• Proceedings of the Korean Ceranic Society Conference
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• 2004.10a
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• pp.88.3-88.3
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• 2004

• Journal of the Korean Ceramic Society
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• v.38 no.3
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• pp.256-260
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• 2001

본 연구에서는 Sbrk 치환된 BaTiO$_3$에 그라파이트를 첨가하고 고상반응법을 이용하여 PTC 소자를 제조한 후, 저항-온도 특성을 조사하였으며 미세구조 분석을 통하여 그라파이트 첨가로 인한 PTC 특성 변화를 고찰하였다. 시편의 저항-온도 특성은 자체 제작한 저항-온도 특성 자동 측정 시스템을 사용하였으며 미세구조 고찰은 주사 전자 현미경을 사용하였다. 상온 저항값은 그라파이트를 1.5 mol% 첨가한 시편이 8.8Ω.cm로 가장 낮은 저항값을 나타내었고 저항-온도 계수는 그라파이트를 3.0 mol% 첨가한 시편이 22.4%/$^{\circ}C$로 가장 좋은 PTC 효과를 보였다. 미세구조 고찰 결과 그라파이트를 1.5 mol% 첨가한 경우 90$^{\circ}$ 및 180$^{\circ}$전계구조가 상당히 발달되었음을 볼수 있었다.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1504-1506
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• 2002

$(Ba_{0.6-x}-Sr_{0.4}Ca_x)TiO_3$ (x=0.10, 0.15, 0.20, y=$0.0{\sim}3.0$) powders were fabricated by the sol-gel method, and BSCT thick films were fabricated by the silk-screen printing method. Their structural and dielectric properties were investigated with variation of composition ratio. All BSCT thick films showed a homogeneous structure without presence of the second phase. BSCT film thickness, obtained by three cycle of printing, was approximately $80{\mu}m$. The dielectric constant and dielectric loss of the 3-coated BSCT(50/40/10) thick film were approximately 1700 and 0.07%, respectively.

• The Korean Journal of Ceramics
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• v.3 no.3
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• pp.195-198
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• 1997

Post-firing process of electronic ceramic, such as electroding and encapsultion with resin, often causes damage by thermal shock. The thermal shock behavior of $BaTiO_3$ ceramics was investigated by the down-quench test, where the relative strength retained is determined after the sample is quenched from an elevated temperature into a fixed temperature bath. The critical temperature drop, $\DeltaTc$, was evaluated for three kinds of sintered $BaTiO_3$ ceramics, which were formed by extrustioin, uniaxial pressing using granules, and uniaxial pressing using powders. A drastic loss in strength caused by microcracking was observed for the specimens quenched with $\DeltaT\geq150^{\circ}C$. This concentp can be adopted as a method of the quality control by monitoring the sudden drop of the strength of capacitor products after each exposure to heat.

• Proceedings of the KIEE Conference
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• 1989.07a
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• pp.310-313
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• 1989

The semiconducting bodies were prepared by doping the bariume titanate with $Sb_2O_3,Nb_2O_5$and by subsequent sintering in air. The sintered bodies were annealed between $1100^{\circ}C$ and $1250^{\circ}C$ for 30 minutes to 2 hours in air. The resistivity was measured as a function of temperature from $20^{\circ}C$ to $240^{\circ}C$. The anomalous effect in resistivity occurred all of the $Nb_2O_5$ and $Sb_2O_3$doped barium titanate specimens, which were sintered in air atmosphere, and the most effective PTC effect occurred through 1 hour of sintering time at $1350^{\circ}C$ and 30 minute of annealing time at $1200^{\circ}C$. The resistivity - temperature characteristics seem to be intimately related to oxygen adsorption at grain boundaries and also to the thickness of insulating layers formed at grain boundaries during heat treatment.

• The Korean Journal of Ceramics
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• v.6 no.3
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• pp.309-314
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• 2000

In the present study, preliminary experimental results of the change in the properties of perovskite-type oxides caused by the $^{18}O$- exchange have been reported. Two systems were selected for the exchange, (1) $ATiO_3$(A=Ca,Sr,Ba) and (2) manganese perovskite. The dielectric properties of isotope-exchanged $SrTi^{18}O_3$showed a drastic change from a quantum paraelectricity below 3K to ferroelectric-like behavior with a peak at 23K and an enhanced dielectric constant, 35000 at the peak. On the contrary, the $T_c$ for $BaTiO_3$was found to increase by 0.9K. The observed isotope shift of $T_c$ as well as $T_co$ for the manganese perovskites is correlated with the key parameters controlling the lattice such as $Mn^{3+}$ content, average ionic radius of the A-site cation <$r_A$> ad A-site ionic disorder $\sigma^2$.

• Bulletin of the Korean Chemical Society
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• v.22 no.3
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• pp.298-302
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• 2001

A site preference of niobium atom in Rb2-xLa2Ti3-xNbxO10 (0.0 $\leq$ x $\leq1.0)$ and RbLa2-xCaxTi2-xNb1+xO10 (0.0 $\leq$ x $\leq2.0)$, which are the solid-solutions between Rb2La2Ti3O10 and RbCa2Nb3O10, has been investigated by Raman spectroscopy. The Raman spectra of Rb2-xLa2Ti3-xNbxO10 (0.0 $\leq$ x $\leq1.0)$ gave an evidence that niobium atoms substituted for titanium atoms preferably occupy the highly distorted outer octahedral sites rather than the central ones in triple-octahedral perovskite layers. In contrast, the Raman spectra of RbLa2-xCaxTi2-xNb1+xO10 (0.0 $\leq$ x $\leq2.0)$ showed no clear information for the cationic arrangement in perovskite slabs. This difference indicated that a site preference of niobium atoms is observed only when the linear Rb-O-Ti linkage can be replaced by much stronger terminal Nb-O bond with double bond character. From comparison with the Raman spectroscopic behavior of CsLa2-xA’xTi2-xNb1+xO10 (A’ = Ca and Ba; 0.0 $\leqx\leq2.0)$, it is also proposed that a local difference in arrangement of interlayer atoms causes a significantly different solid acidity and photocatalytic activity of the layered perovskite oxides, despite their crystallographically similar structures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.263-266
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• 2001

In this paper, we investigated dielectric properies for BST thin films that was deposited on MgO/Si substrates using RF magnetron sputtering. In here, MgO film was used to perform that a diffusion b arrier between the BST film and Si substrate and a buffer layer to assist the BST film growth. A d eposition condition for MgO films was RF Power of 50W, substrate temperature of room temperature and the working gas ratio of Ar:O$_2$ were varied from 90:10 to 60:47. Finally we manufactured the cap acitor of Al/BST/MgO/Si/Al structure to know electrical properties of this capacitor through I-V, C-V measurement. In the results, C-V aha racteristic curves was shown a ferroelectric property so we measured P-E. A remanent poliazation and coerceive electric field was present 2$\mu$C/cm$^2$ and -27kV/cm respectively at Ar:O$_2$=90:10. And a va clue of dielectric constant was 86 at Ar:02=90:10.

• Korean Journal of Mineralogy and Petrology
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• v.33 no.4
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• pp.325-337
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• 2020

The Jurassic granitic rocks in the area of Gwangdeoksan located along the boundary between Hwacheon and Cherwon in northern Gyeonggi Massif consist of two-mica granite, garnet-bearing two-mica granite, mica-granite, and porphyritic biotite granite. These granitic rocks are calc-alkaline series and plotted in peraluminious domain in A/CNK vs. A/NK diagram. Petrographical and geochemical data indicate that the porphyritic biotite granite which intruded at the last period originated from distinct parental magma from two-mica granite, garnet-bearing two-mica granite, and mica-granite. On the basis of Rb/Sr vs. Rb/Ba diagram and Al2O3/TiO2 vs. CaO/Na2O, it is inferred the porphyritic biotite granite originated from protolith with less pelitic composition than 3 other granitic rocks. The enriched values of lithophile elements of Cs, Rb, and Ba and negative trough of Nb, P, Ti on spider diagram suggest that the peraluminous Jurassic granitic rocks in Gwangdeoksan area formed in subduction tectonic environment. Whole-rock zircon saturation thermometer indicates that the granitic rocks in the study area were melted at 692-795℃.

• Korean Journal of Materials Research
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• v.7 no.4
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• pp.347-353
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• 1997

BaTiO$_{3}$물질은 뛰어난 유전체로 널리 알려져 왔으며 특히 Heywang등이 제안한 PTCR특성은 이 물질의 응용범위를 세라믹 필터, 회로보호소자, 온도감지소자 및 저항가열장치 등으로 확대시켰다. 이러한 특성의 발현기구는 아직까지 밝혀지지 않은 상태이지만 제 특성을 향상시키기 위한 노력은 계속되어왔다. 특히 개발목적에 맞게 온도에 따른 정저항 특성(PTCR; Positive temperature constnat of resistivity phenomena)을 설계하려는 시도가 계속되어 왔으며 그 중에서도 페로브스카아트계의 2가와 4가의 양이온 자리를 등가나 원자가가 다른 양이온으로 치환하여 특성을 개선하려는 시도가 계속되어 왔다. 특히 $Ca^{2+}$나 Sr$^{2+}$는 $Ba^{2+}$자리를 치환할 수 있는 물질로 개별적인 첨가에 대한 연구는 많은 연구자들에 의해 진행된 상태이지만 최종적인 영향이나 해석에 대해서는 연구자들간에 이견이 많은 상태이다. 이번 실험에서는 BaTiO$_{3}$계에 합성한 (Ca, Sr)TiO$_{3}$를 Ca와 Sr의 상대적인 비를 변화시키면서 전체적인 첨가량을 변화시켜 그에 따른 전기적 특성 및 미세구조를 살펴보았다. (Ca, Sr)TiO$_{3}$의 첨가로 상온저항 및 PTCR특성을 변화시킬 수 있었으며 이를 통해 PTCR물질의 활용범위를 넓힐 수 있는 발판을 마련할 계기가 되었다. 특히 기존의 연구가 주로 개별적인 Ca나 Sr의 첨가에 의한 미세구조와 전기적 특성변화의 연구에 치중해 있었던 것과는 달리 Sr과 Ca을 함께 치환하여 상대적인 비가 특성에 더 중요한 영향을 끼치는 것을 확인하였으며 적절한 합성비를 선택하면 퀴리온도에서의 저항변화폭을 유지하면서 상온저항을 낮출 수 있음을 확인하였다.문했던 연구소인 Shanghai Research Center of Biotechnology, Shanghai Institute of Industrial Microbiology 및 Scientific Research Institute of Food and Fermentation Industry을 소개하고저 한다. 짧은 기간의 방문이라 주로 해당연구소의 자체소개 자료를 중심으로 방문하면서 느낀점을 기술하고저 한다.초염기성암 기원의 사문암이 열수변질작용을 받아 생성되었음을 명확하게 지시하며, 따라서 활석 광석내에 존재하는 녹니석은 활석의 근원 광물로서 녹니석편암 및 녹니석 편마암 매의 녹니석이 활석화되고 남은 잔존광물이 아니라, 주변암에 의해 성분상의 영향을 받은 열수와 사문암과의 변질교대작용에 의한 활석화과정 중에 주로 생성된 것으로 추정된다. 이러한 결과는 연구지역의 활석광상이 초염기성암의 사문암화 작용과 활석화 작용의 두 가지 변질작용에 의해 형성되어졌음을 알려준다.농도 증가 없이 폐 조직에 약 50배 정도의 고농도 cisplatin을 투여할 수 있었으며, 또한 분리 폐 관류 시 cisplatin에 의한 직접적 폐 독성은 발견되지 않았다이 낮았으나 통계학적 의의는 없었다[10.0%(4/40) : 8.2%(20/244), p>0.05]. 결론: 비디오흉강경술에서 재발을 낮추기 위해 수술시 폐야 전체를 관찰하여 존재하는 폐기포를 놓치지 않는 것이 중요하며, 폐기포를 확인하지 못한 경우와 이차성 자연기흉에 대해서는 흉막유착술에 더 세심한 주의가 필요하다는 것을 확인하였다. 비디오흉강경수술은 통증이 적고, 입원기간이 짧고, 사회로의 복귀가 빠르며, 고위험군에 적용할 수 있고, 무엇보다도 미용상의 이점이 크다는 면에서 자연기흉에 대해 유용한 치료방법임에는 틀림이 없으나 개흉술에 비해 재발율이 높고 비용이 비싸다는 문제가 제기되고 있는 만큼 더 세심한 주의와 장기 추적관찰이 필요하리라 사료된다.