $(1-x)BiFeO_3\;(BF)-xPbTiO_3$ (PT) ceramic system with the addition of $DyFeO_3$ (DF) have been investigated for attaining a high temperature piezoelectric material. This study is focused on the relation between crystal structure and ferroelectric property with the addition of DF over the phase boundary in the (1-x)BF-xPT system. Hysteresis curves of polarization-electric field at room temperature have been measured. The X-ray and neutron diffraction data were analyzed by the rietveld refinement method. The addition of 0.1 mole DF into BF-PT system greatly increases the ferroelectric remanant polarization Pr values, e.g. 17 ${\mu}C/cm^2$ in 0.6BF-yDF-(0.4-y)PT and 31${\mu}C/cm^2$ in 0.5BF-yDF-(0.5.y)PT, respectively. The improved Pr value has been discussed in relation with crystal structure and electrical property.

• Proceedings of the Korean Society of Medical Physics Conference
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• 한국의학물리학회 2002년도 Proceedings
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• pp.407-410
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• 2002

Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. There are several methods to produce such monochromatic x-rays. The most popular one is crystal diffraction monochromatization, which has been commonly used because of the fact that the energy spread is very narrow and the energy can be changed continuously. The alternative method is the use of fluorescent x-ray, which has several advantages such as large beam size and fast energy change. We have developed a parallel-beam and a fan-beam monochromatic x-ray CT, and compared some characteristics such as accuracy of CT numbers between those systems. The fan beam monochromatic x-rays were generated by irradiating target materials by incident white x-rays from a bending magnet beam line NE5 in 6.5 GeV Accumulation Ring at Tukuba. The parallel beam monochromatic x-rays were generated by using a silicon double crystal monochromator at the bending magnet beam line BL-20BM in Spring-8. A Cadmium telluride (CdTe) 256 channel array detector with 512mm sensitive width capable of operating at room temperature was used in the photon counting mode. A cylindrical phantom containing eight concentrations of gadolinium was used for the fan beam monochromatic x-ray CT system, while a phantom containing acetone, ethanol, acrylic and water was used for the parallel monochromatic x-ray CT system. The linear attenuation coefficients obtained from CT numbers of those monochromatic x-ray CT images were compared with theoretical values. They showed a good agreement within 3%. It was found that the quantitative measurement can be possible by using the fan beam monochromatic x-ray CT system as well as a parallel beam monochromatic X-ray CT system.

• Korean Journal of Food Science and Technology
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• 제30권5호
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• pp.1024-1028
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• 1998

Crystalline structure of the extrudate of high amylose corn starch was studied by X-ray diffractometer and $^{13}C\;NMR$. The X-ray diffraction crystal ratio of the extrudates (barrel temperature $100^{\circ}C$ )of high amylose corn starch slightly increased from 6.08% to 8.37% by increasing feed moisture content from 25% to 45%. But extrudates of high amylose corn starch showed similar crystal ratio on various extrusion conditions. Extrudates of high amylose corn starch (feed moisture content 20%, barrel temp $140^{\circ}C$) showed more enlarged crystal structure than that of non-extrudates. The perpendicular distance of crystal increased by extrusion. Crystal ratio was changed from $6.3{\sim}8.3%$ to $4.5{\sim}5.8%$ during storage at $4^{\circ}C$. Starch configuration was examined with $^{13}C\;NMR$. Double helical content was measured by $^{13}C\;NMR$ method. The highest double helical content (60%) was obtained from high amylose corn starch extrudate (barrel temp.: $100^{\circ}C$, feed moisture content 45%). Double helical contents and resistant starch (RS) yield (pancreatin) were positively correlated. However, double helical content of the extrudates was not changed by the storage at $4^{\circ}C$.