• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전기물성,응용부문
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• pp.20-21
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• 2006

In this study, structural and microwave dielectric properties of the ${Ba_5}{B_4}{O_{15}}$ (B=Ta, Nb} cation-deficient perovskite ceramics with sintering temperature were investigated. All sample of the ${Ba_5}{B_4}{O_{15}}$ (B=Ta, Nb) ceramics prepared by conventional mixed oxide method and sintered at $1325^{\circ}C{\sim}1575^{\circ}C$. The bulk density and dielectric constant of the ${Ba_5}{Ta_4}{O_{15}}$ ceramics were increased continuously with increasing of sintering temperature. And the bulk density and dielectric constant of the ${Ba_5}{Nb_4}{O_{15}}$ ceramics was increased in $1375^{\circ}C{\sim}1400^{\circ}C$ but decerased in $1425^{\circ}C$. In the case of ${Ba_5}{Ta_4}{O_{15}}$ ceramics sintered at $1475^{\circ}C$ and ${Ba_5}{Nb_4}{O_{15}}$ ceramics sintered at $1400^{\circ}C$, The dielectric constant and quality factor, and temperature coefficient of the resonant frequency (TCRF) were 25.15, 53,105 GHz, $-3.06\;ppm/^{\circ}C$ and, 39.55, 28,052 GHz, $5.7\;ppm/^{\circ}C$ respectively.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.33.1-33.1
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• 2009

Lead-free (1-x)$(Na_{0.5}K_{0.5})NbO_3$-xBa($Ti_{0.9}Sn_{0.1})O_3$ [NKN-BTS-100x] ceramics doped with 1 mol% $MnO_2$ have been prepared by the conventional solid state method and their structural and piezoelectric properties were investigated. The NKN-BTS-100x ceramics exhibited a dense and homogeneous microstructure when they were sintered at $1030-1150^{\circ}C$. Grain growth was observed for the specimen sintered at relatively low temperature of $1050^{\circ}C$. A tetragonal/orthorhombic morphotropic phase boundary (MPB) in the perovskite structure was also appeared for the NKN-BTS-100x ceramics (0.04$1050^{\circ}C$. The enhanced piezoelectric properties in the NKN-BTS ceramics with a MPB composition were obtained. Especially, for the NKN-BTS-6 ceramics, a high dielectric constant (${\varepsilon}^T_3/\varepsilon_0=1,400$), piezoelectric constant ($d_{33}=237$) and electromechanical coupling factor ($k_p=0.42$) were obtained.

• 한국세라믹학회지
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• 제41권1호
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• pp.41-44
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• 2004

층상구조를 갖는 점토광물은 층상의 이온교환자리에 친소수성 유기물을 화학적으로 치환할 수 있어 도자기 소지의 친소수성 정도를 조절할 수 있다. 본 연구에서는 Montmorillonite를 이온교환법으로 dodecylamine, hexadecylamine과 반응시켜 유기물이 점토광물에 복합화된 유기-점토 복합체를 조조하였다. 유기물이 점토광물 구조에 치환된 위치 및 층상구조의 간격변화는 FT-IR과 WAXD로, 수식된 유기물의 양은 TG-DSC, C/S 기기를 사용하여 조사하였다. 분석을 통하여 유기물은 층상에 선택적으로 치환하여 층간격을 증가 (12${\AA}{\leftrightarro}16{\AA}$) 시키는 역할을 하였고, 비교적 친수성을 보이는 MMT가 첨가된 가소제로 인하여 소수성으로 변하고 있음을 발견하였다.

• 한국결정학회지
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• 제11권4호
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• pp.195-199
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• 2000

Ceramics based on CaTiO₃-NdAlO₃ solid solutions were synthesized in order to study their dielectric microwave properties. Microstructural analysis was performed with scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using different analytical methods such as energy-dispersive X-ray spectroscopy (EDXS). It was observed that the heating conditions during sintering and cooling strongly affect the microstructural development of CaTiO₃-NdAlO₃-based ceramics. Various types and concentrations of structural defects were identified, for example, dislocations, twins and/or antiphase boundaries. all such defects resulted in a degradation of the dielectric microwave properties, in particular the quality factor Q. Dielectric properties of CaTiO₃-NdAlO₃-based ceramics can be improved by an appropriate thermal treatment of ceramics which results in a decrease in the concentrations of the identified microstructural defects.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1411-1413
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• 2001

The $(Ba_{0.5}Sr_{0.5})(Nb_{0.5}Ti_{0.5})O_3$ [BSNT] ceramics were prepared by conventional mixed oxide method. The structural properties of the BSNT ceramics with sintering temperature were investigated by XRD, SEM, EDS. Increasing the sintering temperature, diffraction intensity of the BST(110) peak was increased. The average grain size of BSNT ceramics were increased with sintering temperature. In the case of BSNT ceramics sintered at 1550$^{\circ}C$, the grain was uniform and the pore was not existed. Increasing the sintering temperature from 1400$^{\circ}C$ to 1500$^{\circ}C$, the amount of Nb and Sr were decreased. The density of BSNT ceramics sintered at 1550$^{\circ}C$ was $1.125g/cm^2$.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.426-429
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• 2001

The $BaTiO_{3}+xNb_{2}O_{5}$[x=6, 8, 10wt%] ceramics were prepared by conventional mixed oxide method. The structural properties of the $BaTiO_{3}+xNb_{2}O_{5}$ ceramics with the sintering temperature and addition of $Nb_{2}O_{5}$ were investigated by XRD and SEM. Increasing the sintering temperature, the $2{\Theta}$ value of BT (110) peak was shifted to the lower degree and intensity of the BN (310) peak was increased. Increasing the addition of $Nb_{2}O_{5}$, the intensity of BN (100) peak was decreased and BN (310), (110) peaks were increased. The grain size of the $BaTiO_{3}+xNb_{2}O_{5}$ ceramics sintered at $1350^{\circ}C$ were almost uniform. In the $BaTiO_{3}+xNb_{2}O_{5}$ ceramics sintered at $1350^{\circ}C$, the dielectric constant and dielectric loss were 5424, 0.02 respectively.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 하계학술대회 논문집
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• pp.383-386
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• 2000

The 0.6Ba(Zn$_{1}$3/Ta$_{2}$3/)O$_3$-0.4Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$ceramics were prepared by the conventional mixed oxide method. The structural properties of the 0.6BZT-0.4BCN ceramics with the sintering temperature were investigated by XRD, SEM. The 0.6BZT-0.4BCN ceramics had a complex-perovskite structure. Increasing the sintering temperature, the peak intensity of the superstructure reflection plane were increased and the density and ordering were increased. The density of the 0.6BZT-0.4BCN ceramics sintered at 1475$^{\circ}C$ was 6.455[g/cm$^3$].

• The Korean Journal of Ceramics
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• 제3권2호
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• pp.101-104
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• 1997

Although tribological behavior of Si incorporated DLC films have been intensely investigated, their mechanical properties were not consistent among previous publications. The present work reported the structural change by adding Si, and their effects on the mechanical properties. Si incoporated DLC films were deposited using mixtures of benzene and diluted silane with hydrogen of various volume fractions. We could obtain the films of $X_{si}$ (defined by the Si fraction without considering hydrogen) ranging from 0.01 to 0.21, and found that the mechanical properties of the films changed significantly in the range less than $X_{si}=0.06$. In this range, the hardness and stress increased with Xsi. For higher content of Si, the hardness and stress showed saturated behavior with $X_{si}$. This behavior was discussed in terms of the changes in atomic bond structures.

• 한국결정학회지
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• 제12권2호
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• pp.81-87
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• 2001

We have studied the effect of sintering temperature and time on the cation ordering and second phase formation in Ba(Mg/sub 1/3/Nb/sub 2/3/)O₃(BMN) microwave ceramics by using transmission electron microscopy. The relationship between the structural-chemical behavior arid microwave dielectric properties has also been investigated. It is revealed that according to the sintering conditions the BMN ceramics show very diverse local ordering behavior, such as the development of domain twinning and "core-shell"-structured grains and the formation of local disordered domains, though having 1 : 2 cation ordering structure basically. The disordered structure is found in Mg-excess region. Such local chemical variation seems to be caused by the formation of BaNb₂O/sub 6/-like second phase in its neigh-boring grain boundary. The microwave dielectric quality factor of the ceramics decreases greatly with the increase of the structural-chemical inhomogeneity and diversity.

• 세라미스트
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• 제9권6호
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• pp.30-36
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• 2006

Joining ceramics to metals has a variety of applications both in the structural and the electronics fields. One of the great benefits of the adoption of joining into the structural applications is to provide reliability to the ceramic components by backing up with metal components. In joining ceramics and metals, two key factors, i.e., establishing chemical bonding at interfaces and dissipation of thermal stress across interfaces, should be paid for attention. Many joining methods have been already established such as adhesive and mechanical joining, brazing and soldering, and solid state bonding. Each has its own benefits with some drawbacks. One can select a suitable process and materials following the requirements of the application. This report focuses on the current status of joining technology for ceramics/metal system.