• Journal of the Korean Ceramic Society
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• v.31 no.6
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• pp.651-659
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• 1994

BaTiO3 ceramics were sintered on Al2O3, MgAl2O4, MgO and Mg-, Ca-, Y-stabilized zirconia setters. Then the influence of setters on the microstructure of BaTiO3 ceramics and the stability of setters were investigated by SEM, EDAX and XRD analyses. The microstructure of BaTiO3 ceramics sintered on Al2O3, MgAl2O4, MgO and Mg-PSZ showed large grain growth, but little grain growth on Ce-TZP(Tetragonal Zirconia Policrystal). Mg-PSZ(Partially Stabilized Zirconia), Ca-PSZ, Ce-TZP setters showed extensive phase transformation. Y-TZP and fused Y-SZ (Stabilized Zirconia) setters were stable. The liquid sintering aids of BaTiO3 ceramics accelerate mass transport. The reaction of SrTiO3 in BaTiO3 with ZrO2 resulted in the formation of SrZrO3.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1097-1098
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• 2006

The Powder characteristics and sintering behavior of $SiO_2$ coated $BaTiO_3$ were studied. Silica coated $BaTiO_3$ powders were prepared by sol-gel method. The particle size of the $BaTiO_3$ powders were $\sim35$ nm and the thickness of the $SiO_2$ coating layer was $\sim5$ nm. As the $SiO_2$ content increased, the $SiO_2$ layers improved the powder dispersion. The Zeta potential of $SiO_2$ coated $BaTiO_3$ was getting close to that of pure silica with a more negative charge, compared with that of the uncoated $BaTiO_3$. The onset temperature of shrinkage curves shifted to higher temperatures with increasing $SiO_2$ contents

• Journal of the Microelectronics and Packaging Society
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• v.3 no.1
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• pp.25-32
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• 1996

본 연구에서는 BaTiO3에 Sr과 Pb를 치환시켜TiO3 조성의 세라믹 유전체를 제조한 후 페로브스카이트형 Ba(Cu, Mo)O3를 저융점 flux 로 첨가하여 120$0^{\circ}C$ 이하의 여러온도에 서 소결을 행하였으며 flux 첨가량의 변화에 따른 소결거동 및 유전 특성의변화를 조사하였 다. 이러한 저온 소결용 유전체 세라믹스가 MLCC의 응용시 Pt-Pd계의합금을 내부전극으로 사용가능성을 검토하였다. Flux를 4mol%첨가한 TiO3-0.04Ba(Cu,Mo)O3 조성의 유전체는 120$0^{\circ}C$의 온도에서 2시간 소결했을 경우 소결밀도는 이론밀도의 95% 에 근접하였으며 이때 의 비유전율은 8000이상을 나타내었다. 이러한 소결 온도의 감소는 저융점인 ba(Cu,Mo)O3 계의 flux가 첨가되면서 비교적 낮은 온도에서 액상을 형성하여 소결을 촉진시켰기 때문으 로 사료된다.

• Proceedings of the Korea Society for Energy Engineering kosee Conference
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• 2003.05a
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• pp.685-688
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• 2003

BaTiO$_3$ 분말을 Ba(OH)$_2$ㆍ8$H_2O$와 아나타제형의 TiO$_2$ㆍx$H_2O$를 이용하여 수열합성법에 의해 제조하였다. Autoclave 반응기를 이용한 본 실험의 경우, BaTiO$_3$ 분말을 생성하기 위해 반응온도, 용질의 농도 등과 같이 BaTiO$_3$ 합성에 관여하는 반응변수를 변화시켜, 각각의 실험조건이 어떠한 영향을 미치는지를 조사하였다 수열합성법에 의해 합성된 BaTiO$_3$의 전화율은 온도와 농도 증가에 따라 높아지는 현상을 보였으며, 열역학적으로 계산된 최대 전화율에 접근하였다. 또한 반응온도와 농도의 증가에 의해 생성된 BaTiO$_3$는 균일한 입도 분포와 구형에 가까운 형상을 나타내었다. 따라서 농도를 높이는 조건이 전화율과 생산성을 모두 높일 수 있는 방법이라는 것을 확인할 수 있었다.

• Journal of the Korean Magnetics Society
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• v.16 no.6
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• pp.283-286
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• 2006

We have studied the role of ${\alpha}-Al_{2}O_{3}$ buffer layer as a diffusion barrier in the Ba-ferrite/$SiO_{2}$ magnetic thin films for high-density recording media. In the interface of amorphous Ba-ferrite $(1900-{\AA}-thick)/SiO_{2}$ thin film during annealing, the interfacial diffusion started to occur at ${\sim}700^{\circ}C$. As the annealing temperature increased up to $800^{\circ}C$, the interfacial diffusion abruptly proceeded resulting in the high interface roughness and the deterioration of the magnetic properties. In order to control the interfacial diffusion at the high temperature, we introduced ${\alpha}-Al_{2}O_{3}$ buffer layer ($110-{\AA}-thick$) in the interface of Ba-ferrite/$SiO_{2}$ thin film. During the annealing of Ba-ferrite/${\alpha}-Al_{2}O_{3}/SiO_{2}$ thin film even at ${\sim}800^{\circ}C$, the interface was very smooth. The magnetic properties, such as saturation magnetization and intrinsic coercivity, were also enhanced, due to the inhibition of interfacial diffusion by the ${\alpha}-Al_{2}O_{3}$ buffer layer. Our study suggests that the ${\alpha}-Al_{2}O_{3}$ buffer layer act as a useful interfacial diffusion barrier in the Ba-ferrite/$SiO_{2}$ magnetic thin films.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.842-850
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• 2004

We have investigated on the preparation of BaTiO$_3$ powder at the system of BaO$_2$-TiO$_2$-Reduction ag.-PSCA by SHS. C and Mg were used as reduction agent, and NaCl was used as PSCA (Particle Size Control Agent). The effects of the various reduction agent and its concentration, particle size control agent, reaction mixture mass on the product in the preparation of BaTiO$_3$ powder at the optimum system by SHS were investigated. The optimum conditions for reaction system and composition were BaO$_2$+TiO$_2$+0.11 Mg +0.2C+0.75NaCl in the As atmosphere. NaCl as PSCA showed the effect of controlling the particle size of product as well as the combustion temperature. The particle size of BaTiO$_3$ synthesized at the optimum condition was about 0.5 ${\mu}{\textrm}{m}$. And as the mixture mass for the reaction was increased, the more stable combustion wave appeared. We have conducted the sintering experiment at the temperature of 130$0^{\circ}C$, the time of 2 h and the atmosphere of air to measure the dielectric properties of BaTiO$_3$ synthesised in this work, and the sample sintered in this condition showed 2,290 of dielectric constant at 10$0^{\circ}C$ and 13,890 at curie point (129$^{\circ}C$).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.286-287
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• 2006

Barium titanate ($BaTiO_3$) glycolate particles were synthesized at temperature as low as $100^{\circ}C$ through glycothermal reaction by using $Ba(OH)_2{\cdot}8H_2O$ and amorphous titanium hydrous gel as precursors and ethylene glycol as solvent. The particle size and morphology of $BaTiO_3$ glycolate powders can be controlled by varying the reaction conditions such as the reaction temperature and Ba:Ti molar ratio of starting precursors. After glycothermal treatment at $220^{\circ}C$ for 24 h in 1.25:1(Ba:Ti), the average particle size of the $BaTiO_3$ glycolate powder was about 200-400 nm and low agglomeration. $BaTiO_3$ powders were formed by heat-treating the glycolate powder in air at $500-1000^{\circ}C$. As a result, the size of $BaTiO_3$ crystallites changed from around 50-300 nm. It is also demonstrated that the size and shape of $BaTiO_3$ particles investigated as a function of calcination temperature. The $BaTiO_3$ particles obtained from optimum synthesis condition were pressed, sintered and measured for the dielectric property. The $BaTiO_3$ ceramics sintered at $1250^{\circ}C$ for 2 h had 98 % of theoretical density. The ceramics have an average grain size of about $1\;{\mu}m$ and displays the high dielectric constant (~3100) and low dielectric loss (<0.1) at room temperature.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2001.11a
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• pp.36-36
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• 2001

$BaTiO_3$는 현재 전기 전자 부속 산업엣 필수적인 재료로서, multilayer capacitor,positive temperature coefficient(PTC) resistor, grain-boundary battier layer capacitor(GBBLC)등에 쓰이고 있다. $BaTiO_3$의 전기적 특성을 최대화하기 위해서는 미세구조가 최적화 되어야만 하는데 일반적으로 수 마이트로 이내의 작고 균일한 크기의 입자크기가 바람직하다. 그러나 $BaTiO_3$계에서 화학양론의 조성이 정확하게 일치하지 않거나 $La^{3+}$나 $Nb^{5+}$같은 첨가제가 들어가지 않으면 비정상 입자 성장은 자발적으로 일어난다. 그러나 첨가제는 $BaTiO_3$의 강자성 특성에 영향을 주게 되므로 첨가제 없이 비정상 입자 성장을 억제할 수 있는 것이 바람직한 방법이며, 이 것이 본 실험의 목표이다. 본 실험에서는 0.4-mol%-$TiO_2$가 첨가된 $BaTiO_3$ 분말을 디스크 형태로 성형하여 $H_2$ 분위기, 1250에서 5시간동안 열처리한 후, 공기 중, 1300도에서 48시간까지 소결한 후 미세조직을 관찰하였다. 소결 전에 $H_2$ 분위기에서 열처리를 함으로서 초기 입자 크기는 증가하게 되고 이로 인한 계의 성장 구동력 감소로 비정상 입자 성장이 억제되었으며 균일하고 미세한 입자 크기를 가지는$BaTiO_3$ 소결체를 얻을 수 있었다. 또한 비정상이 억제되지 않은 $BaTiO_3$의 유전 특성보다 우수한 유전 특성을 나타내었다. 본 실험을 통해서 첨가제를 사용하지 않고 우수한 유전 특성을 가지는 미세한 균일한 입자의 $BaTiO_3$를 제조하는 새로운 기술을 개발하였다.

• Progress in Superconductivity and Cryogenics
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• v.10 no.1
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• pp.1-5
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• 2008

The effect of $BaCeO_3$ doping on the critical current density of YBCO film by TFA-MOD method was studied. $BaCeO_3$ doping was made by two method; one is direct addition of $BaCeO_3$ nano-sized powder prepared by citrate process followed by grinding with planetary ball mill for 10 hours. Another is addition of Ba-Ce precursor solution prepared with Ba-acetate and Ce acetate dissolved in TFA to the YBCO-TFA precursor solution. The film was made by standard dip coating and heat treatment process with conversion temperature of $790^{\circ}C$ in 1000 ppm oxygen containing moisturized Ar gas atmosphere. The direct addition of $BaCeO_3$ powder resulted in YBCO film with good epitaxial growth and no evidence of second phase formation. The addition through precursor solution resulted in the increase of critical current density upto 30 at% doping and uniform dispersion of $BaCeO_3$ fine inclusion was confirmed by SEM-EDX.

• Journal of Magnetics
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• v.11 no.4
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• pp.164-166
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• 2006

We have investigated the dielectric and magnetic properties of ferroelectric-antiferromagnetic $BaTiO_{3}-LaMnO_{3}$ composite with changing relative mole percents. Due to high sintering temperature, i.e. $1150^{\circ}C$, the Ba ion in $BaTiO_{3}$ seems to diffuse into $LaMnO_{3}$; resulting in $BaTiO_{3}-(La,Ba)MnO_{3}$ ferroelectric-ferromagnetic composite. At room temperature, $0.9BaTiO_{3}-0.1LaMnO_{3}$ composite exhibits considerable magnetization (${\sim}0.7\;emu/g\;at\;2000\;Oe$) and low coercive field (${\sim}5\;Oe$). Also it exhibits high dielectric constant (${\sim}560$) and low loss (${\sim}0.08$) at 10 kHz. This result may imply that $BaTiO_{3}-LaMnO_{3}$ could be suitable for a low leakage multiferroic composite.