• Electrical & Electronic Materials
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• v.11 no.11
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• pp.46-52
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• 1998

Barium titanate owes its great importance to the fact that its dielectric constant is about 100 times higher than that of conventional dielectric materials provided its compositional and structural purity is extremely high. The value of crystalline BaTiO3 bodies as used, for instance, in computer elements, magnetic amplifiers, memory device, ets., depend on boththe compositional and the structural purity of the BaTiO3 crystals. This purity will, in turn, depend on the purity of the raw materials used in manufacturing the BaTiO3 compound and on the particularmethods of manufacture which determine the size, homogeneity, and the structural purity of the crystals. This paper reviews the important theoretical considerations, processing techniques and applications related to sol-gel derived thin films.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.57-63
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• 2017

High-purity ${\beta}-SiC$ powders for SiC single-crystal growth were synthesized by direct carbonization. The use of high-purity raw materials to improve the quality of a SiC single crystal is important. To grow SiC single crystals by the PVT method, both the particle size and the packing density of the SiC powder are crucial factors that determine the sublimation rate. In this study, we tried to produce high-purity ${\beta}-SiC$ powder with large particle sizes and containing low silicon by introducing a milling step during the direct carbonization process. Controlled heating improved the purity of the ${\beta}-SiC$ powders to more than 99 % and increased the particle size to as much as ${\sim}100{\mu}m$. The ${\beta}-SiC$ powders were characterized by SEM, XRD, PSA, and chemical analysis to assess their purity. Then, we conducted single-crystal growth experiments, and the grown 4H-SiC crystals showed high structural perfection with a FWHM of about 25-48 arcsec.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.491-493
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• 2002

Liquid chromatographic direct resolution of racemic naphthyl propionate liquid crystals were successful on a commercial chiral column, (S,S)-Whelk-O1. The very simple procedure can be applied to the intermediate and final products without any structural modification.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.190.2-190.2
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• 2013

Vanadium dioxide ($VO_2$) has been widely attracted for academic research and industrial applications due to its metal-insulator transition (MIT) temperature close to room temperature. We synthesized VOx film on (0001) sapphire substrate with vanadium target (purity: 99.9%) using DC magnetron sputtering in Ar ambience at a pressure of $10^{-3}$ Torr at $400{\sim}700^{\circ}C$. The VOx film subsequently was annealed at difference temperatures in ambience of Ar and $O_2$ gas mixture at $60{\sim}800^{\circ}C$. The structural properties of the films were investigated using scanning electron microscopic (SEM), x-ray diffraction (XRD) and x-ray absorption fine structure (XAFS) measurements. SEM reveal that small grains formed on the substrates with a roughness surface. XRD shows oriented $VO_2$(020) crystals was deposited on the $Al_2O_3$(006) substrate. From I-V measurements, the electric resistance near its MIT temperature were dramatically changed by ${\sim}10^4$ during heating and cooling the films. We will also discuss the temperature-dependent local structural changes around vanadium atoms using XAFS measurements.