• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.8
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• pp.852-858
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• 2004

An alkoxide-based sol-gel method was used to fabricate $Ba_{0.6}Sr_{0.4}TiO_{3}$thin films doped by Bi from 5 to 20 mol% on a Pt/Ti/$SiO_2$/Sisubstrate. The structural and dielectric properties of BST thin films were investigated as a function of Bi dopant concentration. The dielectric properties of the Bi doped BST films were strongly dependent on the Bi contents. The dielectric constant and dielectric loss of the films decreased with increasing Bi content. However, the leakage current density of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_{3}$ thin film showed the lowest value of 5.13$\times 10^{-7} A/{cm}^2$ at 5 V. The figure of merit (FOM) reached a maximum value of 32.42 at a 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}TiO_{3}$thin films. The dielectric constant, loss factor, and tunability of the 10 mol% Bi doped $Ba_{0.6}Sr_{0.4}Tio_{3}$ thin films were 333, 0.0095, and 31.1%, respectively.

• Journal of the Korean Ceramic Society
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• v.49 no.1
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• pp.100-104
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• 2012

Barium zincoborate (BZB) glass was added to $Ba_{0.5}Sr_{0.5}TiO_3$, and sintered at $875^{\circ}C$ for 2 h in air. When the BZB glass was added in quantities ranging from 15 to 20 wt%, the relative bulk density ranged from 93.1% to 94.2%, while the density decreased to roughly 81% thereafter up to 30 wt% glass addition. Quantitative XRD analysis showed that the $Ba_{0.5}Sr_{0.5}TiO_3$ filler was significantly dissolved into the BZB glass. However, no secondary phase was identified by XRD up to 30 wt% glass addition. The dielectric constant was about 130 to 140 at 1MHz up to 20 wt% BZB glass addition, while it decreased to about 60 thereafter, which may be ascribed to decreased density, partial dissolution of the $Ba_{0.5}Sr_{0.5}TiO_3$, and associated changes in the glass composition. The dielectric loss of the 20 wt% glass added specimen was 0.008.

• Macromolecular Research
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• v.14 no.4
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• pp.430-437
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• 2006

The ultra-drawing process of an ultra high molecular weight polyethylene (UHMWPE) gel film was examined by incorporating linear low-density polyethylene (LLDPE) and $BaTiO_3$ nanoparticles. The effects of LLDPE and the draw ratios on the morphological development and mechanical properties of the nanocomposite membrane systems were investigated. By incorporating $BaTiO_3$ nanoparticles in the UHMWPE/LLDPE blend systems, the ultra-drawing process provided a highly extended, fibril structure of UHMWPE chains to form highly porous, composite membranes with well-dispersed nanoparticles. The ultra-drawing process of UHMWPE/LLDPE dry-gel films desirably dispersed the highly loaded $BaTiO_3$ nanoparticles in the porous membrane, which could be used to form multi-layered structures for electronic applications in various embedded, printed circuit board (PCB) systems.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.307-314
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• 2008

The influence of a moist atmosphere on $90^{\circ}$ domain switching under a sustained electric field, stress corrosion cracking of an indentation crack in water and an aggressive solution, and the relation between penetrating crack propagation and domain switching were studied using $BaTiO_3$ single crystal. The results indicate that enlarging the domain switching zone and crack propagation could be facilitated by a moist atmosphere or an aggressive solution due to the indentation residual stress. A moist atmosphere exerts remarkable influence upon the polarization of $BaTiO_3$ single crystal under a sustained electric field, and the surface energy of the c domain was much lower than that of the a domain. Domain switching ahead of a penetrating indentation crack tip was an essential requirement for crack propagation under constant stress.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.305-306
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• 2006

자동차의 난방 열원은 HVAC(Heating, Ventilating & Air Conditioning)에 내장되어 있는 히터코어 (Heater Core) 에서 공급하게 되며, 이 히터코어는 엔진에서 가열된 냉각수 열원을 이용하게 된다. 그러나 최근 디젤 엔진의 경우 연소효율의 개선과 CEGR(Cooled Exhaust Gas Recirculation) 시스템의 적용으로 냉각부하가 증가하여 냉각수가 가지는 가용 열원이 기종보다 약 30~40% 정도 저하되고 있다. 따라서 디젤 자동차 및 하이브리드용 자동차의 난방 보조 히터의 국산화 개발이 시급해진 상황이며 초정밀, 고효율 보조 히터의 개발이 요구되고 있다. 현재 적용되고 있는 보조 히터 중에서 PTC 히터는 PTC 소자의 발열을 이용하여 공기를 직접 가열하기 때문에 추가적인 연료소비가 없고 소형 및 저가라는 장점이 있다. PTC 세라믹 소자는 $BaTiO_3$를 모체로 하며, 이의 특성 항상 및 제어를 위해서는 적절한 dopant를 선택하여 균일하게 doping 해야 한다. 지금까지 dopant에 따른 구성 요소 및 역할은 비교적 잘 알려져 있다. 하지만, 자동차용으로 사용되기 위해서는 12V의 저전압에서 동작해야 하며, 또한 소자의 두께가 얇아지게 됨에 따라서 발생하는 전기적 short와 같은 문제점들을 해결하여야 한다. 따라서 본 연구에서는 PTC 세라믹 소자에서 도펀트 종류와 양 조절을 통한 저저항을 확보하고, PTC 세라믹 소자의 박막화를 달성하고자 하였다.

• Journal of Powder Materials
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• v.26 no.2
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• pp.119-125
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• 2019

Piezoelectric energy harvesting technology is attracting attention, as it can be used to convert more accessible mechanical energy resources to periodic electricity. Recent developments in the field of piezoelectric energy harvesters (PEHs) are associated with nanocomposites made from inorganic piezoelectric nanomaterials and organic elastomers. Here, we used the $BaTiO_3$ nanoparticles and piezoelectric poly(vinylidene fluoride) (PVDF) polymeric matrix to fabricate the nanocomposites-based PEH to improve the output performance of PEHs. The piezoelectric nanocomposite is produced by dispersing the inorganic piezo-ceramic nanoparticles inside an organic piezo-polymer and subsequently spin-coat it onto a metal plate. The fabricated organic-inorganic piezoelectric nanocomposite-based PEH harvested the output voltage of ~1.5 V and current signals of ~90 nA under repeated mechanical pushings: these values are compared to those of energy devices made from non-piezoelectric polydimethylsiloxane (PDMS) elastomers and supported by a multiphysics simulation software.

• Journal of the Korean Ceramic Society
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• v.43 no.6 s.289
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• pp.362-368
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• 2006

Epitaxial $Ba_{0.5}Sr_{0.5}TiO_3$ (BSTO) thin films have been grown on TiN buffered Si (001) substrates by Pulsed Laser Deposition (PLD) method and the effects of substrate temperature and oxygen partial pressure during the deposition on their dielectric properties and crystallinity were investigated. The crystal orientation, epitaxy nature, and microstructure of oxide thin films were investigated using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Thin films were prepared with laser fluence of $4.2\;J/cm^2\;and\;3\;J/cm^2$, repetition rate of 8 Hz and 10 Hz, substrate temperatures of $700^{\circ}C$ and ranging from $350^{\circ}C\;to\;700^{\circ}C$ for TiN and oxide respectively. BSTO thin-films were grown on TiN-buffered Si substrates at various oxygen partial pressure ranging from $1{\times}10^{-4}$ torr to $1{\times}10^{-5}$ torr. The TiN buffer layer and BSTO thin films were grown with cube-on-cube epitaxial orientation relationship of $[110](001)_{BSTO}{\parallel}[110](001)_{TiN}{\parallel}[110](001)_{Si}$. The crystallinity of BSTO thin films was improved with increasing substrate temperature. C-axis lattice parameters of BSTO thin films, calculated from XRD ${\theta}-2{\theta}$ scans, decreased from 0.408 m to 0.404 nm and the dielectric constants of BSTO epitaxial thin films increased from 440 to 938 with increasing processing oxygen partial pressure.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.355-357
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• 1995

Pt(80nm)/$SiO_2$(150nm)/Si 기판위에 $Ba_{0.7}Sr_{0.3}TiO_3$ 박막을 rf-magnetron Sputtering 방법을 이용하여 기판온도 590$^{\circ}C$에서 33nm 두께를 증착했을 때 비유전율은 268 이었다. 비유전율이 3.9인 $SiO_2$와 비교했을 때 유효 두께인 Tox는 0.45nm 이었다. 누설 전류 밀도는 1.5V 전압을 인가했을 때 $4.21\times10^{-7}A/cm^2$이었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.407-410
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• 1998

The characteristics of $(Ba,Sr)TiO_3$[BST] thin films with the variation of $O_2/Ar$ ratio in sputtering gas deposited on $RuO_2$ bottom electrode were investigated. Dielectric constant of BST film increases from 135 to 190 with increasing oxygen partial pressure from 10 to 50, which is mainly due to the improved crystallinity of BST film. The instability of $RuO_2$ surface in $BST/RuO_2$ interface and the increase in the surface roughness of BST thin films with higher $O_2/Ar$ ratio appeared to play an important roles on the degradation of the leakage current characteristics of $Al/BST/RuO_2$ capacitor with various $O_2/Ar$ ratio in sputtering gas. As a consequence, the leakage current of BST thin film showed the lowest value of $1.9{\times}10^{-7}\; A/{\textrm}{cm}^2$ at $O_2/Ar{\approx}1/9$.

• Journal of the Korean Ceramic Society
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• v.19 no.4
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• pp.281-286
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• 1982

The composition of glasses to be suitable for crystallisation of $BaTiO_3$ by heat-treatment and the dielectric properties of the glass-ceramics were investigated. The composition of the family of glasses was defined by the formula $\chi$ $BaTiO_3 + (100-$\chi$)Al_2O_3$.$2SiO_2$ and excess BaO. Data were presented on dielectric constant and loss tangent at various frequencies. The effects of excess BaO on dielectric properties were investigated. The additions of $Na_2O$ and $Nb_2O_5$ shifted the Curite temperature of these glass-ceramics. The glass composition which was able to be melted at 145$0^{\circ}C$ and moulded as homogeneous glass phase without devitrification should contain $Al_2O_3$.$2SiO_2$ more than 30 mole %. The more the amount of additive BaO increased, the more dielectric constant increased. When the maximum heat-treatment temperature was 105$0^{\circ}C$, we obtained higher dielectric constant than that of 95$0^{\circ}C$. The dielectric constant and the dielectric loss were stable at frequencies between 5$\times$104 and 107 cycle per second. When $Na_2O$ and $Nb_2O_5$ were added, the Curie temperature, presented at 14$0^{\circ}C$ to 15$0^{\circ}C$, shifted to lower temperature. Therefore, the glass-ceramics having high dielectric constant at room temperature were obtained.