• Journal of Powder Materials
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• v.24 no.6
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• pp.437-443
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• 2017

SiC-based composite materials with light weight, high durability, and high-temperature stability have been actively studied for use in aerospace and defense applications. Moreover, environmental barrier coating (EBC) technologies using oxide-based ceramic materials have been studied to prevent chemical deterioration at a high temperature of $1300^{\circ}C$ or higher. In this study, an ytterbium silicate material, which has recently been actively studied as an environmental barrier coating because of its high-temperature chemical stability, is fabricated on a sintered SiC substrate. $Yb_2O_3$ and $SiO_2$ are used as the raw starting materials to form ytterbium disilicate ($Yb_2Si_2O_7$). Suspension plasma spraying is applied as the coating method. The effect of the mixing method on the particle size and distribution, which affect the coating formation behavior, is investigated using a scanning electron microscope (SEM), an energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) analysis. It is found that the originally designed compounds are not effectively formed because of the refinement and vaporization of the raw material particles, i.e., $SiO_2$, and the formation of a porous coating structure. By changing the coating parameters such as the deposition distance, it is found that a denser coating structure can be formed at a closer deposition distance.

• Progress in Superconductivity and Cryogenics
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• v.8 no.3
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• pp.13-17
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• 2006

The effect of the addition of the nano size $Y_2O_3$ powder on the microstructurte and superconducting properties of YBCO thin film deposited on LAO single crystalline substrate by TFA-MOD method was studied. Nano size $Y_2O_3$ powder was added to the stoichiometric precursor solution with a cation ratio of Y : Ba . Cu = 1 : 2 : 3 prepared using TFA as chelating agent. Precursor solutions with and without $Y_2O_3$ addition were coated on $LaAlO_3(100)$ single crystalline substrates by dip coating method. Calcination and conversion heat treatments were performed in controlled atmosphere containing moisture Current carrying capacity(Jc) of YBCO film was enhanced about 50% by $Y_2O_3$ doping and it is thought to be due to the better connectivity of YBCO grains and/or the flux pinning by the $Y_2O_3$ particles embedded in YBCO grains.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.5
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• pp.254-259
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• 2003

In the fabrication process of transparent conducting thin films of the ATO (antimony-doped tin oxide) on a soda lime glass substrate by a sol-gel dip coating method, the effects of the $SiO_2$ buffer layer formed on the substrate and $N_2$ annealing treatment were investigated by XPS (X-ray photoelectron spectroscopy) analysis. Optical transmittance and electrical resistivity of the 400 nm-thick ATO thin films which were deposited on $SiO_2$ buffer layer/soda lime glass and then annealed under nitrogen atmosphere were 84 % and $5.0\times 10^{-3}\Omega \textrm{cm}$ respectively. The XPS analysis confirmed that a $SiO_2$ buffer layer inhibited Na ion diffusion from the substrate, resulting in prohibiting the formation of a secondary phase such as $Na_2SnO_3$ and SnO and increasing Sb ion concentration and ratio of $Sb^{5+}/Sb^{3+}$ in the film. And it was also found that $N_2$ annealing treatment leads to the reduction of $Sn^{4+}$as well as $Sb^{5+}$ however the reduction of $Sn^{4+}$ is more effective and therefore consequently results in decrease in the electrical resistivity to produce an excellent electrical properties of the film.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.516-524
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• 1995

In this study, to prepare the dielectric (Ba, Sr)TiO3 thin films by the sol-gel process, Titaminum (IV) sio-propoxide (Ti[OCH(CH3)2]4), Ba and Sr acetate were used for sol and thin films were prepared by dip-coating process. Stability of sol decreased with the increase of Sr, and thickness of thin films were obtained 0.13~0.17${\mu}{\textrm}{m}$ by 1 coating cycle. Transmittance of amorphous thin films heated at 500 and 55$0^{\circ}C$ was very good, and crystallization tendency of thin films according to heat-treatment temperature and crystallization characteristics of thin films heated at 11$0^{\circ}C$ for 3 hrs were analysed. As a result, good perovskite structure was obtained higher than 100$0^{\circ}C$, and tetragonality of thin film was decreased but pyrochlore was formed with increasing Sr. In case of addition to substitute 0.4mol% Sr for Ba, dielectric constant was 288 and loss factor (tan $\delta$) was 0.04.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.3
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• pp.248-251
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• 2009

We have investigated the effect of the quality of 1.3 um distributed feed back laser diode (DFB-LD) on the design of anti-reflection (AR) coatings. Optimal condition of AR coating to prevent internal feedback from both facets and reduce the reflection-induced intensity noise of laser diode was simulated with Macleod Simulator. Coating materials used in this work were ${Ti_3}{O_5}$ and $SiO_2$, of which design thickness were 105 nm and 165 nm, respectively. AR coating films were deposited by Ion-Assisted Deposition system. The electrical and optical properties of 1.3 um laser diode were characterized by Bar tester and Chip tester. Threshold current and slop-efficiency of DFB-LD were 27.56 mA 0.302 W/A. Far field pattern and wavelength of DFB-LD were $22.3^{\circ}(Horizontal){\times}24.4^{\circ}$ (Vertical), 1313.8 nm, respectively.

• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.54-60
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• 1985

Gas sensing materials for detecting flammable gases such as $CH_4$, $C_3H_8$ and n-$C_4H_{10}$ were developed by util-izing $In_2O_3$ as the principal sensing material. The sensing materials were formulated by mixing $In_2O_3$ powder with one or two other chemicals such as $SnO_2$, $Y_2O_3$ and $Al_2O_3$ with a small addition of $PdCl_2$ as a catalyst. Sample of sensor were fabricated by coating each of the mixtures on a ceramic tube impregnating ethylsili-cate and firing at 75$0^{\circ}C$ Each material mixture was evaluated by measuring and comparing gas sensitivity(resistance in air/resistance with gas) to flammable gases such as $CH_4$, $C_3H-8$ and n-$C_4H_{10}$. It was found that among fifteen compositions tested three compositions as follows show the highest gas sensitivity and thus are very feasible for commercialization as the gas sensors ; o49.5 $In_2O_3$+50 Al2O3_0.5 PdCl2(wt%) o $20In_2O_3+29$ $SnO_2+50$ $Al_2O_3+1$ $PdCl_2$(wt%) o40 $In_2O_3$+9 $Y_2O_3+50$ $Al_2O_3+1$ $PdCl_2$(wt%)

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.1-5
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• 2008

The effect of $BaCeO_3$ doping on the critical current density of YBCO film by TFA-MOD method was studied. $BaCeO_3$ doping was made by two method; one is direct addition of $BaCeO_3$ nano-sized powder prepared by citrate process followed by grinding with planetary ball mill for 10 hours. Another is addition of Ba-Ce precursor solution prepared with Ba-acetate and Ce acetate dissolved in TFA to the YBCO-TFA precursor solution. The film was made by standard dip coating and heat treatment process with conversion temperature of $790^{\circ}C$ in 1000 ppm oxygen containing moisturized Ar gas atmosphere. The direct addition of $BaCeO_3$ powder resulted in YBCO film with good epitaxial growth and no evidence of second phase formation. The addition through precursor solution resulted in the increase of critical current density upto 30 at% doping and uniform dispersion of $BaCeO_3$ fine inclusion was confirmed by SEM-EDX.

• Journal of the Korean Ceramic Society
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• v.41 no.10 s.269
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• pp.735-741
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• 2004

$LiMn_{1.92}Co_{0.08}O_4$ and $LiNi_{0.7}Co_{0.3}O_2$ synthesized by a simplified combustion method had good electrochemical properties. Mixtures $LiMn_{1.92}Co_{0.08}O_4$-x wt$\%$ $LiNi_{0.7}Co_{0.3}O_2$ (x=9, 23, 33, 41, and 47) were prepared by milling for 30 min and their electrochemical properties were investigated. The electrode with x=9 had a relatively large first discharge capacity (109.9 mAh/g at 0.1 C) and good cycling performance. The decrease in the discharge capacity of the mixture electrodes with cycling is considered to result mainly from the degradation of $LiNi_{0.7}Co_{0.3}O_2$, caused by coating of $LiNi_{0.7}Co_{0.3}O_2$ with Mn dissolved from $LiMn_{1.92}Co_{0.08}O_4$.

• Journal of Surface Science and Engineering
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• v.35 no.3
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• pp.133-140
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• 2002

The Ti-Si-N coating layers were synthesized on SKD 11 steel substrate by a DC reactive magnetron co-sputtering technique with separate Ti and Si targets. The high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS) analyses for the coating layers revealed that microstructure of Ti-Si-N layer was nanocomposite, consisting of nano-sized TiN crystallites surrounded by amorphous $Si_3$$N_4$ phase. The highest hardness value of about 39 GPa was obtained at the Si content of ~11at.%, where the microstructure had fine TiN crystallites (about 5nm in size) dispersed uniformly in amorphous matrix. As the Si content in Ti-Si-N films increased, the TiN crystallites became from aligned to randomly oriented microstructure, finer, and fully penetrated by amorphous phase. Free Si appeared in the layers due to the deficit of nitrogen source at higher Si content. Friction coefficient and wear rate of the Ti-Si-N coating layer significantly decreased with increase of relative humidity. The self-lubricating tribe-layers such as $SiO_2$ or (OH)$Si_2$ seemed to play an important role in the wear behavior of Ti-Si-N film against steel.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
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• 2006.10a
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• pp.170-173
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• 2006

Ferroelectric $Bi_{3.35}Sm_{0.65}Ti_3O_{12}(BST)$ thin films were deposited on $Pt(111)/Ti/SiO_2/Si(100)$ substrates by a sol-gel spin-coating process. In this experiments, $Bi(TMHD)_3$, $Sm_5(O^iPr)_{13}$, $Ti(O^iPr)_4$ were used as precursors, which were dissolved in 2-methoxyethanol. Thereafter, the thin films with the thickness, of 240nm were annealed from 600 to $720^{\circ}C$ in oxygen atmosphere for 1 hr, and post-annealed in oxygen atmosphere for 1 hr after deposition of Pt electrode to enhance the electrical properties. The remanent polarization and coercive voltage of the BST thin films annealed at $720^{\circ}C$ were $19.48\;{\mu}C/cm^2$ and 3.40 V, respectively, and a fatigue-free characteristics. As a result, Sm-substituted bismuth titanate films with good ferroelectric properties and excellent fatigue resistance are useful candidates for ferroelectric memory applications.