• Proceedings of the Korean Ceranic Society Conference
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• 2003.10a
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• pp.189.2-189
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• 2003

• Journal of Powder Materials
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• v.16 no.1
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• pp.37-42
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• 2009

In this study, the feasible test for the mechanical property characterization of $BaTiO_3$ ceramics and multi-layer ceramic capacitor(MLCC) was performed with nanoindentation technique. In case of $BaTiO_3$ ceramics, hardness and elastic modulus are dependent on the densification of specimen showing the highest hardness and elastic modulus values of 12.3 GPa and 155 GPa, respectively at $1260^{\circ}C$. In case of MLCC chip, hardness of dielectric layer was lower than that of margin region. The nanoindentation method could be useful tool for the measurement of mechanical property within $BaTiO_3$ dielectric layer of very thin thickness in high capacitance MLCC.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.359-364
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• 1991

The effects of Pb5Ge3O11 on the sinterbility and lattice variation of the semiconducting 0.15 mol% Y2O3 doped BaTiO3 have been investigated as functions of additive contents (from 0.25 mol% to 2.5 mol%) and sintering temperatures (from 110$0^{\circ}C$ to 130$0^{\circ}C$). As the amount of Pb5Ge3O11 increases, the sinterbility of BaTiO3 increases abruptly at around 115$0^{\circ}C$. During the sintering, the most of Pb+2 ions in additives penetrate into BaTiO3 lattices and Ge+4 ions present at grain boundaries. Therefore the c lattice of the BaTiO3 increases largely and then the tetragonality increases due to the diffusion of the Pb+2 ions.

• Journal of the Korean Ceramic Society
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• v.31 no.10
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• pp.1240-1246
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• 1994

While sintering the Pb(Mg1/3Nb2/3)O3-PbTiO3-BaTiO3 system through solid-reaction route, pyrochlore(Pb3Nb4O13) phase while reduces the dielectric constant is inevitably formed. Substitution of Pb(Mg1/3Nb2/3)O3 with PbTiO3 and BaTiO3 can retard the occurrence of pyrochlore phase. The perovskite solid-solution without containing pyrochlore phase can be obtained when we consolidated the materials consisting of PbTiO3 and BaTiO3 at 1200℃ for 2 hours. The sintered body composed of 0.8Pb(Mg1/3Nb2/3)O3-0.1PbTiO3-0.1BaTiO3 composition showed the diffused phase transition(DPT) phenomena and the maximum value of dielectric constant at 0℃ (Tc') with the value of 1.3×104.

• Journal of the Korean Ceramic Society
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• v.28 no.9
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• pp.661-666
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• 1991

Microstructure, room temperature resistivity and temperature coefficient of resistance of BaTiO3 ceramics were studied by varying cooling rates and additives such as TiO2, SiO2 and Al2O3. The basic composition of the BaTiO3 ceramics was formed by adding 0.25 mol% Dy2O3 and 0.07 mol% MnO2 to the BaTiO3 composition. Unlike the additives of SiO2 and Al2O3, an addition of 2 mol% TiO2 to the basic composition was effective to control the grain size of the fired specimens. The room temperature resistivity and the temperature coefficient of resistance for the specimen of this particular compostion were measured as about 102 ohm.cm and 16.5%/$^{\circ}C$, respectively. The observed grain boundary phase of the sample with Al2O3 additive was BaTi3O7, while that of the samples with SiO2 additive was confirmed as BaTiSiO5.

• Journal of the Korean Ceramic Society
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• v.46 no.2
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• pp.189-199
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• 2009

The Powder characteristics and sintering behavior of $SiO_2$ coated $BaTiO_3$ were studied. $BaTiO_3$ powders were synthesized by the liquid mix method developed by Pechini, and silica coating was prepared by alkoxide hydrolysis method with TEOS and ethanol. The particle size of the $BaTiO_3$ powders was 35 nm and the thickness of the $SiO_2$ coating layer was 5 nm. As the $SiO_2$ content increased, the $SiO_2$ layers improved the powder dispersion by increasing electrostatic repulsion between the $BaTiO_3$ particles. Effects of MgO coating on microstructure and dielectric properties of $BaTiO_3$ have been studied compared with mechanically MgO mixed $BaTiO_3$. MgO coated $BaTiO_3$ particles were prepared by a homogeneous precipitation method using $MgCl_2\cdot 6H_2O$ and urea. MgO coated $BaTiO_3$ exhibited homogeneous microstructure compared with mixed samples. XRD analysis revealed that Mg substitution for the Ti site in the MgO mixed sample was much greater than in the coated one. Electrical properties of MgO mixed and coated $BaTiO_3$ were affected by the diffusion behavior of Mg in $BaTiO_3$ lattice.

• Korean Journal of Materials Research
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• v.18 no.9
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• pp.475-481
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• 2008

Positive temperature coefficient of resistivity (PTCR) characteristics of (1-x)$BaTiO_3-x(Bi_{0.5}K_{0.5})TiO_3$ ceramics doped with $Nb_2O_5$ were investigated in order to develop the Pb-free PTC thermistor available at high temperatures of > $120^{\circ}C$. The PTCR characteristics appearing in the ($B_{i0.5}K_{i0.5})TiO_3$ (< 5 mol%) incorporated $BaTiO_3$ ceramics, which might be mainly due to $Bi^{+3}$ ions substituting for $Ba^{+2}$ sites. The 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics showed good PTCR characteristics of a low resistivity at room temperature (${\rho}_r$) of $31{\Omega}{\cdot}cm$ a high ${\rho}_{max}/{\rho}_{min}$ ratio of $5.38{\times}10^3$, and a high resistivity temperature factor (${\alpha}$) of $17.8%/^{\circ}C$. The addition of $Nb_2O_5$ to 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics further improved the PTCR characteristics. Especially, 0.025 mol% $Nb_2O_5$ doped 0.99$BaTiO_3-0.01(Bi_{0.5}K_{0.5})TiO_3$ ceramics exhibited a significantly increased ${\rho}_{max}/{\rho}_{min}$ ratio of $8.7{\times}10^3$ and a high ${\alpha}$ of $18.6%/^{\circ}C$, along with a high $T_c$ of $148^{\circ}C$ despite a slightly increased ${\rho}_r$ of $31{\Omega}{\cdot}cm$.

• Journal of the Korean Ceramic Society
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• v.27 no.6
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• pp.741-746
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• 1990

Dielectrics which do not lose their high insulation resistance in reducing atmosphere are necessary for multilayer ceramic capacitors with Ni internal electrode. In this study we investigated the Ca ion site occupancy in A-site excess Ca-doped BaTiO3 by measuring the insulation resistance, lattice constant and Curie temperature. Its Curie temperature, which was lower than that of the pure BaTiO3, was more lowered by sintering in reducing atmosphere. Lattice constnat of c-axis decreased and that of a-axis increased, suggesting substitution of Ca ions for Ti ions. Hence CaTi" acts as an acceptor to maintain high insulation resistance.ance.

• Journal of the Korean Ceramic Society
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• v.22 no.5
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• pp.29-34
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• 1985

The PTCR characteristics of the $BaTiO_3$ as a function of the molten KCl and dopant $Sb_2O_3$ were investitated. When the weight ratio of KCl to raw materials was above 0.1, $BaTiO_3$ was synthesized by calcining at 80$0^{\circ}C$ for 6 hrs. As the amount of the KCl increased the resistivity of the $BaTiO_3$ at room temperature incr-eased. This can be explained by charge compensation effect between electrons and holes and with microstruc-tures change of the specimens. The resistivity of the $BaTiO_3$ decreased with increasing amount of $Sb_2O_3$. In the time-current characteristics initial current decreased with increasing the ratio of KCl to raw materials but initial current increased and then decreased with the increase of the dopant $Sb_2O_3$. These results of the time-current characteristics can be explained by the resistivity-temperature characteristics.

• 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.