• 한국자기학회:학술대회 개요집
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• 한국자기학회 2002년도 동계연구발표회 논문개요집
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• pp.110-111
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• 2002

최근 Y. Masumoto[1]등에 의하여 Co가 도핑된 anatase 구조의 TiO$_2$ 물질에서 상온 강자성 현상이 보고된 이후, 이에 대한 관심이 고조되면서 다른 연구 그룹들에 의해 실험적으로 상온 강자성을 성공하였다는 보고[2,3]가 있으나 현재 그 메커니즘에 대하여 명확한 해석이 되어있지 않고 있기 때문에 이것이 정말 자성반도체의 성질인지 아니면 clustering에 의한 것인지 아직 확실히 밝혀져 있지는 않다. (중략)

• 한국진공학회지
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• 제18권2호
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• pp.141-146
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• 2009

rf magnetron sputtering 법을 이용하여 Pt/Ti/$SiO_2$/Si 기판 위에 buffer layer인 $TiO_2$ 층을 증착한 후 PLZT 강유전체 박막을 증착하였다. PLZT 박막 증착 시 가스 분압비가 박막의 특성에 미치는 영향을 알아보기 위해 Ar/$O_2$ 분압비를 각각 27/1.5 sccm, 23/5.5 sccm, 21/7.5 sccm, 19/9.5 sccm로 변화시키면서 박막을 증착하였다. 이들 박막의 구조적인 특성을 분석하기 위해 X-선 회절법을 사용하였으며 FE-SEM을 이용하여 입자상을 관찰하였다. 또한 박막의 유전특성을 분석하기 위해 Precision LC를 이용하여 이력곡선, 잔류분극, 누설전류를 측정하였다. 산소 분압이 높아질수록 박막의 결정성 및 치밀성이 저하되었으며, (110) 방향에서 (111) 방향으로 우선배향성이 변화하는 것을 확인하였다. 산소 분압비의 변화는 박막 표면 및 강유전 특성에 영향을 미치는 것으로 판단된다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제54권1호
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• pp.13-17
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• 2005

The Pb(Zr/sub 0.52/Ti/sub 0.48/)O₃/(Ba/sub 0.6/Sr/sub 0.4/)TiO₃[PZT/BST] heterolayered thin films were deposited on Pt/Ti/SiO₂/Si substrates by using the RF sputtering method with different RF power. The PZT/BST heterolayered thin films had the tetragonal structure of the PZT phase and BST phase. Increasing the RF power. the intensity of the PZT (100), (110) peaks and BST (111) peaks were decreased and the intensity of the BST (100), (110) peaks were increased. The thickness ratio of the top layered BST thin film and the bottom layered PZT thin film was 2 to1. The atomic concentration of the Ba, Sr, Pb. Zr, Ti atoms were constant in the PZT thin films and BST thin films, respectively. The Pt atom was diffused to the PZT region in the PZT/BST heterolayered thin films deposited at condition of 60[W] RF power. Increasing the frequency, dielectric constant and loss of the PZT/BST heterolayered thin films were decreased. The dielectric constant and loss of the PZT/BST heterolayered thin films deposited with RF power of 90[W] were 406 and 3%, respectively.

• 한국결정성장학회지
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• 제2권2호
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• pp.11-19
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• 1992

$SrTiO_3$미분말은 초음파 분무 열분해법으로 chloride와 nitrate 수용액을 출발용액으로 사용하여 농도를 0.05M과 0.1M로 하였으며 각 농도에 따른 유속의 변화를 0.5cm/sec로 변화시켜 합성하였다. 분말의 형성 과정은 0.05M, 0.05cm/sec 조건에서 단계별 분말을 합성하여 주로 morphorlogy 측면에서 고찰하였다. 출발용액이 chloride 수용액인 경우 SrTiO$_3$미분말을 합성할 수 없었으며 nitrate 수용액인 경우 모든 조건에서 (110)면을 주 peak로 하는 cubic의 순수한 구형의 $SrTiO_3$미분말을 얻을 수 있었다. 평균입자의 크기는 유속이 증가함에 따라 $0.49{\mu}m$에서 $0.55{\mu}m$로 증가하였다. 출발액적의 크기는 $14.3{\mu}m$이었으며 단계별 입자의 형태는 1, 2단계에서 용매의 증발에 의해 매우 porous하였으며 불규칙하였고, 3, 4, 5단계를 지나는 동안 점차 둥근 형태로 형성되었다.

• E2M - 전기 전자와 첨단 소재
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• 제10권3호
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• pp.239-246
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• 1997

The ZnO is stabilize dielectric constant over a broad temperature range because its addition makes the relaxation time short. In this study, the composite oxide material (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ was mixed by ZnO additive material and the dielectric polarization characteristics was studied. The relative density was over 90[%] at all specimen in the structural characteristics. Among of the specimen, the relative density of (B $a_{0.85}$ $Ca_{0.15}$)Ti $O_{3}$ with ZnO (0.4mol) has a 95[%]. The grain size of composite oxide material with an increasing ZnO increased and it was 1.0[.mu.m]-1.22[.mu.m]. In the electrical characteristics, the charge and discharge current was increased by ZnO addition. The dielectric relaxation time was increased by space charge polarization at above 110[.deg. C] and the dielectric relaxation time was fixed by space charge polarization of para-dielectric layer at below 110[.deg. C]. The dielectric relaxation time was maximum when the grain size was small. The dielectric relaxation time is decreased with an additive material ZnO and interface polarization, existing void at the grain and grain boundary. The remnant polarization is increased and the coercive electric field is decreased by ZnO.

• 한국세라믹학회지
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• 제27권8호
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• pp.1050-1054
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• 1990

Rutile(TiO2) single crystals were grown by FZ method. Feed rod was sintered in the longitudinal tube-shaped furnace at 135$0^{\circ}C$ and optimum growth condition was growth rate 5-8mm/hr, rotation rate 30-40rpm. When crystal was growing, atomosphere was oxidized condition, and grown single crystal was annealed at 110$0^{\circ}C$. The rutile single crystals were oriented to [001] direction and color change of single crystals were related to atmosphere, and difference of electric conductivity and resistance was due to the fact above.

• 한국환경과학회지
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• 제28권1호
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• pp.65-73
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• 2019

The catalytic activity of Ni-0.2%YSZ (Yttria-Stabilized Zirconia) with different promoters was evaluated for $CO_2$ methanation. The catalysts were weighed for mixing and they were dried at $110^{\circ}C$ for molding into disks. The concentration of $CO_2$ and $CH_4$ for conducting of $CO_2$ methanation were analyzed by gas chromatography and the physical characteristics of the disk-type catalyst formed were analyzed by X-ray diffraction, scanning electron microscope and energy dispersive x-ray spectrometer. The addition of $CeO_2$ as a promoter for Ni-0.2%YSZ (denoted as Ni-5%Ce-0.2%YSZ) resulted in the highest $CO_2$ methanation. It also showed catalytic activity at a low temperature($200^{\circ}C$). Following this, $ZrO_2$, $SiO_2$, $Al_2O_3$ and $TiO_2$ were added to Ni-5%Ce-0.2%YSZ to compare the $CO_2$ methanation, and the highest efficiency was found for. Ni-1%Ti-5%Ce-0.2%YSZ Then, the concentration of Ti was increased to 10% and the catalytic activity was estimated using seven different types of commercial $TiO_2$. In conclusion, ST-01 $TiO_2$ showed the highest efficiency for $CO_2$ methanation.

• 전기화학회지
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• 제5권3호
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• pp.106-110
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• 2002

Ethylene carbonate(EC), propylene carbonate(PC), dimethyl carbonate(DMC)의 가소제와 $LiPF_6$ 리튬염 및 $TiO_2$ 충진제를 이용하여 젤형 polyacrylonitrile(PAN) 전해질을 제조하였다. 고분자 전해질의 전기화학적 안정성, 이온전도도, 리튬전극과의 호환성 등의 전기화학적 특성과 기계적 특성을 조사하였다. 이러한 고분자 전해질을 이용하여 조립된 리튬이차전지의 충방전 특성을 조사하였다 EC, PC 혼합 가소제를 이용하여 제조된 고분자 전해질은 $TiO_2$가 첨가됨에 따라 고분자 전해질이 견딜 수 있는 최대 하중이 2배 가깝게 증가하였다. EC, PC혼합 가소제와 $TiO_2$가 혼합된 고분자 전해질은 상온에서 $2\times10^{-3}S/cm$의 이온전도도를 나타내었고, 4.5V까지 전기화학적으로 안정하였다. 리튬금속을 사용하여 제조된 셀의 임피던스 결과에서도 EC, PC 혼합 가소제와 $TiO_2$가 혼합된 고분자 전해질이 20일 동안 계면 저항 $130\Omega$으로 가장 안정하였다. $LiCoO_2$ 양극과 리튬 음극, $TiO_2$가 혼합된 고분자 전해질로 구성된 전지는 충방전효율이 1C 방전속도에서 $90\%$를 나타내었다.

• 한국표면공학회지
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• 제36권1호
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• pp.14-21
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• 2003

Thin films of ZrO$_2$ and TiO$_2$ were deposited on Si(100) substrates using RF magnetron sputtering technique. To study an influence of the sputtering parameters, systematic experiments were carried out in this work. XRD data show that the $ZrO_2$ films were mainly grown in the [111] orientation at the annealing temperature between 800 and $1000^{\circ}C$ while the crystal growth direction was changed to be [012] at above $1000^{\circ}C$. FT-IR spectra show that the oxygen stretching peaks become strong due to $SiO_2$ layer formation between film layers and silicon surface after annealing, and proved that a diffusion caused by either oxygen atoms of $ZrO_2$ layers or air into the interface during annealing. Different crystal growth directions were observed with the various deposition parameters such as annealing temperature, RF power magnitude, and added $O_2$ amounts. The growth rate of $TiO_2$ thin films was increased with RF power magnitude up to 150 watt, and was then decreased due to a sputtering effect. The maximum growth rate observed at 150 watt was 1500 nm/hr. Highly oriented, crack-free, stoichiometric polycrystalline $TiO_2$<110> thin film with Rutile phase was obtained after annealing at $1000^{\circ}C$ for 1 hour.

• 한국재료학회지
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• 제20권7호
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• pp.374-378
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• 2010

$MgTiO_3$ thin films were prepared by r.f. magnetron sputtering in order to prepare miniaturized NPO type MLCCs. $MgTiO_3$ films showed a polycrystalline structure of ilmenite characterized by the appearance of (110) and (202) peaks. The intensity of the peaks decreased with an increase in the chamber pressure due to the decrease of crystallinity which resulted from the decrease of kinetic energy of the sputtered atoms. The films annealed at $600^{\circ}C$ for 60min. showed a fine grained microstructure without micro-cracks. The grain size and roughness of the $MgTiO_3$ films decreased with the increase of chamber pressure. The average surface roughness was 1.425~0.313 nm for $MgTiO_3$ films prepared at 10~70 mTorr. $MgTiO_3$ films showed a dielectric constant of 17~19.7 and a dissipation factor of 2.1~4.9% at 1MHz. The dielectric constant of the films is similar to that of bulk ceramics. The dielectric constant and the dissipation factor decreased with the increase of the chamber pressure due to the decrease of grain size and crystallinity. The leakage current density was $10^{-5}\sim10^{-7}A/cm^2$ at 200kV/cm and this value decreased with the increase of the chamber pressure. The small grain size and smooth surface microstructure of the films deposited at high chamber pressure resulted in a low leakage current density. $MgTiO_3$ films showed a near zero temperature coefficient and satisfied the specifications for NPO type materials. The dielectric properties of the $MgTiO_3$ thin films prepared by sputtering suggest the feasibility of their application for MLCCs.