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PbO가 Sol-Gel Process로 제조된 순수 PbTiO3 세라믹스의 소결에 미치는 영향
김선욱,윤만순,김남흥 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.5
Undoped PbTiO3 ceramics was successfully prepared by using sol-gel process, which had not been fabricated due to its microcracks created by anisotropic stress during phase transition from cubic to tetragonal phase. Fabrication of undoped PbTiO3 ceramics via sol-gel processing was very much affected by the PbO content of the samples as well as PbO vapor from sintering atmosphere. Excess PbO was found to promote rapid grain growth in PbTiO3 ceramics. After sintering at 1100$^{\circ}C$ average grain size of PbTiO3 ceramics with excess PbO was about 8 times greater than that of stoichiometric composition, which may be due to PbO liquid phase from excess PbO.
Sol-Gel Processing에 의한 순수 $PbTiO_3$ Ceramics 제조
김선욱,윤만순,임종인,김성숭,김남흥 한국세라믹학회 1992 한국세라믹학회지 Vol.29 No.3
Crack free PbTiO3 ceramics were produced by sol-gel processing using alkoxide, which has not been reported to be successful. The PbTiO3 gels were prepared from Ti alkoxide and lead acetate without any dopants. They were calcined at $600^{\circ}C$ and miled to produce fine PbTiO3 powder. It was pressed into discs and they were sintered at 110$0^{\circ}C$ for a few hours. The sintered ceramics were relativley hard and dense as having about 96% of theoretical density of PbTiO3. Fabrication of pure PbTiO3 ceramics by sol-gel processing is possibly due to their small grain size and uniform distribution of residual stress created during cubic-tetragonal transition over large number of small grains in fine grain PbTiO3 ceramics.
Diplexer 구조를 이용한 Dual Band 방향성 커플러
김기중,박자영,정영학,배효근,김남흥,김학선,Kim Ki-Joong,Park Ja-Young,Jeong Young-Hak,Bae Hyo-Gun,Kim Nam-Heung,Kim Hak-Sun 한국전자파학회 2005 한국전자파학회논문지 Vol.16 No.8
본 논문은 glass 기판 위에 RE IPD(Integrated Passive Device) 기술을 이용하여 dual band 방향성 커플러의 새로운 설계와 구현을 하였으며, 이러한 구조는 전력 증폭기의 출력부에 closed loop 전력 제 어용 GSM/GPRS cellular phones에 적용할 수 있다. 커플러는 방향성 향상을 위하여 보상 capacitor를 이용하였으며, 상호 밴드의 간섭을 최소화하기 위하여 새로운 방법의 필터링 구조(diplexer)를 갖는 커플러를 구현하였다. In this paper, a novel design and implementation of a dual-band directional coupler based on RF IPD(Integrated Passive Device)-on-glass technology is proposed, which can be adopted in GSM/GPRS cellular phones for closed loop power control at the output of the power amplifier. The proposed coupler has a compensation capacitor to improve the directivity, and was designed using a new diplexing structure to minimize the cross-band isolation.