• Journal of the Korean Ceramic Society
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• v.39 no.7
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• pp.628-634
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• 2002

Formation rate of tetragonal BaTiO$_3$powder by hydrothermal synthesis and its dielectric property were studied. Submicron tetragonal BaTiO$_3$ powders were prepared hydrothermally, using Ba(OH)$_2$.8$H_2O$, TiO$_2$(anatase) and KOH as starting chemicals. Characterization via X-ray diffractometry, field emission scanning electron microscopy confirmed that increasing calcination temperatures(from 1100 to 130$0^{\circ}C$) promotes the formation of tetragonal BaTiO$_3$. Tetragonal BaTiO$_3$ ceramics, obtained by calcining at 1200 for 3 h after hydrothermal synthesis at 200 for 168 h, exhibited submicron size of 0.5 ~ 0.7 ${\mu}{\textrm}{m}$ and high relative permittivity.

• Journal of the Korean Ceramic Society
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• v.42 no.2 s.273
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• pp.81-87
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• 2005

The compositions for LTCC embedded capacitors based on $BaTiO_3$ ceramics with $5\~15\;wt\%$ of lithium-borosilicate glass frits were studied. After the glass frits, which is chemically stable and has acceptable ability of low-temperature sintering, were added to the host dielectric materials, the sintering behavior and dielectric properties were evaluated. As for $BaTiO_3$, relative density of >$95\%$, permittivity 990, and dielectric loss $3.1\%$ were obtained when sintered at $925^{\circ}C$ with 5 wt$\%$ of glass frits. As for $(Ba,Ca)(Ti,Zr)O_3$ ceramics, relative density of >$95\%$, open porosity <$0.5\%$, permittivity 700, and dielectric loss $2\%$ were obtained when sintered at $875^{\circ}C$ with 10 wt$\%$ of glass frits.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1993.11a
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• pp.25-28
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• 1993

In this study, the dielectric properties of (Sr$\sub$1-x/Ca$\sub$x/)TiO$_3$+yNb$_2$O$\sub$5/(0.1 x 0.3, 0.004 y 0.008) ceramic capacitor were investigated. The specimen was sintered for 3hr at 1350$^{\circ}C$ in gas(N$_2$) atmosphere. The reduced specimen fared at 1200$^{\circ}C$ in air. The used specimens had the apparent permittivity of 3${\times}$10$^4$∼4${\times}$10$\^$5/, tan$\delta$ of 0.05 -0.2, and insulating resistance of 10$\sub$9/∼10$\^$12/ $\Omega$.cm. The specimens had the stable temperature coefficient of capacitance.

• Journal of the Korean Ceramic Society
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• v.45 no.5
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• pp.263-267
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• 2008

$(Bi_{1/2}Na_{1/2})TiO_3$-based ceramics have been intensively studied as lead-free piezoelectric ceramics. In this study, the piezoelectric properties and phase transition behaviors of BNT based solid solution $(Bi_{0.5}Na_{0.5})_{1-x}Ca_xTiO_3$ ($X=0.01{\sim}0.25$) were investigated. The morphotropic phase boundary(MPB) zone which BNT is transformed from rhombohedral to cubic structure was appeared by adding $CaTiO_3$ with 0.12 mol by the measurement of permittivity and X-ray diffraction. The behavior which ferroelectric BNT with adding $CaTiO_3$ was changed to antiferroelectric and paraelectric state was confirmed by the measurement ofhysterisis loop and depolarization temperature as a function of temperature. As $CaTiO_3$ concentration was increased, the phase transition temperature was decreased. The piezoelectric properties were highest at 0.01 mol of $CaTiO_3$ concentration. The electromechanical coupling factor($K_t$) and mechanical quality factor($Q_m$) were 42% and 254, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.238-239
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• 2005

The effects of $Li_2CO_3$ addition on the sintering behavior of $Ba_{0.5}Sr_{0.5}TiO_3$ ceramic have been investigated. The amount of $Li_2CO_3$ was varied from 1 wt% to 5 wt%. The crystalline and dielectric properties were investigated through X-ray diffraction and frequency dependent permittivity, respectively.

• Polymer(Korea)
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• v.33 no.3
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• pp.224-229
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• 2009

The dielectric properties of semi-IPN poly(phenylene oxide)(PPO) blend/$BaTiO_3$(BT) composites are investigated. The composites are fabricated via melt-mixing of crosslinker and peroxide in precursor PPO composite obtained by precipitating the suspension consisted of PPO, BT and toluene into methylethyl ketone, poor solvent of PPO. The permittivity of the precursor PPO composites shows higher value than that of integral-blended PPO composites by extruder and coincides with the theoretical value calculated by logarithmic rule of mixture. The blend of PPO and cross-linked triallyl isocyanurate is most effective for lowering the permittivity and loss tangent owing to the suppression of the orientation polarization of matrix. In contrast, 4,4'-(1,3-phenylene diisopropylidene) bisaniline, which has amine unit in its structure, increases the permittivity as well as loss tangent of the composite, but it has the ability to densify the matrix resin and the interfacial adhesion between the matrix and filler to improves flexural strength and modulus.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.525-530
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• 2011

We investigated the electrical properties the starting material and sintering condition on the laminated PTC thermistor for micro circuit protection. The influences of $BaTiO_3$ powder with the 0.3 and 0.45 ${\mu}m$ size and the electrical characteristics (Ba,Sr)$TiO_3$ sintered at 1350~1400$^{\circ}C$ for 2 h in a reducing atmosphere (1% $H_2/N_2$). The sintered (Ba,Sr)$TiO_3$ was increased pore and the grain size was decreased according to increasing Sr additions. In relative permittivity, the phase transition temperature of (Ba,Sr)$TiO_3$ was decreased for 2.5$^{\circ}C$ according to increasing 0.01 mole Sr additions, and the phase transition dose not appeared about 0.3 mole Sr addition. The (Ba,Sr)$TiO_3$ was show the low resistance from 0.01 mole to 0.05 mole by Sr addition, regardless of sintering temperature. The (Ba,Sr)$TiO_3$ was show $10^2$ jump order at 0.1 and 0.2 mole Sr addition, and PTCR of the sintered $(Ba_{0.7}Sr_{0.3})TiO_3$ does not appeared about 0.3 mole Sr addition, regardless of the sintering temperature and starting material size.

• Journal of the Korean Ceramic Society
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• v.41 no.12 s.271
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• pp.915-920
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• 2004

The main phase of $BaTi_{4}O_9$-based ceramics was transformed to $BaTi_{5}O_{11}$ caused by the sintering with borosilicate glass, which was analyzed by using XRD and TEM. We considered that the phase change from $BaTi_{4}O_9$-based ceramics to the Ti-rich $BaTi_{5}O_{11}$ phase resulted from borosilicate glass selective absorbing of Ba ions from the $BaTi_{4}O_9$. In these results, we found a dependence on the amounts of the glass frits and the annealing temperature, and the phase change is also dependent of the main phases of $Ba_{4}Ti_{13}O_{30},\;and\;Ba_{2}Ti_{9}O_{20}$, which are involved in the $BaO-TiO_2-based$ Ti-rich region. In the case of sintering of middle- and high- permittivity material with additional glass frits for middle- and high- dielectric coefficients LTCC composition, control of weight fraction of the glass frits accompanying low-temperature sintering property with appropriate phase change is required.

• Advances in materials Research
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• v.1 no.2
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• pp.115-128
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• 2012

The structural and electrical properties of $(1-x)Ba(Sm_{1/2}Nb_{1/2})O_3-xBaTiO_3$; ($0{\leq}x{\leq}1$) ceramics were prepared by conventional ceramic technique at $1375^{\circ}C$/7 h in air atmosphere. The crystal symmetry, space group and unit cell dimensions were derived from the X-ray diffraction (XRD) data using FullProf software whereas crystallite size and lattice strain were estimated from Williamson-Hall approach. XRD analysis of the compound indicated the formation of a single-phase cubic structure with the space group Pm m. Dielectric study revealed that the compound $0.75Ba(Sm_{1/2}Nb_{1/2})O_3-0.25BaTiO_3$ is having low and ${\varepsilon}^{\prime}$ and ${\varepsilon}^{{\prime}{\prime}}$ a low $T_{CC}$ (< 5%) in the working temperature range (up to+$100^{\circ}C$) which makes this composition suitable for capacitor application and may be designated as 'Stable Low-K' Class I material as per the specifications of the Electronic Industries Association. The correlated barrier hopping model was employed to successfully explain the mechanism of charge transport in the system. The ac conductivity data were used to evaluate the density of states at Fermi level, minimum hopping length and apparent activation energy of the compounds.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1803-1805
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• 1999

The thermal expansion coefficient of the titania-fused silica glass$(TiO_2-SiO_2)$ called KLR-1.1 is known to $0{\pm}0.03$ ppm/K, while that of normal fused-silica glasses is about +0.5 ppm/K at room temperature. To analysis the dielectric properties of the KLR-1.1, the sample with diameter of 30 mm and thinkness of 1 mm is covered with gold film. Its relative permittivity and dissipation factor of KLR-1.1 is evaluated to $4.011{\pm}0.012(1\sigma)$ and $(4.86{\pm}0.02){\times}10^{-4}(1{\sigma})$ at 1 kHz respectively. The measurement techniques used and results are more discussed in this paper.