• 한국전기전자재료학회논문지
• /
• 제35권2호
• /
• pp.103-118
• /
• 2022

With the recent increase in demand for electronic devices, multi-layer ceramic capacitors (MLCCs) have become the most important core component. In particular, the next-generation MLCC with extremely high reliability is required for the 4^th industrial revolution and electric vehicle applications. Therefore, it is necessary to develop dielectric ceramic materials with high dielectric properties and reliability. During the decades, electrical properties of BaTiO₃ based dielectric ceramics, which have been widely used in MLCC industrial field, have been improved by microstructure and defect chemistry control. However, electrical properties of BaTiO₃ have reached their limits, and new types of dielectric materials have been widely studied. Based on these backgrounds, this report presents the recent development trends of BaTiO₃-based dielectric materials for the next-generation MLCCs, and suggests promising candidates to replace BaTiO₃ ceramics.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 1999년도 춘계학술대회 및 발표대회 강연 및 발표논문 초록집
• /
• pp.34-34
• /
• 1999

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제50권11호
• /
• pp.550-554
• /
• 2001

$(Ba_{0.6}Sr_{0.4}Ca_x)TiO_3 + yAl_2O_3$ wt% (x=0.10, 0.15, 0.20, y=0~3.0) ceramics were fabricated by the mixed-oxide method, and their structural and dielectric properties were investigated with variation of composition ratio and $Al_2O_3$ doping content. As results of the X-ray diffraction and microstructure analysis, all BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with an increase of $Al_2O_3$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing $Al_2O_3$doping content. The dielectric loss is minimum at BSCT doped with 1.5wt% $Al_2O_3$content. The tunability was decreased with increasing an Ca content and the BSCT(50/40/10) specimen doped with 2.0wt% $Al_2O_3$content showed the maximum value of 4.2%.

• 한국세라믹학회지
• /
• 제36권2호
• /
• pp.136-144
• /
• 1999

텅스템브론즈형 고주파 유전체의 $BaORe_2O_3TiO_2$(BLT)와 $BaO(Nd({0.77}Y_{0.23})_2O_34TiO_2(B(NY)T)$의 결정구조를 Rietveld 정밀화법으로 분석하였다. 양이온은 X-선 데이터로부터, 산소이온은 중성자 데이터로부터 정밀화한 'combined법'에 의해 가장 신뢰성이 높은 결정구조분석 결과를 얻었다. Mateeva 등이 처음 제시한 결정구조의 결정학적 모순점을 해결하였다. BaORe2O34TiO2(Re=La, Nd, Y) 유전체는 $3\times2$개의 페롭스카이트 블록과 이 블록사이에 형성된 4개의 pentagon-channel로 이뤄진다. Ti-O6팔면체는 tilted 및 변형된 구조를 갖고 있고, 이에 의해 같은 z-층에 있는 Ba 및 Re 이온의 변위되어 초격자(c$\approx$ 7.6$\AA$)를 형성된다. Re 이온반경이 작은 B(NY)T의 Ti-O6 팔면체가 tilting 및 변형이 큰 것으로 나타났다. 유전상수 $\varepsilon_{\gamma}$과 온도계수 $au_\varepsilon$은 BLT의 경우 각각 $109.5, -180 ppm/^{\circ}C$였고, B(NY)T 경우 $76, +40ppm/^{\circ}C$이었다. Re 이온 크기가 작은 시료의 $\tau$$\varepsilon$이 +값을 나타내었다. 복합 페롭스카이트에서 관찰되는 $\tau_\varepsilon$과 팔면체 tilting과의 관계를 본 텅스텐 브론즈 구조재료에서 고찰하였다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1988년도 춘계학술대회 논문집
• /
• pp.82-83
• /
• 1988

• Bulletin of the Korean Chemical Society
• /
• 제16권10호
• /
• pp.908-911
• /
• 1995

The EPR spectra of Cu-or Zr-doped BaTiO3 ceramics exhibited absorption signals with g∥=2.380 and g⊥=2.063 which are assigned to Ba1+(Ba2+ + e'→Ba1+) ion reduced by an electron that was produced from the oxygen vacancy (VO..). The intensity of these signals decreased as the temperature increased indicating that Ba1+ was changed to Ba2+ as the temperature increased. These ceramics also showed the EPR signal with g=1.997 around TC which arises from ionized Ba-vacancies, VBa'(VBa + e'→VBa'. In the orthorhombic and tetragonal phase region g=1.997 signal was not seen. The electrons generating from the oxidation of Ba1+ and ionized Ba-vacancies may contribute to a space charge which is responsible for a dielectric relaxation of these samples.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
• /
• pp.402-405
• /
• 2001

$(Ba_{0.6-x}Sr_{0.4}Ca_{x})TiO_{3}$ (x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their stuctural and dielectric properties were investigated with variation of composition ratio and an amount of $Al_{2}O_{3}$ (0.5, 1.0, 1.5. 2.0, 3.0 wt%) doping content. As a result of the X-ray diffraction BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with increase an $Al_{2}O_{3}$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing an amount of $Al_{2}O_{3}$ doping content. The dielectric loss is minimum for BSCT doped with 1.5wt% $Al_{2}O_{3}$ content. The tunability was decreased with increasing an Ca content and is about 4.2% for BSCT(50/40/10) doped with 2.0wt% $Al_{2}O_{3}$ content.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 추계학술대회 논문집
• /
• pp.402-405
• /
• 2001

(Ba$\_$0.6-x/Sr$\_$0.4/Ca$\_$x/)TiO$_3$(x=0.10, 0.15, 0.20) ceramics were fabricated by the mixed-oxide method and their structural and dielectric properties were investigated with variation of composition ratio and an amount of Al$_2$O$_3$(0.5, 1.0, 1.5, 2.0, 3.0 wt%) doping content. As a result of the X-ray diffraction BSCT specimens showed dense and homogeneous structure without presence of the second phase. The sintered density was decreased with increase an Al$_2$O$_3$ doping content. The Curie temperature and relative dielectric constant at room temperature were decreased with increasing an amount of Al$_2$O$_3$ doping content. The dielectric loss is minimum for BSCT doped with 1.5wt% Al$_2$O$_3$ content. The tunability was decreased with increasing an Ca content and is about 4.2% for BSCT(50/40/10) doped with 2.0wt% Al$_2$O$_3$ content.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.288-288
• /
• 2007

본 연구에서 내환원성 $BaTiO_3$의 PTCR(Positive Temperation Coefficient Resistance) 특성 및 미세구조에 대한 분쇄 및 출발 원료들의 하소 조건의 영향을 연구하였다. $BaCO_3$, $TiO_2$, $CeO_2$를 Attrition milling 하여 1차 혼합 및 분쇄한 후 건조하여 혼합분말을 얻었으며, $(Ba_{1-x}Ce_x)TiO_3$를 합성하기 위하여 $1000^{\circ}C{\sim}1200^{\circ}C$ 공기중에서 하소하였다. 각 하소온도에서 제조한 $(Ba_{1-x}Ce_x)TiO_3$에 첨가제를 2차 혼합하고 초미분쇄하여 분말을 제조하였다. 직경 5mm 의 시편을 제조하여 환원 및 재산화 분위기에서 소결을 한 후 상온저항값 및 R-T특성을 측정하였고 SEM 을 통해 미세구조를 관찰하였다. 또한 하소 후 온도에 따른 상분석을 XRD를 통하여 분석하였다. 그 결과 하소온도가 증가함에 따라 상온저항값은 감소하는 경황을 보였으며 PTC특성은 감소하다가 증가하는 경향을 보였다. 초미분쇄에 따른 입자크기는 $1{\mu}m$이하로 작아졌으며 미립화가 됨에 따라 하소/소결온도에 앙향을 줄 것으로 사료된다.

• Journal of Magnetics
• /
• 제14권3호
• /
• pp.117-119
• /
• 2009

Polycrystalline samples of LaFe$O_3$-BaTi$O_3$ were synthesized to examine the structural and magnetic behavior. X-ray diffraction confirmed that the ceramics had tetragonal symmetry with less tetragonal strain (c/a) than BaTi$O_3$. The magnetic hysteresis measured at room temperature suggested that the magnetic nature deviates from that of the parent LaFe$O_3$, which has antiferromagentic with a G-type spin structure. Improved magnetic behavior of the solid solution compound might be due to the increase in the canting angle of the spin. The presence of oxygen vacancies and fluctuating Fe valence, arising from the substitution of $Ba^{2+}$ and $Ti^{4+}$ at the A- and B-sites of the lattice, might contribute to bulk magnetization. The temperature dependent magnetization indicated that magnetization was higher at low temperatures and showed a decreasing trend with increasing temperature to room temperature. The magnetic transition temperature of these samples was 665 K and 743 K for the mixed system and LaFe$O_3$, respectively.