• 한국세라믹학회지
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• 제38권10호
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• pp.881-885
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• 2001

Kinetics and mechanisms of intermediate phases formation in $Ba(Mg_{1/3}Ta_{2/3})O_3$, obtained by a solid state reaction were studied. $Ba{Ta_2}{O_6}$ and ${Ba_4}{Ta_2}{O_9}$ as intermediate products were first formed at $700^{\circ}C$. $Ba(Mg_{1/3}Ta_{2/3})O_3$ was appeared at $800^{\circ}C$. Several reactions take place on heating process. $Ba{Ta_2}{O_6}$ is found at the first stage of the reaction, and then $Ba{Ta_2}{O_6}$ or ${Ba_4}{Ta_2}{O_9}$ react with MgO to form $Ba(Mg_{1/3}Ta_{2/3})O_3$. The reaction of $Ba(Mg_{1/3}Ta_{2/3})O_3$ formation does not complete until fired at $1350^{\circ}C$ for 60 min. The kinetics of solid-state reaction between powdered reactants was controlled by diffusion mechanism, and can be explained by the Jander's model for three-dimensional diffusion.

• 한국재료학회:학술대회논문집
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• 한국재료학회 1993년도 추계 학술발표 강연 및 논문 개요집
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• pp.114-114
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• 1993

• 한국재료학회:학술대회논문집
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• 한국재료학회 1993년도 추계 학술발표 강연 및 논문 개요집
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• pp.113-113
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• 1993

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.242-245
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• 1996

The microstructure of $Ba (Zn_{1/3}Ta_{2/3})O_3$ (BZT) was investigated using X-ray diffractometry(XRD) and transmission electron microscopy (TEM). $Ba_{0.5}TaO_3$ and $Ba_3TaO_{5.5}$ (BT) phasses were observed on the surface of the sintered specimen by XRD. Furthermore, a new type of ordering along the [110] direction was found in sintered specimen by the XRD and TEM analysis. The wavelength of ordering was 0.9 nm which is three times larger than the interplanar distance of (110) plane and new type of ordering is considered to be a result of Zn vacancy ordering. The creation of Zn vacancies and formation of BT phases are attributed to the evaporation of volatile ZnO. A new mechanism for ZnO loss is suggested. In this mechanism, only Zn vacancies are created only when the amount of ZnO loss is small and as the amount of ZnO loss increases, BT phases are formed at the same time. A new unit cell of ordered structure is suggested as the superlattics containing three BZT unit cells.

• 한국전기전자재료학회논문지
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• 제14권3호
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• pp.197-201
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• 2001

The microwave dielectric properties of (1-x)Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$-xBa(Co$_{1}$3/Nb$_{2}$3)O$_3$(x=0.25~0.5) ceramics depending on the Ba(Co$_{1}$3/Nb$_{2}$3/)O$_3$[BCN] contents and the possibility of application as a microwave dielectric resonator were investigated. The specimens were prepared by he conventional mixed oxide method using there sintering temperature of 1575$^{\circ}C$. It was found that Ba(Mg$_{1}$3/Ta$_{2}$3/)O$_3$[BMT] and BCN formed a solid solution with complex perovskite structure. As the mole fraction of BCN increased, dielectric constant increased while temperature coefficient of resonant frequency decreased. The highest value of quality factor, Qxf$_{0}$=138,205GHz, obtained in the sample of 0.9BMT-0.1BCN ceramics. In the range of x$\geq$0.4, the dielectric constant was about 30. The 0.55BMT-0.45BCN ceramics showed excellent microwave dielectric properties with $\varepsilon$$_{r}$=30.84, Qxf$_{0}$=75,325GHz and $\tau$$_{f}$=2.9015ppm/$^{\circ}C$.EX>.EX>.

• 광물과 암석
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• 제36권3호
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• pp.185-197
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• 2023

구봉 금-은 광상은 선캠브리아기의 변성퇴적암류내에 발달된 열극대를 충진한 8개조의 석영맥으로 구성된 조산형과 intrusion-related형이 혼합된 광상으로 과거 한국에서 가장 큰 금-은 광상들 중의 하나였다. 대한광업진흥공사는 이 광상의 남부에서 시추(90-12)를 통한 심도 -728 ML에서 27.9 g/t Au 품위를 갖는 0.9 m 폭을 갖는 석영맥(6호맥)을 착맥하였으며 2004년 재차 6호맥의 재개발 가능성 검토를 위해 시추(04-1)를 수행하였다. 2004년 시추 현장에서 모암, 모암변질 및 석영맥 시료들(04-1)을 채취하여 함 티타늄 광물들(티탄철석, 금홍석)의 산상과 화학조성을 연구하였다. 심도 -275 ML의 광화대에서 관찰되는 금홍석은 모암변질대에서 칼리장석, 흑운모, 석영, 방해석, 녹니석 및 황철석과 함께 산출된다. 심도 -779 ML의 광맥(6호맥)에서 관찰되는 티탄철석과 금홍석은 모암변질대와 석영맥에서 백색운모, 녹니석, 인회석, 저어콘, 석영, 방해석, 자류철석 및 황철석과 함께 산출된다. 이들 광물조합을 토대로, 금홍석은 열수 용액에 의한 모암내 Ti을 풍부하게 함유한 흑운모의 열수변질작용(녹니석화작용) 시 형성된 것으로 생각된다. 티탄철석은 최대 0.09 wt.% (HfO₂), 0.39 wt.% (V₂O₃), 0.54 wt.% (BaO) 함량이 함유되어 있다. 심도 -275 ML과 -779 ML에서 산출되는 금홍석의 화학조성을 비교하면, 심도 -779 ML의 광맥(6호맥)의 금홍석에서 WO₃, FeO 및 BaO 원소들의 함량이 높다. 이들 미량원소들은 심도 -275 ML의 금홍석 Ba²⁺ + Al³⁺ + Hf⁴⁺ + (Nb⁵+, Ta⁵⁺) ↔ 3Ti⁴⁺ + Fe²⁺, 2V⁴⁺ + (W⁵⁺, Ta⁵⁺, Nb⁵⁺) ↔ 2Ti⁴⁺ + Al³⁺ + (Fe²⁺, Ba²⁺), Al³⁺ + V⁴⁺ + (Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + 2Fe²⁺, 심도 -779 ML의 금홍석 2(Fe²⁺, Ba²⁺) + Al³⁺ + (W⁵⁺, Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + (V⁴⁺, Hf⁴⁺), Fe²⁺ + Al³⁺ + Hf⁴⁺ + (W⁵⁺, Nb⁵⁺, Ta⁵⁺) ↔ 2Ti⁴⁺ + V⁴⁺ + Ba²⁺로써 치환관계가 있었다. 이들 자료와 기 연구된 조산형 금 광상에서 산출되는 함 티타늄 광물들의 화학조성과 비교 검토 본 결과, 구봉 광상의 금홍석들은 다른 조산형 금 광상(운산 광상, Kori Kollo 광상, Big Bell 광상, Meguma 함 금 석영맥)들에서 산출되는 금홍석들보다 상대적으로 산화 환경에서 형성되었음을 알 수 있다.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1719-1723
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• 2014

In this study, the microwave dielectric properties of nano spheroidization glass powders added $Ba(Zn_{1/3}Ta_{2/3})O_3$ ceramics prepared by solid state reaction have been investigated. Adding $(Ba_{0.4}Ca_{0.6})SiO_3$ nano spheroidization glass powders could effectively promote the densification even in the case of decreasing the sintering temperature. When the glass frit is 0.3 wt% and sintering is carried out at a temperature of $1500^{\circ}C$ for 6 hr, a temperature stable microwave dielectric ceramic could be obtained, which has a dielectric constant (${\varepsilon}_r$) of 30.2, a quality factor ($Q{\times}f_0$) of 124,000 GHz and a temperature coefficient of resonance frequency (${\tau}_f$) of $2ppm/^{\circ}C$.

• E2M - 전기 전자와 첨단 소재
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• 제9권4호
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• pp.336-343
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• 1996

We have studied the preparation and the properties of $Ba_{1-x}$Sr$_{x}$TiO$_{3}$(BST) thin films by using the sol-gel method. Through the comparison of the effects of various solvents and additives in making solutions, we establish the production method of the stable solution which generates the high quality of BST film. We also set up the heat-treatment conditions for depositing the BST thin film through the TGA and XRD analyses. Through the comparison of the surface conditions of BST films deposited on Pt/Ta/SiO$_{2}$/Si and Pt/Ti/SiO$_{2}$/Si substrates, we find that Ta is more efficient diffusion barrier of Si than Ti so that Ta layer prevents the formation of hillocks. We fabricate the planar type capacitor and measure the dielectric properties of the BST thin film deposited on the Pt/Ta/SiO$_{2}$/Si substrate. Dielectric constant and dielectric loss tangent at 1V, 10kHz, and leakage current density at 3V of the BST thin film are 339, 0.052 and 13.3.mu.A/cm$^{2}$, respectively.ely.

• 한국세라믹학회지
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• 제56권4호
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• pp.399-402
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• 2019

The phase evolution, microstructure, and microwave dielectric properties of (Ba_1-xNa_x)(Mg_0.5-2xY_2xW_0.5-xTa_x)O₃ (0 ≤ x ≤ 0.05) ceramics were investigated. All compositions exhibited a 1:1 ordered perovskite structure. As the value of x increased, the dielectric constant (ε_r) exhibited a tendency to increase slightly. The quality factor reached the maximum value at x = 0.01. The temperature coefficient of resonant frequency (τ_f) increased from -19.32 ppm/℃ to -5.64 ppm/℃ in the positive direction as x increased. The dielectric constant (ε_r), quality factor (Q × f₀), and temperature coefficient of resonant frequency (τ_f) of the composition x = 0.05, i.e., (Ba_0.95Na_0.05)(Mg_0.4Y_0.1W_0.45Ta_0.05)O₃ were 19.9, 128,553 GHz, and -5.6 ppm/℃, respectively.

• 한국재료학회지
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• 제28권9호
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• pp.489-494
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• 2018

Lead free $(1-x)(0.675BiFeO_3-0.325BaTiO_3)-xLiTaO_3$ (BFBTLT, x = 0, 0.01, 0.02, and 0.03, with 0.6 mol% $MnO_2$ and 0.4 mol% CuO) were prepared by a solid state reaction method, followed by air quenching and their crystalline phase, morphology, dielectric, ferroelectric and piezoelectric properties were explored. An X-ray diffraction study indicates that lithium (Li) and tantalum (Ta) were fully incorporated in the BFBT materials with the absence of any secondary phases. Dense ceramic samples (> 92 %) with a wide range of grain sizes from $3.70{\mu}m$ to $1.82{\mu}m$ were obtained in the selected compositions ($0{\leq}x{\leq}0.03$) of BFBTLT system. The maximum temperatures ($T_{max}$) were mostly higher than $420^{\circ}C$ in the studied composition range. The maximum values of maximum polarization ($P_{max}{\approx}31.01{\mu}C/cm^2$), remnant polarization ($P_{rem}{\approx}22.82{\mu}C/cm^2$) and static piezoelectric constant ($d_{33}{\approx}145pC/N$) were obtained at BFBT-0.01LT composition with 0.6 mol% $MnO_2$ and 0.4 mol% CuO. This study demonstrates that the high $T_{max}$ and $d_{33}$ for BFBTLT ceramics are favorable for industrial applications.