• 한국세라믹학회지
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• 제36권6호
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• pp.671-678
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• 1999

Porous ceramics were fabricated from pressureless powder packing forming method using mullite and cordierite powders granulate by spray drying. The bending strength and shrinkage of porous ceramics were increased and their porosity were decreased with increasing temperature. It showed homogeneous distribution of 2$\mu\textrm{m}$ intergranular pores of mullite at 1400$^{\circ}C$, 2.5$\mu\textrm{m}$ intergranular pores of cordierite at 1300$^{\circ}C$ respedtively. Above that temperature intragranular particles were sintered and sintering by intergranular necking was extremely proceeded. In the test of thermal shock resistance sudden decrease of bending strength to $\Delta$T was not shown because intergranular large pore prevented sudden crack propagation.

• 한국세라믹학회지
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• 제30권2호
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• pp.93-100
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• 1993

The effects of MgO addition on thermal expansiion coefficient and dielectric constant of mullite were studied. Thermal coefficient and dielectric constant decrease with increasing MgO content and exhibit a minimum value at 1wt% MgO. However, above 3wt% MgO content both values increase. Result of X-ray diffraction analysis how that mullite compositions which include more than 0.1wt% MgO form cordierite. Spinel is also formed as well as cordierite in the composition containing more than 3wt% MgO. The results indicate that addition of MgO affect the thermal expansion coefficient and dielectric constant of mullite substrate because of the formation of new phases; cordierite and spinel. The thermal expansion coefficient and dielectric constant are affected mainly by cordierite and spinel in the regions containing less than more than 3wt% MgO, respectively.

• 한국세라믹학회지
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• 제24권5호
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• pp.411-416
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• 1987

Thermal expansions and thermal expansion coefficients of cordierite ceramics reinforced by SiC whiskers up to 40 vol. % were investigated. The composite specimens were hot pressed at 1523K for 30 min under 28.5 MPa pressing pressure in Ar atmosphere. Thermal expansions of the hot pressed composites were measured using a differential dilatometer up to 1262 K in air. Thermal expansions and thermal expansion coefficient of the composites increased with SiC whisker content. Thermal expansion behaviors of the composites were well explained by modelling parallel slabs randomly distributed on the whisker plane as the microstructural element of the composites.

• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 추계총회 및 연구발표회 초록집
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• pp.49.1-49
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• 2003

• 한국세라믹학회지
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• 제56권6호
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• pp.526-533
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• 2019

Indialite/cordierite glass-ceramics demonstrate excellent microwave dielectric properties such as a low dielectric constant of 4.7 and an extremely high quality factor Qf of more than 200 × 10³ GHz when crystallized at 1300℃/20 h, which are essential criteria for application to 5G/6G mobile communication systems. The glass-ceramics applied to dielectric resonators, low-temperature co-fired ceramic (LTCC) substrates, and direct casting glass substrates are reviewed in this paper. The glass-ceramics are fabricated by the crystallization of glass with cordierite composition melted at 1550℃. The dielectric resonators are composed of crystallized glass pellets made from glass rods cast in a graphite mold. The LTCC substrates are made from indialite glass-ceramic powder crystallized at a low temperature of 1000℃/1 h, and the direct casting glass-ceramic substrates are composed of crystallized glass plates cast on a graphite plate. All these materials exhibit excellent microwave dielectric properties.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.280-281
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• 2006

Cordierite 결정상을 LTCC공정 적용온도에서 소결하기 위한 glass 조성을 조사하였다. 상용의 glass중 Pb-B-Si-O계, Na-Zn-B-O계 glass를 선택하였고 LTCC용 기판소재로서의 가능성을 확인하기 위하여 저온 동시소성이 가능한 소결온도인 $850^{\circ}C$와 $1000^{\circ}C$ 사이에서 소재의 소결실험을 진행하였다. 소결조건에 따른 상변화, 유전특성을 확인한 결과 glass상, 결정상, 용융에 의한 glass상으로 상의 변화가 있음을 확인 할 수 있었으며, LTCC 소결 조건에서 Pb-B-Si-O계 glass의 경우 2.9~3.7의 낮은 유전율과 0.0027의 우수한 dielectric loss, 내전압 특성을 가지고 있음을 확인하였다.

• 한국결정성장학회지
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• 제15권5호
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• pp.202-207
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• 2005

Kaolin과 규석 및 $Mg(OH)_2$등의 원료로 만들어진 slip을 casting 할 때 slip의 점도가 slip casting 속도와 소결체의 미세조직에 미치는 영향을 보면 slip-casting속도는 slip의 점도가 낮을 경우 감소하였으며 slip의 점도범위는 $3.0\~17.0\;cP$가 적당하였다. Slip의 점도를 조절하면 표면층, 표면 내부층, 중간층, 내면층의 미세조직을 비교적 균일하게 casting 할 수 있다 소성온도 $1350^{\circ}C$에서 시편의 구성광물은 cordierite 결정만으로 되어있었다.

• 한국전기전자재료학회논문지
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• 제34권5호
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• pp.337-341
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• 2021

Phase evolution, thermal and microwave dielectric properties of cordierite-Al₂O₃ composite were investigated. As the content of Al₂O₃ increased, mullite, sapphirine, and spinel were formed as secondary phases, implying that cordierite may be decomposed by the reaction with Al₂O₃. All sintered specimens exhibited dense microstructures. The densification occurred through liquid phase sintering. As the content of Al₂O₃ increased, the thermal expansion coefficient and the dielectric constant increased, whereas the quality factor decreased. The thermal expansion coefficient, the dielectric constant, and the quality factor of the 90 wt% cordierite 10 wt% Al₂O₃ composite sintered at 1,425℃ were 2.9×10^-6 K^-1, 5.1, and 34,844 GHz, respectively.

• 마이크로전자및패키징학회지
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• 제2권1호
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• pp.49-58
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• 1995

출발물질은 cordierite 유리와 borosilicate/Si3N4 복합분말을 사용하였다. Cordierite 유리조성은 무게비로 17.8MgO-23.1Al2O3-48.1ASiO2-5.0ZnO-1.0B2O3를 선택하였다. Borosilicate/Si3N4복합분말은 sol-gel법으로 a-si3N4 core 분말에 borosilicate 겔을 코팅하여 얻었다. 복합분말과 cordierite 유리 분말을 부피비로 0/100, 12.5/87.5 및 25/75의 조성으로 혼합하여 tape casting 에 의해 green sheet를 제작하였다. 이들 sheet들을 800~100$0^{\circ}C$에서 2시간 소성하여 얻은 시편을 SEM, XRD, 밀도, 유전상수 등을 측정하여 저 유전율의 저온 소성 기판재료를 제조하기 위한 조건들을 검토하였다.

• 한국세라믹학회지
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• 제30권10호
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• pp.845-851
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• 1993

Low firing temperature substrate were synthesized through tape casting and sintering of glass with cordierite composition and then their properties were investigated. Even though the dielectric properties and XRD patterns of substrates, obtained by tape casting and sintering at 900~100$0^{\circ}C$ for various periods, were similar to those of substrates obtained by dry pressing, the sinterability was enhanced. The substrates were thin and the size was 0.6$\times$50$\times$50mm. From the results of dielectric properties, the sinterability and X-ray diffraction pattern, the proper condition for cofiring process with conductor, Cu, was 90$0^{\circ}C$ for 1h. The properties of the substrate are as follows; the dielectric constant was 5.31(at 1MHz), the dissipation factor was 0.0028, the apparent porosity was 0.28% and the main crystalline phase was $\alpha$-cordierite.