• 한국세라믹학회지
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• 제46권2호
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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.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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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.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.289-290
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• 2006

[ $SrTiO_3$ ] is usually added as shifters in order to move the $T_C$ of $BaTiO_3$ to lower temperatures because it is well established that the $T_C$ of $BaTiO_3$ decreases linearly with a solid solution of $Sr^{+2}$ in place of $Ba^{+2}$. It is not fully understood yet, however, how $SrTiO_3$ influences on the peak value of the dielectric constant $(\varepsilon_{max})$ at the $T_C$ of $BaTiO_3$. This research reports the effect of $SrTiO_3$ addition on εmax at the $T_C$ of $BaTiO_3$ ceramics. Based on the chemical composition and the grain size dependence of the dielectric property of $BaTiO_3$ ceramics, functionally graded $(Ba,Sr)TiO_3$ composites were designed and fabricated. Multi-layered $(Ba,Sr)TiO_3$ composites with a compositional gradient of $SrTiO_3$ exhibited a low temperature coefficient and high dielectric constant in a wide temperature range.

• 자연과학논문집
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• 제4권
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• pp.85-93
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• 1991

$BaCO_3$와 $TiO_2$ 등 mole비 혼합물의 고상반응은 $BaCO_3 + TiO_2\longrightarrow$ $BaTiO_3 + CO_2$의 반응식에 따라 $CO_2$ gas가 발생된다. 이 분해과정을 DTA-TG를 사용하여 속도론적으로 고찰하였다. 그 결과는 다음과 같다. 1. $TiO_2$와 공존하는 $BaCO_3$는 순수한 $BaCO_3$보다 낮은 온도에서 분해된다. 그 이유는 생성물의 free energy가 감소되기 때문이다. 2. $BaCO_3$ 분해과정의 속도론적 고찰에 사용되는 식은 Jander's식보다는 Carter's식이 더욱 의미가 있으며 Carter's식에 의해 구해진 분해 활성화 에너지는 42.8Kcal/mol이다.

• 한국세라믹학회지
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• 제21권4호
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• pp.341-348
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• 1984

$BaTiO_3$ and $SrTiO_3$ were mixed with the mole ratio of 35:65， 50:50 and 65:35 and heated at 1100~120$0^{\circ}C$ for 1~64 hours. The dielectrics of $BaTiO_3$-$SrTiO_3$ system were investigated as a function of amount of solid solution formed. The dielectric constant was increased and Curie temperature was shifted to higher temperature with increasing of heating of soaking time for the same composition and heating temperature. This can be explained by the homogeneous distribution of $Ba^{2+}$ and $Sr^{2+}$ ion in the $BaTiO_3$ system. The Curie temperature was shifted to lower temperature with increasing $SrTiO_3$ in the $BaTiO_3$-$SrTiO_3$system because of decreasing the lattice constant.

• ETRI Journal
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• 제18권1호
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• pp.15-27
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• 1996

The effects of $Nd_2O_3$ and $TiO_2$ addition on the microstructures and microwave dielectic properties of $BaO-Nd_2O_3-TiO_2$ system were investigated. $BaNd_2Ti_4O_{12}$ or $BaNd_2Ti_{5}O_{14}$ phases were observed for compositions based on BaO/$Nd_2O_3$ = 1 ratio. The compositions deviated from $BaO/Nd_2O_3=1$ ratio were composed of major phases of $BaNd_2Ti_4O_{12}$ or $BaNd_2Ti_5O_{14}$, and the compound of $Nd_2O_3$ and $TiO_2(Nd_2Ti_2O_7)$ or that of BaO and $TiO_2(BaTi_4O_9)$. The microstructure of ceramic with $BaO{\cdot}Nd_2O_3{\cdot}4TiO_2$ composition varied from spherical grains to needlelike grains with increasing sintering temperature. With increasing $Nd_2O_3$, the optimum sintering temperature with maximum density increased, and the dielectric constant(${\varepsilon}_r$) and quality factor(Q) decreased due to the formation of secondary phases. With increasing $TiO_2$, the optimum sintering temperature and the dielectric constant decreased with increased Q value. And the temperature coefficient of resonant frequency, ${\tau}_f$ shifted toward positive direction. The dielectric ceramics with $BaO/Nd_2O_3=1$ showed Q values of above 2000 and dielectric constants of above 80 at 3GHz.

• 한국세라믹학회지
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• 제26권2호
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• pp.249-257
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• 1989

Dielectric properties and the stability of the perovskite phase in the Pb(Mg1/3Nb2/3)O3 system have been investigated as a function of amount of BaTiO3 and firing temperature. In the specimens fired at 120$0^{\circ}C$, the pyrochlore phase was eliminated by the addition of 10-15m/o BaTiO3 and also the dielectric constant increased. However, the dielectric constant decreased with further addition of BaTiO3 even though no pyrochlore phase was found to be present. The reducing tendency of the pyrochlore phase decreased with lowering the firing temperature in the system of Pb(Mg1/3Nb2/3)O3 with BaTiO3. Dielectric properties in PMN ceramics were affected by the character of the BaTiO3 rather than the pyrochlore phase.

• 공업화학
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• 제9권7호
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• pp.998-1003
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• 1998

$85^{\circ}C$, 0.4 M $Ba(OH)_2$용액내에서 펄스전류파형을 이용하여 Ti전극위에 $BaTiO_3$박막을 전해 합성하였다. 환원전류 밀도 및 환원시간이 증가함에 따라 $BaTiO_3$의 결정성 및 페러데이 효율이 증가하였으며, 이는 표면 및 전기화학적특성 분석에 의하면 환원 전류 인가시에 $H_2O$의 환원에 의하여 전극표면의 pH가 증가함으로서 산화전류에 의하여 형성된 산화막의 구조변화가 빠르게 진행되기 때문으로 추측된다. 그리고 0.1M $H_2SO_4$용액하에서 산화막을 형성시킨 후 $BaTiO_3$형성에 미치는 영향을 분석한 결과, 산화막 두께가 증가함에 따라서 산화막을 통한 $Ti^{+4}$이온의 이동이 어려워지면서 $BaTiO_3$형성이 억제되며, 일정두께이상에서는 산화막 결함부위에서 결정이 형성됨을 알 수 있었다.

• 한국전기전자재료학회논문지
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• 제17권9호
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• pp.953-959
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• 2004

BaTiO$_3$ powder has been applied in so much electronic ceramics. Therefore, as recent, the method to add or coat additive will be needed BaTiO$_3$ powder. As a kind of the method, the coating of BaTiO$_3$ powder was considered. In this study, during BaTiO$_3$ powder was coated by BaTiO$_3$ sol, gelation path was experimented. Standard coating condition was set for homogeneous coating. The phase of the gel was deferent by gelation path. It was confirmed the amorphous gel was made in BaTiO$_3$ phase easily at low temperature. In the amorphous gel, particle growth was shown at 900$^{\circ}C$, because crystallization temperature was low. The optimal ratio of sol and powder was at 10 vol% for the homogeneous coating.

• 한국전기전자재료학회논문지
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• 제17권9호
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• pp.960-966
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• 2004

On the bases of the results from "Additive Coating of BaTiO$_3$ Powder using Sol Coating Method I", experimental condition was defined. Representative additives for BaTiO$_3$, that is to say, Mg, Ca and Mn were experimented. The sources of the metal ion were used by organometal complex. As added it, the stability of BaTiO$_3$ sol was evaluated. Mg and Ca were stable, however, The solubility limit of Mn-ATH was 0.05 mol ratio in Mn-ATH/sol. The solubility limit of Mg ion in BaTiO$_3$ was lower than 2 mol%. From the x Ray diffraction patterns, lattice parameters were different with temperature and additives, because the solubility of metal ion was varied in BaTiO$_3$. The dielectric constant of BaTiO$_3$ powders which coated with the 1.5 mol% Mg and calcined at 1200$^{\circ}C$ was increased with 20%.