• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.315-318
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• 2001

The optical and dielectric properties of TiO$_2$ thin films prepared with mixtures of Epoxy, bits-(4, 4'-p-toluenesulfonylacidic isoproplylidene)-cyclohexadiol and UVI 6990 in dry sol-gel process were investigated. The absorption peak of the films was showed at 360nm. Photocurrent of the thin films doped with 50 wt% of TiO$_2$was higher than that of nondoped thin films. Energy gap was lowered from 3.6 to 3.3 eV with increasing amount of TiO$_2$. Relative dielectric constants of samples were 1.5 to 3 and showed a characteristics of lower dielectric materials.

• 한국세라믹학회지
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• 제34권11호
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• pp.1187-1197
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• 1997

Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt% $\alpha$-Al2O3, and ball milled gel were 1192$^{\circ}C$, 1184$^{\circ}C$, 1141$^{\circ}C$, 1119$^{\circ}C$, 1117$^{\circ}C$, and 1106$^{\circ}C$, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt% $\alpha$-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt% $\alpha$-Al2O3 was 96% when sintered at 140$0^{\circ}C$ for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130$0^{\circ}C$ for 1h. The size and amount of $\alpha$-Al2O3 particles added by ball milling were 0.107 ${\mu}{\textrm}{m}$ and 0.5 wt%.

• 한국세라믹학회지
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• 제30권7호
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• pp.535-542
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• 1993

It was investigated in this study that a preparation method, activation energy, surface area, pore volume, pore size distribution and DTA analysis of the dry gel in process of producing monolithic porous gel in Li2O-Al2O3-TiO2-SiO2 system by the sol-gel technique using metal alkoxides. Activation energy for gellation according to the variation of water concentration and the kind of catalysts ranged from 10 to 20kcal/mole. Monolithic dry gels were prepared after drying at 9$0^{\circ}C$ when the amount of water for gellation was 4~8 times more than the stoichiometric amount, that was necessary for the full hydrolysis of the mixed metal alkoxide. The specific surface area, the pore volume, the average pore radius of the dried gel at 18$0^{\circ}C$ according to the various kinds of catalyst were about 348~734$m^2$/g, 0.35~0.70ml/g and 10~35$\AA$, respectively. It showed that the dry gels were porous body. As a result ofthe analysis of DTA, it was confirmed that the exothermaic peaks at 715$^{\circ}C$ and 77$0^{\circ}C$ was clue to the crystallization of dried gel.

• 한국세라믹학회지
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• 제40권2호
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• pp.153-158
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• 2003

Photosensitive sol solution을 이용한 self pattern된 박막은 photoresist/dry etching process에 비해 박막의 제조과정이 간단하다는 장점을 가지고 있다. 이 연구에서는 강유전성 메모리소자의 산화물 전극재료로 사용되고 있는 La$_{0.5}$Sr$_{0.5}$CoO$_3$(LSCO)극 photosensitive sol solution을 이용하여 spin coating법으로 제조하였으며 출발원료는 La-2methoxyethoxide, Sr-ethoxide, Co-2methoxyethoxide를 사용하였다. LSCO gel 박막에 UV 노광시간을 증가시킴에 따라 M(metal)-O-M 결합이 생성되면서 metal $\beta$-diketonate의 UV 흡수 피크 강도는 감소되었고 LSCO gel 박막에 UV조사에 따른 용해도 차이가 생기면서 fine patterning 을 얻을 수 있었다. 68$0^{\circ}C$ 이상의 온도로 대기 중에서 열처리된 LSCO 박막은 perovskite 상을 나타내었고 74$0^{\circ}C$에서 가장 낮은 비저항값(4$\times$10￣$^3$Ωcm)을 얻을 수 있었다.

• 한국세라믹학회지
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• 제32권4호
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• pp.507-515
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• 1995

The monolithic dry gels of the Li2O-Al2O3-TiO2-SiO2 system were prepared by the sol-gel technique using metal alkoxides as starting materials to obtain monolithic glass-ceramics at low temperature without melting. Activation energy for the crystal growth of the gel with 6.05% TiO2, nucleating ageng, for the preparation of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was 101.14kcal/mol. As a result of the analysis of DTA & XRD, it was confirmed that the crytallization of Li2O-Al2O3-TiO2-SiO2 system glass-ceramic was the most efficient when 6.05% TiO2, nucleating agent, was added. $\beta$-eucryptite solid solution crystals and $\beta$-spodumene solid solution crystals were detected in the sample heat treated above 85$0^{\circ}C$. The sintered gel heat treated at 85$0^{\circ}C$ had the specific surface area of 185$m^2$/g, the pore volume of 0.19cc/g and the average pore radius of 20.8$\AA$. This shows that the sintered gel is also comparatively porous material. In temperature range of 25~85$0^{\circ}C$ thermal expansion coefficient of the specimen which was crystallized for 10hrs at 85$0^{\circ}C$ was 6.7$\times$10-7/$^{\circ}C$, which indicated that the crystallized specimen was turned out to be the glass-ceramic with low thermal expansion.

• 한국세라믹학회지
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• 제35권1호
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• pp.66-78
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• 1998

the microstructure and mechanical properties of seeded and ball-milled dry gels prepared by boehmite sol-gel method were discussed. The densification of seeded gels was improved with increasing seed content namely the number of seed The number of seed was 1.09, 3.35, 5.72${\times}$1012/cm3 boehmite when seeded with 1, 3, 5wt% respectively The ball milled gel contained about 0.5wt% seed and the number of seed was 4.72${\times}$1012/cm3 boehmite. The sintered density of 5wt% seeded gel was below 80% when sintered at 1300$^{\circ}C$ for 1h. On the other hand that of ball milled gel was very improved and reached to 97% In the case of 3wt% seeded gels the density over 97% was attained when sintered at 1500$^{\circ}C$for 1h. and the grain of the sintered body was several micrometers in size. However the sintered body of ball milled gel showed grain size of submicrometer when sintered at 1300$^{\circ}C$ for 1h. And this specimen showed highest harness value of 1900kg/mm2 The fracture toughness increased with increasing sintering temperature. The sintered body of ball milled gel showed the largest grain size and the highest fracture toughness without regard to sint-ering temperature.

• 한국세라믹학회지
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• 제39권8호
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• pp.750-757
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• 2002

Photosensitive sol solution을 이용한 self pattern된 박막은 photoresist/dry etching process에 비해 박막의 제조과정이 간단하다는 장점을 가지고 있다. 이 연구에서는 photosensitive sol solution을 이용하여 spin coating법에 의해 $Sr_{0.9}Bi_{2.1}Ta_2O_9$의 조성을 갖는 강유전체 박막을 제조하였으며 출발원료는 $Sr(OC_2H_5)_2,\;Bi(TMHD)_3$와 $Ta(OC_2H_5)_5$를 사용하였다. SBT 박막에 UV 노광시간을 증가시킴에 따라 M-O-M 결합이 생성되면서 metal ${\beta}$-diketonate의 UV 흡수 피크 강도는 감소되었고 SBT 박막에 UV 조사에 따른 용해도 차이가 생기면서 fine patterning을 얻을 수 있었다. 또한 UV가 조사된 SBT 박막의 강유전 특성이 UV가 조사되지 않은 것보다 우수하였다.

• 한국세라믹학회지
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• 제30권3호
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• pp.169-174
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• 1993

The porous silica glass prepared by the sol-gel method from the mixed solution of Si(OCH3)4, H2O, HCl and CH3OH with HCONH2 as a DCCA (Drying Control Chemical Additives). For investigation the characteristics of gels and glasses, we examined gels and glasses using TG-DTA, XRD, IR, SEM and porosimeter. The more content of formamide in the mixed solution increased, the more pore size and porosity of gel increased. In the excess formamide added gel, the properties of pore of gel were not so changed. The porous silica glass was prepared from the dry gel after heat treatment at 75$0^{\circ}C$. Porosity and mean pore size of the porous silica glass was 17~25% and 40~60$\AA$ relatively.

• Transactions on Electrical and Electronic Materials
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• 제3권1호
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• pp.42-45
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• 2002

Properties of lead zirconate titanate ferroelectric thin films prepared by rapid thermal annealing/direct insertion thermal annealing were investigated. The remnant polarization (Pr), saturation polarization (Ps), and coercive force (Ec) of typical samples annealed by rapid thermal annealing (RTA) are about 13.7 $\mu$ C/cm$^2$, 27.1 $\mu$C/cm$^2$, and 55.6 kV/cm, respectively. The dielectric constant of the sample is about 786, the dielectric loss tangent is about 2.4% at 1 kHz. Furthermore, ferroelectric, conduction, and piezoelectric properties of the thin films annealed by RTA process and the direct insertion thermal annealing (DITA) process were compared. The influence of temperature in the dry process on the above properties was also investigated.

• 한국세라믹학회지
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• 제38권9호
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• pp.794-798
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• 2001

Sol-gel법에 의하여 $Y_{2-x}SiO_5:Ce_x^{3+}$ (x=0.002∼0.04) 형광체를 제조하고 발광특성을 평가하였다. 800$^{\circ}$C에서 하소하였을 때는 무정형의 결정상이 나타났지만 1000$^{\circ}$C 이상에서는 $X_2$ type의 $Y_2SiO_5$ 결정상을 얻었다. 230∼360nm에서 형광체 모체의 광흡수가 일어났으며 300∼400nm에서 Ce 첨가로 인한 형광체의 광흡수가 관찰되었다. 436nm에서 최대의 발광 spectrum을 나타내었으며 $Ce^{3+}$ 함량을 0.025mol 첨가 시 $Y_{2-x}SiO_5:Ce_x^{3+}$ 형광체는 최대의 cathodoluminescence 특성과 CIE1931색 좌표 상에서 x=0.161, y=0.124의 색을 나타내었다.