• Journal of the Korean Ceramic Society
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• v.36 no.4
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• pp.343-353
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• 1999

Microwave(2.45 GHz) was used as energy source in hydrothermal reaction to fabricate ultrafine BaTiO3 powder. Using microwave of 700 W, crytal BaTiO3 began to fom after 5 min in microwave-autoclave sys-tem. The crystallinity was not noticeably increased with increasing longer reaction time than 10 min. On the other hand in microwave-reflux system crytal BaTiO3 began to form after 15min and the crystallinity was not noticeably increased with increasing longer reaction time than 1hr,. In either case particle size dis-tribution was considerably uniform due to the effect of homogeneous heating by microwave. In addition mi-crowave heating gave an extremely small degree of particle agglomeration compared to electric heating. Av-erage sizes of as-synthesized powders were 30-60nm. Ba/Ti ratio in sol played an important role in det-ermining the particle size. It seems that excess barium forms different phases such as Ba(OH)2 which makes thin layer on the surface of BaTiO3 powder. This thin layer would inhibit the agglomeration of Ba-TiO3 powders and keep the small grain size. In microwave-autoclave system tetragonal-BaTiO3 was formed directly by the reaction of only 15 min. In the case of microwave-reflux system tetragonal-BaTiO3 was formed by driyng over 25$0^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.314-314
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• 2011

Using first principles calculations, we investigated the interface structure effects on the magnetic properties of the Fe/BaTiO3 system. On the BaO-terminated surface, a Fe monolayer is formed as two Fe atoms are adsorbed on the top sites of Ba and O in the ($1{\times}1$) surface unit and a Fe ML is formed on the TiO2-terminated surface as two Fe atoms are adsorbed on the two O top sites. The magnetic anisotropy energy of Fe was higher on the TiO2?-erminated surface (1.5 eV) than on the BaO-terminated surface (0.5 eV). The decomposed electron density of the states showed that the stronger hybridization of Fe with the TiO2 layer than with the BaO layer is the most important reason for the higher magnetic anisotropy energy.

• Journal of Integrative Natural Science
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• v.1 no.2
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• pp.84-88
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• 2008

The formation and thermal properties of the $BaO_2$ and $TiO_2$ mixtures were prepared by mechanical alloying method was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). The rotating speed of 750 rpm shows more effects on the formation of $BaTiO_3$ single phase. The internal strain calculated using Williamson-Hall method was $4.27{\times}10^{-3}$ for the mixture milled for 300 min, the crystallite size was calculated using the Scherrer method decreased with milling time. The $BaTiO_3$ crystal improved crystallinity was formed by thermal annealing at a temperature of $600^{\circ}C$ for 1 h for the mixture milled for 300 min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.400-403
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• 2004

The dielectric properties of $BaTiO_3/SrTiO_3$ multilayered thick films with printing times were investigated. $BaTiO_3/SrTiO_3$ thick films were deposited by Screen-printing method on alumina substrates. The obtained films were sintered at $1400^{\circ}C$ with bottom electrode(Pt) for 2hours. The structural and the dielectric properties were investigated for various printing times. The BST phase appeared in all of the $BaTiO_3/SrTiO_3$ mutilayered thick films. The $BaTiO_3/SrTiO_3$ multilayered thick film thickness, obtained by one printings, was $50{\mu}m$. The dielectric constant and dielectric loss of the $BaTiO_3/SrTiO_3$ multilayered thick film, obtained by five printings, were about 266, 0.8% at 1Mhz, respectively.

• Journal of the Korean Ceramic Society
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• v.26 no.4
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• pp.493-498
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• 1989

High purity, submicron BaTiO3 powder was prepared by a hydrothermal technique using Ba(OH)2.8H2O, TiCl4 and NH4OH as starting raw materials. The submicron BaTiO3 powder was synthesized at 130~23$0^{\circ}C$ for 2.5h to yield highly crystalline particles with a narrow particle distribution. The mole ratio of Ba(OH)2.8H2O/TiO(OH)2 was 1.5. It is possible to obtain BaTiO3 with Ba : Ti=1.00$\pm$0/01. The samples densified well at 13$25^{\circ}C$, showing a uniform and fine grain structure. The grain size ranged between 0.3 and 0.5${\mu}{\textrm}{m}$. The products obtained by hydrothermal treatment at various temperatures from 130 to 23$0^{\circ}C$ were characterized by XRD, DTA, BET and SEM etc.

• Journal of the Korean Ceramic Society
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• v.33 no.7
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• pp.743-754
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• 1996

In this study (Ba1-xPbx)TiO3 was synthesized by modified oxalate process in order to prevent vaporization of PbO through low temperature synthesis climinate Cl ion reproducibly substitute Pb for by and uniformly distribute ion (Ba1-xPbx)TiO3 was synthesized by coprecipitation of lead acetate barium acetate and ammonium titanyl oxalate have been used as starting materials. The substitution of Pb for Ba was reproducibly possible synthetic temperature of perovskite structure becomes lowed as the Pb concentration increases and fine partic-les (specific surface are :7.2 cm2/g) were obtained, BaTiO3 powders calcined at 90$0^{\circ}C$ for 3 hours were cubic from in XRD analysis and as Pb content was increases evident split of tetragonal peaks could be observed The optimum conditions to synthesize (Ba,Pb)TiO3 powder are the followings ; synthesis temperature (5$^{\circ}C$)

• Journal of the Korean Ceramic Society
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• v.24 no.1
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• pp.41-46
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• 1987

When barium titanate was synthesized in soild-solid reaction the abnormal expansion occurred from 900$^{\circ}C$ to 1100$^{\circ}C$. The equi-molecular mixture of BaCO3 and TiO2 was sintered from 800$^{\circ}C$ to 1300$^{\circ}C$ on the condition of air, vacuum and CO2 atmosphere. After that the specimens were tested closely with XRD, Dilatometer, SEM and EDS. The result indicated that; 1. The crystal phase which was concerned with expansion of BaTiO3 was Ba2TiO4 as the intermediate crystal phase. 2. The formation of Ba2TiO4 was affected by the firing atmosphere. 3. The expansion occurred when BaTiO3 changed to Ba2TiO4 and pore also expanded by the expansion of BaTiO3 body just as the model of expansion.

• Journal of the Korean Ceramic Society
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• v.26 no.3
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• pp.371-380
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• 1989

The purpose of this experiment is to elucidate the reaction mechanism concerning to the formation of crystalline BaTiO3 synthesized by adding the pH control agent(KOH soln) in TiCl4 and BaCl2 solution (Wet direct synthetic method). In this expeirment, it is identified that the amorphous barium-titanate having Ba-O-Ti bonding is formed above pH5 due to the -OH- ion and Ti-gel is formed below pH5 due to the polymerization of metatitanic acid. The bonding of the amorphous Ba-O-Ti is identified by FT-IR spectrum and crystallization temperature is about 82$0^{\circ}C$. If the pH of the above system according to the -OH- ion concentration is above 13.8, the polymerized metatitanic acid will be depolymerized and produce [TiO3]2+ion and crystalline BaTiO3 is formed by reacting the produced [TiO3]-- ion with the active Ba++ ion.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.311-312
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• 2007

In this study, composite $BaSrTiO_3$ has been studied for high frequency device applications. Composite $Ba_{0.5}Sr_{0.5}TiO_3$ has high dielectric permittivity and low loss tangent at the relative frequency range from MHz to GHz. 10,30 and 50 wt% of epoxy doped $Ba_{0.5}Sr_{0.5}TiO_3$ powders were prepared with bisphenol A and F polymer employing ball milling process. Epoxy/($BaSrTiO_3$) composites thick films were screen printed on the Cu plated PCB substrates through screen printing methods. The specimens were designed for the embedded capacitor applications. Temperature dependent dielectric permittivity of Epoxy doped $BaSrTiO_3$ ceramics was measured.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.224-225
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• 2006

$BaTiO_3$ powder를 epoxy/solvent에 혼합한 슬러리와 solvent에 혼합한 슬러리의 분산 특성을 평가하기 위하여 분산제인 silane을 $BaTiO_3$ powder 표면에 코팅한 powder를 이용하여 분산실험을 진행하였다. Silane 표면 코팅 량에 따른 $BaTiO_3$ 슬러리와 $BaTiO_3$/epoxy 복합 슬러리의 분산 특성은 서로 다른 경향으로 나타남을 확인하였으며, silanae 최적 첨가량은 $BaTiO_3$/solvent 슬러리의 경우 0.3~0.5 wt%, $BaTiO_3$/epoxy/solvent 슬러리의 경우 1wt% 이상 첨가한 조건이었다. 또한 분산성 측정의 방법으로 점도 측정 방법과 함께 표면 거칠기 측정 방법의 가능성을 확인하였다.