• 한국세라믹학회지
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• 제35권8호
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• pp.864-870
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• 1998

The effect of {{{{ {{Nb }_{2 }O }_{5 } }} and CoO addition on the temperature dependence of the {{{{ {BaTiO }_{3 } }}-based ceramic capa-citor has been studied. X7R with moderate temperature dependence has been developed by means of pre-cisely controlled {{{{ {{Nb }_{2 }O }_{5 } }}/CoO ratio. Dielectric constant(K) and dissipation factor(DF) were 3500 and 1.5% respectively. As the content of {{{{ {{Nb }_{2 }O }_{5 } }} was increased the curie temperature(Tc) was shifted to lower tem-perature and the dielectric constant at Tc was decreased. The proper addition of CoO with {{{{ {{Nb }_{2 }O }_{5 } }} improved the temperature dependence of dielectric properties of the {{{{ {BaTiO }_{3 } }}-based ceramic capacitor.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.12-12
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• 2009

We weal know that PbO was poisonous and prone to volatilize, then to pollute the circumstance and hurt to people, so we should dope other innocuous additives instead of lead to increase Tc of composite PTC material. In order to prepare lead-free $BaTiO_3$-based PTC with middle Curie point, the incorporation on $(BaNaK)(TiNb)O_3$ into $BaTiO_3$-based ceramics was investigated on samples containing 0.05, 0.07 and 0.1mol% of $(BaNaK)(TiNb)O_3$. $(BaNaK)(TiNb)O_3$ was compounded as standby material by conventional solid-state reaction technique. The starting materials were $Na_2O_3$,$K_2CO_3$, $BaCO_3$, $TiO_2$ and $Nb_2O_5$ powder, and using solid-state reaction method, too. The microstructure of samples were investigated by SEM, DSC, XRD and dielectric properties. Phase composition and lattice parameters were investigated by X-ray diffraction. Also, we are measure the resistivity of sintered bodies with calcinations condition.

• 한국세라믹학회지
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• 제31권10호
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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.

• 한국세라믹학회지
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• 제24권6호
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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.

• 한국표면공학회지
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• 제54권4호
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• pp.178-183
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• 2021

The temperature and frequency dependence of the dielectric constant of the BaTiO₃ substituted with two types of donor dopants, Nb⁵⁺ and Ta⁵⁺, respectively, were compared and analyzed. Dielectric specimens of four specific compositions, Ba_0.95Nb_0.05TiO₃, Ba_0.90Nb_0.10TiO₃, Ba_0.95Ta_0.05TiO₃, and Ba_0.90Ta_0.010TiO₃ were prepared by calcining at 1100 ℃ and sintering at 1300 ℃ to have a perovskite structure to measure capacitance. XRD and SEM analysis were used to observe the structure, with particular focus on the integration into the Nb⁵⁺ and Ta⁵⁺ substituted BaTiO₃ crystal lattice. X-ray diffraction peaks in the (200) and (002) planes were observed between 45.10° and 45.45° of the BaTiO₃ solid solution substituted with different fractions of Nb⁵⁺ and Ta⁵⁺. The dielectric properties were analyzed and the relationship between the properties and structure of the substituted BaTiO₃ was established. The fine particles and high density of the substituted BaTiO₃ were maintained like pure BaTiO₃, and in particular, a shift toward the low temperature side of the phase transition temperature range was clearly found, unlike pure BaTiO₃. In addition, the phase transition at a temperature higher than the Curie temperature relatively satisfies the modified Curie-Weiss law.

• 한국전기전자재료학회논문지
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• 제22권3호
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• pp.205-209
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• 2009

In this study, in order to develop the composition ceramics for lead-free ultrasonic motor, (1-x-0.09)$NaNbO_{3-x}BaTiO_3-0,09LiNbO_3$ ceramics were fabricated using a conventional mixed oxide process and their piezoelectric and dielectric characteristics were investigated according to the $BaTiO_3$ substitution. All the specimens showed orthorhombic phase structure without secondary phase, $BaTiO_3$ substitution enhanced density, dielectric constant(${\epsilon}_r$) and electromechanical coupling factor($k_p$), However, mechanical quality factor was deteriorated. Curie temperature of specimens was observed as about $380^{\circ}C$. At the $BaTiO_3$ substitution of 4 mol%, density, electromechanical coupling factor($k_p$), dielectric constant(${\epsilon}_r$) and piezoelectric constant($d_{33}$) of specimen showed the optimum value of $4.493g/cm^3$, 0.236, 175, 70 pC/N, respectively.

• 한국세라믹학회지
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• 제25권6호
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• pp.639-644
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• 1988

The physical and dielectric properties of complex perovskite compound Sr(Mg1/3Nb1/3)O3-Ba(Mg1/3Nb2/3)O3-Ba(Mg1/3Ta2/3)O3(BMT) system were investigated as a function of composition. As the mole ratio of BMN was increased, lattice parameter ratio c/a was slightly increased, and density was increased in SMN-BMN system. However, in BMN-BMT system, lattice parameter ratio c/a and density were decreased with increasing the mole ratio of BMN. Dielectric constant, dielectric loss at $25^{\circ}C$ and 100kHz, and temperature coefficient of resonant frequency, the dependence of temperature in capacitance were increased with increasing the mole ratio of BMN in SMN-BMN-BMT system. These result can be explained according to the degree of order=disorder and dielectric constant.

• 대한전기학회논문지
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• 제44권5호
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• pp.644-648
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• 1995

Transparent xBa(La$_{1}$2/Nb$_{1}$2/)O$_{3}$-(1-x)Pb(Zr, Ti)O$_{3}$ (x=8.5, 9.0[mol.%], Zr/Ti=70/30~40/60) ceramics were fabricated by the two-stage sintering method, the electrooptic properties were investigated with Ba(La$_{1}$2/Nb$_{1}$2/)O$_{3}$ content and Zr/Ti composition ratio. Decreasing the Zr/Ti ratio, the electrooptic property was changed from a quadratic electrooptic effect to a linear electrooptic effcet. In the BLN-PZT 9.0/50/50 specimen having the tetragonal structure, the linear electrooptic coefficient had the highest value of 6.01*10$^{-10}$ [m/V] and in the BLN-PZT 9.0/55/45 specimen which located near the MPB region, the quadratic electrooptic coefficient had the highest value of 10.53*10$^{-16}$ [m$^{2}$/V$^{2}$].

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 추계학술대회 논문집
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• pp.248-251
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• 1999

The microwave dielectric properties of The Dielectric Properties of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$ (A = Sr, Ca, x = 0, 0.2 ,0.4 ,0.6, 0.8, 1.0) were investigated. In composition of $Ba_{1-x}$A$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O, densities are decreased with increasing x values. Grain sizes are decreased with Sr content and Increased with Ca content. The hexagonally ordered superstructure was observed in $Ba_{1-x}$Sr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the intensity of superlattice increased with x value. In $Ba_{1-x}$Cr$_{x}$(Mg$_{1}$3/Nb$_{2}$3/)O$_3$(BSMN) systems, the additional diffraction patterns were shown. The highest value of $\varepsilon$$_{r}$ was shown in x=0.2 of BCMN systems and the value was 41.9. The highest Q$\times$f was shown in x=0.2 of BSMN systems and the value was 68,000. $\tau$$_{f}$ were shown 0 ppm/$^{\circ}C$ near x=0.8.TEX> near x=0.8.0.8.

• E2M - 전기 전자와 첨단 소재
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• 제3권3호
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• pp.233-241
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• 1990

본 연구에서는 xPb(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-yBa(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$-zPbTiO(0.50.leq.x.leq.0.60, 0.10.leq.y.leq.0.20, 0.20.leq.z.leq.0.40)세라믹을 1050.deg.C에서 2시간동안 유지시켜 일반소성법으로 제작하였다. 시편 제작시 조성은 조성변태 상경계부근을 선택하였으며 Ba(Zn$_{1}$3/ Nb$_{2}$3/)O$_{3}$ 고용량에 따른 purochlore상의 억제 및 그 영향을 조사하고 구조적, 유전적 및 압전적 특성을 측정하였다. X-선 회절분석 및 미세구조의 관찰 결과, Ba(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$의 고용량에 따라 pyrochlore상 및 미반응 물질등은 억제되어 0.20mol 고용된 시편에서는 균질한 perovskite상이 형성되었다. Ba(Zn$_{1}$3/Nb$_{2}$3/)O$_{3}$의 고용량이 증가함에 따라 유전상수는 증가하여 0.50PZN-0.20BZN-0.30PT시편의 경우 6880.9의 높은 값을 나타내었으며 정전용량의 온도계수는 감소하여 0.383[%/.deg.C]의 양호한 값을 나타내었다. 큐리온도는 PbTiO$_{3}$의 고용량이 0.20mol에서 0.40mol로 증가함에 따라 30.deg.C에서 170.deg.C로 증가하였다. 전기기계 결합계수 (K$_{p}$), 기계적 품질계수(Qm) 및 압전전하 계수 (d$_{33}$)는 조성변태 상경계 부근의 조성에서 크게 나타났으며 0.60PZN-0.15BZN-0.25PT 시편의 경우 각각 58.5%, 120.5, 150x$10^{-12}$[C/N]의 값을 나타내었다.다.다.