• Journal of the Korean Ceramic Society
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• v.33 no.2
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• pp.214-222
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• 1996

The effect of physicochemical properties of organic solvent and dispersant among organic solvent dispersant binder and plasticizer which are used as processing additives in MLCC fabrication process on the dispersion of BaTiO3 was studied. The steric and electrostatic stabilization mechanisms in dispersion of BaTiO3 in organic media were evaluated respectively. The sttability of BaTiO3 achieved bysteric stabilization was dependent on the fraction of surface coverage of dispersant adsorption on BaTiO3. The electrostatic repulsive forces of BaTiO3 particles dispersed in orgainc media was found to be appreciabley great and dependent mainly on the kinds of organic solvent used. The mechanism affecting the stability of BaTiO3 was studied by the method of rheologi-cal behaviors of BaTiO3 suspension.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.44 no.8
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• pp.1068-1074
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• 1995

Effect of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ addition on the phase changes and microwave dielectric properties of BaTi $O_{3}$-3Ti $O_{2}$ ceramics were investigated. Addition of (Zn$_{1}$3/Nb$_{2}$3/) $O_{2}$ to BaTi $O_{3}$-3Ti $O_{2}$ resulted in the formation of Ba $Ti_{4}$$O_{9}$, $Ba_{2}$ $Ti_{9}$ $O_{20}$, Ba(Zn$_{1}$3/Nb$_{2}$3/) $O_{3}$, and Ti $O_{2}$ phases. Ba $Ti_{4}$$O_{9}$ phase was gradually transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$. This was identified by XRD and microstructure. As the Ba $Ti_{4}$$O_{9}$ phase transformed to $Ba_{2}$ $Ti_{9}$ $O_{20}$ phase, the dielectric constant increased to 37.5. Q*f$_{o}$ value was 40000 at x=0.04, and the temperature coefficient of resonant frequency was +10ppm/.deg. C.C.. C.C.

• Journal of the Korean Ceramic Society
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• v.32 no.4
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• pp.448-454
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• 1995

The effect of WO3 addition on microwave dielectric properties of BaTiO3-3{(1-x)TiO2-xWO3} system was studied. Addition of WO3 to this system resulted in the formation of BaWO4 and Ba2Ti9O20 phases. Both the dielectric constant (K) and the temperature coefficientof resonant frequency (Tf) were decreased with the amount of WO3 addition. The value of Q$\times$f0 was increased as the amount of WO3 was increased up to x=0.0275, and then decreased when x exceeded 0.03. At x=0.0275, this ceramic showed excellent microwave proprties of K=34-35, Q$\times$f0=50,000-53,000, and near zero ppm/$^{\circ}C$ of Tf.

• Journal of the Korean Ceramic Society
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• v.22 no.4
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• pp.61-65
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• 1985

$BaTiO_3$ powders doped with $BaTiO_3$ and $Nb_2O_5$ at 9$0^{\circ}C$ for 1hr. were synthesized by Direct Wet Process. These powders were very homogeneous and fine particle size. To obtain the highe PTCR effect AST($1/3Al_2O_3$.$3/4SiO_2$.$1/4TiO_2$) and $MnO_2$ were added in the semiconduc-ting $BaTiO_3$. In this case $Bi_2O_3$ and $MnO_2$ were used in the form of $Bi(NO)_3$ and $MnCl_2$.$4H_2O$ solution for Direct Wet Process. $BaTiO_3$ doped Nb2O5 and $MnO_2$ demostrated greater PTCR effect than $BaTiO_3$ doped $Nn_2O_5$ only.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.335-338
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• 1998

The effect of glass flit addition on microwave dielectric properties of BaTiO$_3$-3TiO$_2$ ceramic was studied. Addition of glass frit to this system obtained sintered sample below sintering temperature 105$0^{\circ}C$. At BaTiO$_3$-3TiO$_2$+ g1ass frit 3wt% + BaWO$_4$6 wt%m, this ceramic showed excellent microwave properties of dielectric constant 34, Q$\times$f 8,100, temperature coefficient of resonant frequency 4 ppm/$^{\circ}C$ .

• Journal of the Korean Ceramic Society
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• v.35 no.11
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• pp.1130-1140
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• 1998

Thin films of $Bi_4Ti_3O_{12}\;nBaTiO_3(n=1&2)$ were prepared using sols erived Ba-Bi-Ti complex alkoxides. The sols were spin-cast onto $Pt/Ti/SiO_2/Si$ substrates and followed by pyrolysis for 1 hr at $620^{\circ}C,\;700^{\circ}C\;and\;750^{\circ}C$ In the thin films a pyrochlore phase seemed to be formed at a lower temperature and then tran-formed to the layered perovskite phase as the heating temperature increased. In the thin films pyrolyzed at formed to the layered perovskte phase as the heating temperature increased. In the films pyrolyzed at $750^{\circ}C$ the amount of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ reached to 94% while $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ was 77% in composition. This result shows that the formation of the layered pervoskite phase becomes difficult as the amount of complexing $BaTiO_3$ increases. The microstructures and the electrical properties of the thin films were gen-erally improved with the incease of the heating temperature. However the presence of the pyrochlore phase could not be removed effectively. Our study showed that the electrical properties of $Bi_4Ti_3O_{12}{\cdot}BaTiO_3$ were pronouncedly improved with complexing with BaTiO3 when compared to those of $Bi_4Ti_3O_{12}$ while the presence of the pyrochlore phase was detrimental to the those of $Bi_4Ti_3O_{12}{\cdot}2BaTiO_3$.

• Journal of the Korean Ceramic Society
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• v.24 no.6
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• pp.579-585
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• 1987

The effects of flux KCl and dopant Nb2O5 on the PTCR characteristics of BaTiO3 prepared by molten salt synthesis method have been investigated. As the amount of dopant Nb2O5 is over the solubility limit in BaTiO3, the room-temperature resistivity increases, and the PTCR effect and the grain size decrease. The variation of the amount of flux KCl slightly influences on the room-temperature resistivity, PTCR effect and grain size in Nb2O5 doped BaTiO3, but BaTiO3 ceramics prepared by the method of molten salt synthesis show larger PTCR effect than those of conventional calcining of mixed oxides.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.6
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• pp.495-500
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• 2009

The ceramic($BaTiO_3$)-polymer(epoxy) composites have been widely investigated as dielectric materials for embedded capacitors in printed circuit boards (PCBs). The dielectric properties of $BaTiO_3$/epoxy composites prepared using the agglomerated $BaTiO_3$ particles were investigated in the present study. The dielectric constants of the composites prepared using the agglomerated $BaTiO_3$ particles were about 2 times higher than those of the composites with the dispersed $BaTiO_3$ particles. The insulation resistance of the composites prepared using the agglomerated $BaTiO_3$ particles were lower than those of the composites with dispersed $BaTiO_3$ particles. As a result, there is tradeoff between high dielectric constant and insulation resistance in the $BaTiO_3$/epoxy composites. So it is important to select proper agglomerated or dispersed $BaTiO_3$ particles in accordance with needs.

• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.1023-1028
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• 1993

To obtain a single phase of Ba2Ti9O20 at lower temperature than previious other researches. We investigated the effect of Zr substitution for predetermined portions of Ti in Ba2Ti9O20. In this study, the four compounds(x=0, 0.028, 0.048, 0.068) of Ba2(Ti1-xZrx)9O20 were prepared by coprecipitation reaction of BaCl2, TiCl4 and ZrOCl2 with (NH4)2CO3 and NH4OH as the coprecipitating agents and pH regulators, in queous solution. Owing to 4.8 mol% addition, the single phase of Ba2Ti9O20 showing high Q was obtained at 115$0^{\circ}C$ which is lower by 25$0^{\circ}C$ than the temperature in case of mechanical mixtures of BaCO3 and TiO2.

• Journal of the Korean Ceramic Society
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• v.26 no.6
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• pp.783-788
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• 1989

The reason of abnormal expansion in BaTiO3 synthesized in the equimolecular mixture and synthesized in Ba-rich region were investigated at the point of crystal and microstructure. The shrinkage and the expansion of the mixtures in BaCO3-TiO2 system were determined by the mass of BaCO3 added to the equimolecular BaCO3 and TiO2, Ba2TiO4 which was much formed and BaTi2O3 were important crystal in the reaction of Ba-rich region. Sintering phenomena of unreacted BaCO3 activity and the secondary phase caused to generate microcracks in the specimens.