• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.48-48
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• 2008

현재 압전재료로써 사용되고 있는 PZT계 세라믹스는 우수한 압전 및 유전특성으로 초음파 센서, 압전변압기, 액츄에이터, 필터, 레조네이터와 같은 여러 응용분야에 널리 사용되어지고 있다. 그러나 납을 60%이상 포함하므로 환경오염에 의하여 그 사용에 대한 규제가 강화되고 있어 최근에는 납을 함유하지 않은 무연 환경친화형 압전세라믹스가 주목받고 있다. 현재 무연 조성 세라믹스에는 텅스텐-브론즈 형, 비스머스 레이어형, 페로브스카이트 형 등이 이으며, 그 중 페로보스카이트 혈을 제외하고는 보통 소성법 조제시 낮은 압전특성을 갖는다. 그러므로 압전특성을 증가시키기 위하여 Hot pressing, Hot forging, RTGG(Reactive Template Grain Growth), SPS(Spark Plasma Sintering), 그러나 이는 무연 세라믹스의 대량생산 과정에서 어려운 문제를 가지고 있고, 저가격 관점에서 볼 때 보통소성법이 보다 바람직하다. 그래서 보통소성법으로 NKN세라믹스의 소결성을 향상 시키고 비교적 높은 압전특성을 얻기 위해서 $LiSbO_3$, $LiNbO_3$, $LiTaO_3$, alkaline-earth(Mg, Ca, Sr, Ba) 등을 첨가한 논문들이 보고되고 있으며, 이러한 재료들의 kp는 대략 0.3-0.4를 나타내고 있다. 따라서, 본 연구에서는 소결온도를 낮추고자 $Ag_2O$를 소결조제로 사용하였고 유전 및 압전특성을 높이고자 소결시간 변화시켜 시편을 제작하여 NKN 세라믹스의 유전 및 압전특성을 조사하였다.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.7-11
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• 2012

Plasma electrolytic oxidation of magnesium alloys is a well known technique to produce corrosion and wear resistant coatings. The addition of particles to the electrolyte provides a possibility to produce coatings with an increasing range of composition by in-situ incorporation of those particles into the coating. An extensive literature review has revealed that the mode of incorporation depends mainly on the melting point of the used particles and the energy provided by the discharges of the PEO process. The spectrum ranges from inert to partly reactive incorporation, but a complete reactive incorporation and a formation of a new single phase coating was not observed so far. Thus a new approach in PEO processing is introduced using specific particles as a kind of sintering additive, changing not only the composition but lowering the melting temperature and increase the liquid phase fraction during the discharges, resulting in a new amorphous coating.

• 한국세라믹학회지
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• 제26권2호
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• pp.221-227
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• 1989

To investigate the development and densification YBa2Cu3O7-x(1-2-3) superconducting phase, the 1-2-3 phase powders have been prepared by citrate and nitrate processes with changing calcination temperature. Nearly pure 1-2-3 phase peaks have been obtained by calcining the precursor in air at 90$0^{\circ}C$ for 2.5h in citrate process but at 95$0^{\circ}C$ for 2.5h in nitrate process. The sintering density of citrate derived sample calcined at 80$0^{\circ}C$ has been about 4% higher than that calcined at 90$0^{\circ}C$, although the compacting density has been lower at 80$0^{\circ}C$ calcination. This can be explained that the 1-2-3 phase particles formed at 80$0^{\circ}C$ have reactive sub-micron size which has good sinterbililty.

• 한국세라믹학회지
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• 제23권3호
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• pp.1-8
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• 1986

The preparation and electrical conductivity of $\beta$-$Al_2O_3$ are investigated as a function of $Na_2O$ content from the-oretical composition of $\beta$-$Al_2O_3$ to that of $\beta$"-$Al_2O_3$. $\beta$-$Al_2O_3$ $\beta$"$Al_2O_3$$\alpha$-Al2O3 and ${\gamma}$-NaAlO2 phases appear in the calcined powder at 125$0^{\circ}C$ for 2 hours. The majoity phase is $\beta$-$Al_2O_3$ in sintered specimens at 155$0^{\circ}C$ and 1$650^{\circ}C$ for 30 mins respectively and ${\gamma}$-4NaAlO_2$ phase also exists when Na2O content is over 10.39w/o ${\gamma}$-4NaAlO_2$ phase does not affect the grain growth of $\beta$-$Al_2O_3$ in sintering at 155$0^{\circ}C$ but acts as a reactive liquid for the abnormal grain growth of $\beta$-$Al_2O_3$in sintering at 1$650^{\circ}C$ The electrical conduction of $\beta$-$Al_2O_3$is predominated by 4Na^+$ ion. Contribution of ionic con-ductivity to total conductivity is gradually decreased with increasing temperature at given oxygen pressure and to -tal conductivity is increased by positive hole due to interstitial oxygen with increasing oxygen pressure.

• 한국재료학회지
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• 제17권7호
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• pp.366-370
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• 2007

Silicon nitride ($Si_3N_4$) ceramics have been considered for various components of nuclear power plants such as the mechanical seal of a reactor coolant pump (RCP), the guide roller for a control rod drive mechanism (CRDM), and a seal support, etc. Corrosion behavior of $Si_3N_4$ ceramics in a high-temperature and high-pressure water must be elucidated before they can be considered as components for nuclear power plants. In this study, the corrosion behaviors of $Si_3N_4$ ceramics containing MgO and $Al_2O_3$ as sintering aids were investigated at a hydrothermal condition ($300^{\circ}C$, 9.0 MPa) in pure water and 35 ppm LiOH solution. The corrosion reactions were controlled by a diffusion of the reactive species and/or products through the corroded layer. The grain-boundary phase was preferentially corroded in pure water whereas the $Si_3N_4$ grain seemed to be corroded at a similar rate to the grain-boundary phase in LiOH solution. Flexural strengths of the $Si_3N_4$ ceramics were significantly degraded due to the corrosion reaction. Results of this study imply that a variation of the sintering aids and/or a control (e.g., crystallization) of the grain-boundary phase are necessary to increase the corrosion resistance of $Si_3N_4$ ceramics in a high-temperature water.

• 센서학회지
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• 제22권2호
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• pp.130-135
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• 2013

This study proposed a noble process to fabricate TSV (Through Silicon Via) structure which has lower cost, shorter production time, and more simple fabrication process than plating method. In order to produce the via holes, the Si wafer was etched by a DRIE (Deep Reactive Ion Etching) process. The via hole was $100{\mu}m$ in diameter and $400{\mu}m$ in depth. A dielectric layer of $SiO_2$ was formed by thermal oxidation on the front side wafer and via hole side wall. An adhesion layer of Ti and a seed layer of Au were deposited. Soldering process was applied to fill the via holes with solder paste and metal powder. When the solder paste was used as via hole metal line, sintering state and electrical properties were excellent. However, electrical connection was poor due to occurrence of many voids. In the case of metal powder, voids were reduced but sintering state and electrical properties were bad. We tried the via hole filling process by using mixing solder paste and metal powder. As a consequence, it was confirmed that mixing rate of solder paste (4) : metal powder (3) was excellent electrical characteristics.

• 한국세라믹학회지
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• 제29권11호
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• pp.900-904
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• 1992

High temperature electrical conductivity was measured for perovskite La0.98Sr0.02MnO3 at 200~130$0^{\circ}C$ as a function of Po2 and 1/T. Perovskite La1-xSrxMnO3 system is the typical oxygen electrode in solid oxide fuel cell (SOFC). Acetate precursors were used for the preparation of mixed water solution and the calcined powders were reacted with Na2CO3 flux in order to obtain highly reactive powders of perovskite La0.98Sr0.02MnO3. The relative density was greatly increased above 90% because of the homogeneous sintering. From the conductivity ($\sigma$)-temperature and conductivity-Po2 at constant temperature, the defect structure of La0.98Sr0.02MnO3 was discussed. From the slope of 1n($\sigma$) vs 1/T, the activation energy of 0.069 and 0.108eV were evaluated for above 40$0^{\circ}C$, respectively. From the relationship between $\sigma$ and Po2, it was found that the decomposition of La0.98Sr0.02MnO3 was occurred at 10-15.5 atm(97$0^{\circ}C$) and 10-11 atm(125$0^{\circ}C$). It is supposed that the improvement of p-type conductivity may be leaded by the increase of Mn4+ concentration through the substitution of divalent/monovalent cations for La site in LaMnO3.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2002년도 춘계 기술심포지움 논문집
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• pp.169-172
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• 2002

This study demonstrated the feasibility of using tape-casting followed by sintering as a low-cost alternative for coating glass-ceramic or glass film on a metal substrate. The process has been successfully used to fabricate a glass-on-stainless steel and a glass-ceramic-on-molybdenum electrostatic chuck(ESC) with the insulating layer thickness about $150{\mu}{\textrm}{m}$. Electrical resistivity data of the coaling were obtained between room temperature and 55$0^{\circ}C$; although the resistivity values dropped rapidly with increasing temperature in both coatings, the glass-ceramic still retained a high value of $10^{10}$ ohm-cm at $500^{\circ}C$. Clamping pressure measurements were done using a mechanical apparatus equipped with a load-cell at temperatures up to $350^{\circ}C$ and applied voltages up to 600V; the clamping behavior of all ESCs generally followed the voltage-squared curve as predicted by theory. Based on these results, we believe that we have a viable technology for manufacturing ESCs for use in reactive-ion etch systems.

• 한국분말재료학회지
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• 제28권6호
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• pp.502-508
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• 2021

SiAlON-based ceramics are a type of oxynitride ceramics, which can be used as cutting tools for heat-resistant super alloys (HRSAs). These ceramics are derived from Si3N4 ceramics. SiAlON can be densified using gas-pressure reactive sintering from mixtures of oxides and nitrides. In this study, we prepare an α-/β-SiAlON ceramic composite with a composition of Yb_0.03Y_0.10Si_10.6Al_1.4O_1.0N_15.0. The structure and mechanical/thermal properties of the densified SiAlON specimen are characterized and compared with those of a commercial SiAlON cutting tool. By observing the crystallographic structures and microstructures, the constituent phases of each SiAlON ceramic, such as α-SiAlON, β-SiAlON, and intergranular phases, are identified. By evaluating the mechanical and thermal properties, the contribution of the constituent phases to these properties is discussed as well.

• 마이크로전자및패키징학회지
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• 제30권4호
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• pp.79-85
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• 2023

(1-4x)Bi_1.5Zn_1.0Nb_1.5O₇-3xBi₂Zn_2/3Nb_4/3O₇-2xLiZnNbO₄(x=0.03-0.21) 조성의 새로운 저온 동시 소성 세라믹(LTCC) 유전체는 Bi_1.5Zn_1.0Nb_1.5O₇-xLi₂CO₃(x=0.03-0.21) 혼합물을 850℃~920℃에서 4 시간 반응성 액상소결(reactive liquid phase sintering)을 하여 제조하였다. 소결이 진행되는 동안 Li₂CO₃는 Bi_1.5Zn_1.0Nb_1.5O₇과 반응하여 Bi₂Zn_2/3Nb_4/3O₇과 LiZnNbO₄를 생성하였고 얻어진 소결체의 상대 소결밀도는 이론 밀도의 96% 이상이었다. 초기 Li₂CO₃ 함량(x)을 조절하여 최종 소결체내에 존재하는 Bi_1.5Zn_1.0Nb_1.5O₇, Bi₂Zn_2/3Nb_4/3O₇ 및 LiZnNbO₄ 상의 상대적인 함량을 제어함으로써 높은 유전율(ε_r), 낮은 유전손실(tan δ) 및 NP0 특성(TCε ≤ ±30 ppm/℃)의 유전율 온도계수(TCε)를 갖는 유전체를 개발할 수 있었다. Li₂CO₃의 첨가가 x=0.03 mol에서 x=0.15 mol로 증가함에 따라 얻어진 복합체 내의 Bi₂Zn_2/3Nb_4/3O₇와 LiZnNbO₄의 부피 분율은 증가하였고, Bi_1.5Zn_1.0Nb_1.5O₇의 부피 분율은 감소하였다. 그 결과 복합체의 유전율(ε_r)은 148.38에서 126.99로 유전손실(tan δ)은 5.29×10^-4에서 3.31×10^-4로 그리고 유전율 온도계수(TCε)는 -340.35 ppm/℃에서 299.67 ppm/℃로 변화되었다. NP0 특성을 갖는 유전체는 Li₂CO₃의 함량이 x=0.09일 때 얻을 수 있었고, 이 때의 유전율(ε_r)은 143.06, 유전손실(tan δ)값은 4.31×10^-4, 그리고 유전율 온도계수(TCε)값은 -9.98 ppm/℃ 이었다. Ag전극과의 화학적 호환성 실험은 개발된 복합 재료는 Ag 전극과 동시 소성 과정에서 전극과 반응이 없음을 보여주었다.