• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.11a
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• pp.59-63
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• 2002

Zinc-Magnesium borosilicate 유리에 CaF$_2$입자를 충진재로 첨가하여 혼합체의 소결거동, 결정화 거동 및 최종 소결체의 마이크로파 유전특성을 측정하였다. CaF$_2$첨가는 유리의 점도를 감소 시켜 결정화 및 수축개시온도를 감소시켰다. 이러한 CaF$_2$의 최대 첨가량은 주어진 유리조성에 있어서 15 vol. % 이었다. 이러한 소결성 및 결정화 개시온도의 변화는 모 유리와 CaF$_2$의 반응에 의한 결과로 보여지며 이 반응은 결정상의 변화나 이차상의 형성에는 영향을 미치지 않았다. 따라서 유전율 6.1에 품질계수가 40000GHz 인 CaF$_2$입자를 15 vol.% 첨가시 유전상수는 7.1에서 5.6로 품질계수는 2200에서 5000GHz로 유전특성이 향상되었고 소결온도는 75$0^{\circ}C$이었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.190-190
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• 2008

자연적으로 발생되는 파도, 비, 우박 등과 철도, 차량 및 엘리베이터 등과 같은 인위적인 설치, 이동에 의해 발생되는 진동에너지는 우리 일상생활에서 가장 흔하게 발생할 수 있는 에너지원인데, 이러한 진동에너지는 압전 소재를 이용하여 재생 가능하여 최근에는 이에 대한 연구가 활발히 진행되어 왔다. 예를 들면, 미국의 MIT에서는 인간이 걸을 때 신발에 가해지는 압력을 이용하여 전력을 발생시키는 연구를 진행하여 2.9 mW의 전력을 얻었다. 특히 이러한 기술은 인간의 걷기 운동 등과 같은 일상적인 동작으로 필요한 전력을 얻을 수 있고, 세라믹 소자를 이용하기 때문에 전자노이즈가 발생되지 않을 뿐 아니라 반영구적으로 사용할 수가 있어서, 소형 전자기기 등에 서 기존 이차전지를 대체 또는 보완 할 수 있는 기술로 검토되고 있다. PZT계 세라믹스는 높은 유전상수와 우수한 압전특성으로 이러한 압전발전 분야에서 가장 널리 사용되어지고 있다. 하지만 에너지 효율을 높이기 위하여 적층 구조의 제작 시 구조적 특성상 내부전극이 도포된 상태에서 동시 소결이 필요한데, $1000^{\circ}C$ 이상의 높은 소결온도 때문에 소재 원가가 낮은 Ag전극 대신 값비싼 Pd나 pt가 다량 함유된 Ag/Pd, Ag/Pt 전극이 사용되고 있어 경제성이 떨어지는 단점을 갖게 된다. 순수 Ag 전극을 사용하거나 Ag의 비율이 높은 내부전극을 사용하기 위해서는 $900^{\circ}C$ 이하에서 소결되고 우수한 전기적 특성을 보이는 압전 세라믹스 소재를 개발 하는 것이 필요하다. 따라서 본 연구에서는 압전특성이 우수한 $(Pb_{1-x}Cd_x)(Ni_{1/3}Nb_{2/3})_{0.25}(Zr_{0.35}/Ti_{0.4})O_3$ 계의 조성을 설계하고, 소결온도를 낮추기 위해서 2 단계 하소법을 이용하였다. 또한 $MnCO_3$, $SiO_2$, $Pb_3O_4$ 등을 소랑 첨가하여 액상 소걸 특성을 부여하여 소결 온도를 감소시키려는 시도도 하였다. 소결체의 전체적인 제조 공정은 일반적인 벌크 세라믹의 소걸 공정을 따랐다. 최종 소결된 시편을 XRD분석을 통하여 상을 확인하였고 SEM을 이용하여 미세조직을 관찰 하였다. 전기적 특성을 평가하기 위하여 두께를 1mm로 연마한 시편에 Ag 전극을 도포하여 $650^{\circ}C$ 에서 열처리한 후, 분극처리 하였다. Impedance analyzer를 이용하여 압전 특성 (전기기계결합계수 및 기계적품질계수)을 측정 하였고, 압전전하상수는 $d_{33}$-meter로 측정하였다. 본 연구에서는 압전체에 가해지는 하중의 크기, 시편의 크기, 하중을 가하는 방법, 에너지 저장회로의 최적화 등을 다양하게 시도하면서 에너지 변환 및 저장 효율을 평가하였다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.667-672
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• 1998

Pyroelectric properties of $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ ceramics prepared by the columbite precursor method have been investigated as a function of the sintering temperature in the range of $1000^{\circ}C$ to $1250^{\circ}C$. The $Pb(Mg_{1/3}Nb_{2/3})O_3-PbTiO_3$ ceramics show typical relaxor ferroelectric behavior. The optimum condition for obtaining samples with high densities and improved pyroelectric properties occur at a sintering temperature of $1250^{\circ}C$ and sintering times of 2 hours. The $Pb(Mg_{1/3}Nb_{2/3}O_3-PbTiO_3$ ceramics show the possibility for pyroelectric sensors with pyrostat.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.1
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• pp.1-5
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• 2019

The physical properties of ceramic materials including oxides are greatly influenced by the material density. Therefore, various efforts have been made to increase the material density. One of the most popular strategies is to use sintering additives in sintering materials. The conventional sintering additive was a spherical powder having a three-dimensional structure. In this study, sintering additive with 2-dimensional (2D) layer structure was used to increase the sintering density of cerium oxide and its effect was confirmed. In this study, 1 nm-thick $TiO_x$ and $MnO_x$ nanosheets were used as sintering additives.

• Journal of the Korean Ceramic Society
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• v.42 no.3 s.274
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• pp.155-164
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• 2005

The characteristics of sintering for Mullite-Cordierite (MC) composites and the effect of $TiO_2$ addition were studied. The MC composites were manufactured by a solution-polymerization method using PVA as a polymer carrier, and $TiO_2$ was used as a sintering agent. They were calcined at $1300^{\circ}C$, planetary milled for 4 h and sintered at $1450^{\circ}C$. As cordierite content increased, relative density of materials was increased up to $98\%$ and sinterability was improved. In case of $50\;wt\%$ mullite/$5\;wt\%$ cordierite composition sintered for 16 h, the flexural strength and thermal expansion coefficient were 190 MPa and $3.07{\times}0^{-6}/^{\circ}C$, respectively. However, mechanical properties were decreased with the cordierite contents higher than $50\;wt\%$ because of the excess liquid-phase amount. As the addition of $TiO_2$ is increased, columnar crystal of mullite and liquid-phase contents were increased. In particular, the flexural strength and thermal expansion coefficient decreased in case of $5\;wt\%\;TiO_2$ addition.

• Journal of the Korean Ceramic Society
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• v.38 no.10
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• pp.914-920
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• 2001

The grain orientation distribution and grain boundary characterization of $ZrB_2$-ZrC composites sintered by a SPS(Spark Plasma Sintering) method, a new sintering technique were analyzed by the EBSP technique and then their crystallographic results have been compared with those of a sintered specimen using a PLS(Pressureless Sintering) method. In the $ZrB_2$-ZrC composite manufactured by SPS, (0001) planes of $ZrB_2$ were oriented in the direction normal to the specimen surface. In the case of PLS, those of $ZrB_2$ were oriented normal to the electron beam. In both cases of PLS and SPS, ZrC grains had the randomly oriented grain structure. The grain boundary characterization showed that low angle grain boundaries in the PLS and SPS processed materials constituted about 10% and 8% of the total number of boundaries, respectively, represented the only slight difference between the proportion of low angle grain boundary. However, in the distribution of CSL(Coincident Site Lattice) boundaries, it was shown the higher proportion of CSL boundaries with $\Sigma$ 3,5,7,9, 11 in the SPS processed material.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.797-803
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• 2004

The heat generation tests of SiC and MO$_2$ samples by use of a microwave heating system were carried out and UO$_2$+5 wt% CeO$_2$ pellets were sintered in a microwave furnace in an oxidizing atmosphere, by taking into account the characteristics of the microwave heating obtained from the heat generation tests. The characteristics of pellets sintered in a microwave furnace were analysed and compared with those of the pellets sintered in a conventional electrical furnace. The temperature of MO$_2$ pellets with microwave heating increased quickly with input power and the variation of output power depended on the reaction characteristics of SiC and MO$_2$ with microwave. The sintered density of UO$_2$+5wt% CeO$_2$ pellets sintered in the microwave furnace was lower about 2% T.D. than that of the pellets sintered in an electrical furnace with sintering parameters. The microstructure of pellets sintered in microwave furnace has a broader pore distribution but has a larger grain size than that of the pellets sintered in the electrical furnace.

• Proceedings of the Korean Ceranic Society Conference
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• 2002.10a
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• pp.121.1-121
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• 2002

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.372-378
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• 2019

Traditional ceramic glazes formulated with copper oxide (CuO) exhibited antibacterial properties on Staphylococcus aureus (Gram Positive) and Escherichia coli (Gram Negative). All the ceramic glazes containing CuO showed antibacterial behavior when fired in reducing atmosphere. However, some of copper glazes presented antibacterial behavior and had no antibacterial properties at all when sintered in an oxidizing atmosphere. To elucidate the antibacterial mechanism, ceramic glazes were studied for phase and microstructure analysis, dissolution behavior and surface zeta potential. Metallic copper was precipitated in the glaze layer when sintered in reducing atmosphere. Less than 0.05 ppm of Cu ion was dissolved from glazes. Ca ion was most dissolved among all the samples. Glaze surface was highly negatively charged when CuO was added over 3 wt.% regardless of the sintering atmosphere. The antibacterial behavior of ceramic glazes seemed to be directly related to the dissolution behavior of cations, but the antibacterial behavior of oxidized specimens was not explained by the dissolution behavior. Surface potential of ceramic glazes appeared to play an auxiliary role in antibacterial properties.

• Journal of the Korean Ceramic Society
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• v.39 no.11
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• pp.1108-1112
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• 2002

pellets were fabricated as a reactor control material by the powder process. Sinterability of $Dy_2O_3+TiO_2$ mixtures and phases of solid solutions were analyzed by using TMA and XRD, respectively. The thermal conductivity of pellet was determined from the measurement data of the specific heat and the thermal diffusivity of the pellet. The sinterability and the sintered density varied as a function of Dy content in $Dy_xTi_yO_z$. The pellet of $3\;g\;Dy/cm^3\;Dy_xTi_yO_z$ melted in the sintering temperature of $1580{\circ}C$. There were two phases of $Dy_2TiO_5+Dy_2Ti_2O_7$ and a single phase of $Dy_2TiO_5$ for the pellet that has the Dy content of and , respectively. The thermal conductivity of $Dy_xTi_yO_z$ was nearly constant in the temperature range of $25~600{\circ}$. It was 1.69~1.78 W/mK for the pellet sintered in and 1.49~1.55 W/mK for the pellet sintered in $1550{\circ}$.