• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.70-76
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• 1987

The effect of C12A7 and OH group on the synthesis of C3A by the sol-gel process using aluminum-sec-butoxide and calcium nitrate was studied. C3A by sol-gel method was compared with C3A obtained by the conventional method with respect to their reactivity of formation and crystal size. The sol-gel process for initial formation of C12A7 and C3A at lower temperature (1100, 1200$^{\circ}C$) was superior, but that for complete crystallization of C3A at higher temperature (1300, 1400$^{\circ}C$) was inferior to oxide mixture process. When heat treated under the atmosphere oxygen-free dried nitrogen eliminate the influence of OH group in C12A7, the reactivity of C3A from sol-gel sample incorporated OH group were poor, whereas that from oxide mixture sample showed remarkable effect. The poor crystallization of C3A at higher temperature is presumed to be due to the fact that incorporated OH group in C12A7 formed at lowr temperature might interrupt the diffusion of CaO to C12A7 to from C3A. The crystal size and the hydration characteristics of both C3A obtained by different processes exhibited almost the same results.

• Journal of the Korean Ceramic Society
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• v.34 no.1
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• pp.37-44
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• 1997

Barium ferrite thin films on the thermal oxidized Si substrate were prepared by using sol-gel method (dip coating) from the sol of composition ratio of 5.25, designated by mole ratio 2Fe/Ba. The gelation process was largely divided into 4 step, and the sol prepared by reaction for 90 minutes at 8$0^{\circ}C$ was the suit-able for coating. Needle shaped particles formed on the coating layer were placed parallel to substrate and the inclination was increased with film thickness. The easy-direction of magnetization of needle shaped par-ticles was long-axis direction.

• Journal of the Korean Ceramic Society
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• v.34 no.9
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• pp.993-1001
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• 1997

The (0.8PPV+0.2DMPPV) copolymer and silica/borosilicate composites were synthesized by sol-gel process. The organic-inorganic hybrid solution was prepared by using of (0.8PPV+0.2DMPPV) copolymer precursor solution as a raw material for organic components and TEOS and TMB for glass components. Then by drying the solution in vacuum at 5$0^{\circ}C$ for 7days and subsequent heat treatment in vacuum at 15$0^{\circ}C$~30$0^{\circ}C$ for 2h~72h with heating rate of 0.2$^{\circ}C$/min and 1.8$^{\circ}C$/min, the organic-inorganic composites were synthesized. Microstructural evolution of the composites was characterized by DSC, IR spectrocopy, UV/VIS spectroscopy, and TEM. Elimination of the polymer precursor and degradation of the polymer were observed by DSC and Si-O and trans C=C absorption peaks were identified by IR spectra. The polymer was found to be successfully incorporated into the glass matrix and it was confirmed by the absorption peaks from the polymer in the UV/VIS spectra and the TEM results. The absorption peak of the composites was found to shift toward short wavelength side compared to that of the pure polymer and the amount of the blue shift increased with increasing the heat treatment temperature and heat treatment time and with decreasing the heating rate.

• Journal of the Korean Ceramic Society
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• v.29 no.1
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• pp.29-34
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• 1992

Phase transition, dielectric properties, and leakage current characteristics of Ta2O5 thin film fabricated by sol-gel process with tantalum penta-n-butoxide were studied as a function of annealing temperature in O2 atmoshpere. Although Ta2O5 thin film annealed at temperatures below 700$^{\circ}C$ for 1 hr was amorphous, it was crystallized to ${\beta}$-Ta2O5 of orthorhombic phase by annealing at temperatures higher than 750$^{\circ}C$. With increasing annealing temperature from 500$^{\circ}C$ to 900$^{\circ}C$, dielectric constant of sol-gel processed Ta2O5 thin film was changed from 17.6 to 15.3 due to the increase of SiO2 thickness at Ta2O5/Si interface. For Ta2O5 thin film annealed at 500$^{\circ}C$ to 800$^{\circ}C$ for 1 hr in O2 atmosphere, leakage current was remarkably reduced and breakdown strength was increased with higher annealing temperature. For Ta2O5 film annealed at 800$^{\circ}C$, breakdown did not occur even at electric field strength of 30${\times}$105V/cm and leakage current was maintained lower than 10-8A/$\textrm{cm}^2$.

• Journal of the Korean Applied Science and Technology
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• v.18 no.3
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• pp.233-240
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• 2001

The transparent organic-inorganic hybrid films were prepared by the Sol-Gel process. PVP(polyvinylpyrrolidone) was used in organic component and TEOS(tetraethoxysilane) was used in inorganic component. HCI, $CH_{3}COOH$, and $NH_{4}OH$ were used as the Sol-Gel catalyst. The characteristics according to not only the variation of organic and inorganic contents but also the variation of catalyst species and contents were investigated. On the whole, the compatibility was remained between organic and inorganic components, and also as the TEOS contents were increased, mostly the transparency and the mechanical, thermal properties were improved. In addition, as content of catalysts was increased, the films showed characteristics that were closer to PVP than silica. Although the transparency of films was preserved in HCI and $CH_{3}COOH$, only the film containing more than 40wt% TEOS in $NH_{4}OH$ showed different phenomena.

• Journal of the Korean Ceramic Society
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• v.33 no.12
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• pp.1301-1310
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• 1996

Generally it requires high sintering temperatures more than 135$0^{\circ}C$ to make semiconductive BaTiO3 ceramics. Also it is very difficult to achieve a homogeneous mixing in solid-state reaction method. Therefore the liquid phase distributed to non-uniform dilute the characteristics of PTCR. In order to improve the uniformity this study is used the sol-gel coating method. Using this method we studied the new manufacturing process that had a high reproducibility and mass production capability. Tetraethyl orthosilicate (TEOS) was used as a source of Si. The semiconductive BaTiO3 ceramics which was produced by sol-gel method for the SiO2 addition and sintered between 124$0^{\circ}C$ and 130$0^{\circ}C$ showed almost same resistivity at room temperature among 125$0^{\circ}C$ and 130$0^{\circ}C$. As the results We could be sintered the semiconducting BaTiO3 ceramics at lower temperature even at 125$0^{\circ}C$ maintaining the same specific resistivity ratio ($\rho$max/$\rho$min) at 130$0^{\circ}C$. The specific resistivity both below and above the Curie temperature were increased by slow cooling and the steepness of the plots in the reasion of transition from low to high resistance increased as the cooling rate decreased.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.6
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• pp.262-266
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• 2010

The Calcium-aluminate electride thin films on the quartz substrates was coated by sol-gel process. The crystallization of the C12A7 thin film was observed at $800^{\circ}C$ and high density C12A7 thin film was achieved on heat treatment at $1,200^{\circ}C$ for 1 hour. The reduction heat treatment of C12A7 thin film could be converted from insulator to conductor and the electrical conductivity was 120 S/cm in the C12A7 thin film heat treated at $1,200^{\circ}C$ with $H_2$ gas for 48 hours.

• Resources Recycling
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• v.17 no.5
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• pp.52-59
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• 2008

Sol-gel process applied in this study was carried out by chelation of metal ions and citric acid. From the results of thermal gravimetric analysis and XRD analysis of gel powder obtained through sol-gel and heat treatment, gel powders are mostly amorphous, and crystallize completely at $900^{\circ}C$, and the crystalline structure of YAG increases with increasing calcinations temperature. Since YAG prepared by sol-gel & calcinations process was porous, and the sape and size was irregular and nonuniform, the shape and size of YAG powder had to be controlled. Therefore the effects of organic materials such as ethylene glycol and surfactant on the crystalline structure of YAG powder were investigated. Polyesterification of ethylene glycol and citric acid separated reaction area of metal ions in the solution and decreased the size of YAG primary particles. The addition of Igepal 630 as surfactant formed the droplet in the solution, and increased the size of primary particles which forms the aggregate of YAG In order to obtain monodispersed YAG particles of uniform size, gel powder prepared with organic materials had to be milled before calcination. And milling process was very important for obtaining YAG of uniform size.

• Electrical & Electronic Materials
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• v.7 no.2
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• pp.152-156
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• 1994

The rapid thermal annealing effects of Sol-Gel derived ferroelectric PZT thin films were investigated. It was found that rapid thermal annealing(RTA) of spin coated thin films on silicon typically >$800^{\circ}C$ for about 1 min. was changed to the perovskite phase. Rapid thermally annealed films recorded maximum remanent polarization of about 5 .mu.C/cm$^{2}$, coercive field of around 30kV/cm. The switching time for polarization reversal was about 220ns. The films of RTA process showed smooth surface, and high breakdown voltages of over 1 MV/cm and resistivity of $1{\times}{10^12}$ .ohm.cm at 1 MV/cm. It was verified that the polarization reversal of the PZT film was varied partially with applying the multiple short pulse.

• Carbon letters
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• v.10 no.2
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• pp.123-130
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• 2009

Multi-elements doped $TiO_2$ was prepared as a new photocatalyst in order to decrease the band gap of $TiO_2$ by sol-gel process which can provide the large active sites of $TiO_2$. Multi-elements were doped by using a single precursor, tetraethylammonium tetrafluoroborate (TEATFB). By the benefit of large specific surface area of $TiO_2$ prepared by sol-gel process, catalysts showed initial fast removal of dye. The photoactivity showed that the doped catalysts significantly promote the light reactivity than undoped $TiO_2$. The commendable photoactivity of prepared catalysts is predominantly attributable to the doping of anions which may reduce the band gap.