• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1232-1233
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• 2006

To co-fire with commercial LTCC (Low Temperature Co-fired Ceramic) materials at $850^{\circ}C{\sim}880^{\circ}C$, different contents of $B_2O_3$ were added to the $Bi_2O_3-ZnO-Nb_2O_5$ (BZN) ceramics. According to the test results, the cubic phase of BZN was transformed into orthorhombic in all the test materials. $BiNbO_4$ phase was formed in test materials with $2{\sim}5wt%$ of $B_2O_3$ addition. The phase transformation of cubic BZN was controlled during the synthesis process with excess ZnO content. The Cubic and orthorhombic phases of BZN could coexist and be sintered densely at $850^{\circ}C/2hr$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.4
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• pp.210-214
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• 2016

We investigated the sintering behavior and piezoelectric properties of lead-free $(K_{0.5}Na_{0.5})NbO_3$ ceramics co-doped with excess 0.01 mol ZnO and x mol $MnO_2$, where x was varied from 0 to 0.03. Excess $MnO_2$ addition was found to retard the grain growth and densification during sintering. However, 0.005 mol $MnO_2$ addition improved the piezoelectric properties of 0.01 mol ZnO added $(K_{0.5}Na_{0.5})NbO_3$ ceramics. The planar mode piezoelectric coupling coefficient, electromechanical quality factor, and piezoelectric constant $d_{33}$ of 0.01 mol ZnO and 0.005 mol $MnO_2$ added specimen were 0.40, 304, and 214 pC/N, respectively.

• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.429-436
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• 2012

Mg and Mg-based alloys are regarded as strong candidate hydrogen storage materials since their hydrogen capacity exceeds that of known metal hydrides. One of the approaches to improve kinetic is addition of metal oxide. In this paper, we tried to improve the hydrogenation properties of Mg-based hydrogen storage composites. The effect of transition metal oxides, such as $Nb_2O_5$ on the kinetics of the Magnesium hydrogen absorption kinetics was investigated. $MgH_x$-5wt.% $Nb_2O_5$ composites have been synthesized by hydrogen induced mechanical alloying. The powder fabricated was characterized by X-ray diffraction (XRD), Field Emission-Scanning Electron Microscopy (Fe-SEM), Energy Dispersive X-ray (EDX), BET and simultaneous Thermo Gravimetric Analysis / Differential Scanning Calorimetry (TG/DSC) analysis. The Absorption / desorption kinetics of $MgH_x$-5wt.% $Nb_2O_5$ (type I and II) are determined at 423, 473, 523, 573 and 623 K.

• Korean Journal of Materials Research
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• v.29 no.3
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• pp.150-154
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• 2019

This study investigates the effect of MnO2 and CuO as acceptor additives on the microstructure and piezoelectric properties of $0.96(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}Nb_{0.93}Sb_{0.07}O_3-0.04BaZrO_3$, which has a rhombohedral-tetragonal phase boundary composition. $MnO_2$ and CuO-added $0.96(K_{0.5}Na_{0.5})_{0.95}Li_{0.05}Nb_{0.93}Sb_{0.07}O_3-0.04BaZrO_3$ ceramics sintered at a relatively low temperature of $1020^{\circ}C$ show a pure perovskite phase with no secondary phase. As the addition of $MnO_2$ and CuO increases, the sintered density and grain size of the resulting ceramics increases. Due to the difference in the amount of oxygen vacancies produced by B-site substitution, Cu ion doping is more effective for uniform grain growth than Mn ion doping. The formation of oxygen vacancies due to B-site substitution of Cu or Mn ions results in a hardening effect via ferroelectric domain pinning, leading to a reduction in the piezoelectric charge coefficient and improvement of the mechanical quality factor. For the same amount of additive, the addition of CuO is more advantageous for obtaining a high mechanical quality factor than the addition of $MnO_2$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.6
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• pp.517-523
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• 2008

The microwave dielectric properties of $LiNb_3O_8-TiO_2$ based ceramics with low firing agents, CuO, $Bi_2O_3$, $B_2O_3$, $SiO_2$, $TiO_2$, were investigated to improve the sintering condition for the LTCC system. According to the X-ray diffraction and SEM, the ceramics of $LiNb_3O_8-TiO_2$ with low firing agents showed no significant second phases within a range of experiments, and fine microstructures. By adding the low firing agents, the sintering temperature decreased from $1200^{\circ}C$ to $925^{\circ}C$. Based on the results of electrical measurements, the $LiNb_3O_8-TiO_2$ ceramics showed a promising microwave dielectric properties for LTCC applications, those are ${\varepsilon}_r$ (dielectric constant) = 44, Q f (quality factor) = 18000, and ${\tau}_f$ (the temperature coefficient of resonant frequency) = $-1.5\;ppm/^{\circ}C$.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1025-1028
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• 2006

Dense $0.95(Na_{0.5}K_{0.5})NbO_3-0.05LiTaO_3$ (NKN-5LT) ceramics were developed by conventional sintering process. Sintering temperature was lowered by adding $Na_2CO_3$ as a sintering aid. The electrical properties of NKN-5LT ceramics were investigated as a function of $Na_2CO_3$ concentration. When the sample sintered at $1000^{\circ}C$ for 4 h with the addition of 1 mol% $Na_2CO_3$, electro-mechanical coupling factor $(k_p)$ and piezoelectric coefficient $(d_{33})$ of NKN-5LT ceramics were found to reach the highest values of 0.43 and 190 pC/N, respectively.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2004.04a
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• pp.42-43
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• 2004

• Journal of the Korean Ceramic Society
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• v.37 no.10
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• pp.968-974
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• 2000

Nb$_2$O$_{5}$와 MnO 첨가에 따른 Pb$_{0.6}$Sr$_{0.4}$TiO$_3$반도체 세라믹의 미세구조와 전기적 특성은 유전특성, I(current)-V(voltage) 측정, 그리고 복소 임피던스 측정 등을 이용하여 고찰하였다. Nb 도핑량이 0.4 mol% 이하인 경우 Nb 도핑량에 따라 전도성과 입성장은 증가되었으나 그 이상의 도핑량에서는 Sr이나 Pb 공공의 생성으로 인하여 전도성이 감소되고 입성장도 억제되는 것을 관찰할 수 있었다. 0.4 mol% Nb-doped Pb$_{0.6}$Sr$_{0.4}$TiO$_3$에 0.01 mol% MnO를 첨가한 경우 비저항비($ ho$$_{max}$/$\rho$/min/)가 $10^2$에서 $10^4$으로 크게 향상되었다. 그리고 전이 온도 주변에서 여러 개의 변곡점을 지니는 비옴성 거동이 발견되었다. 이와 같은 현상은 입계에 존재하는 Mn 이온이 부분적으로 편석되어 표면 전하의 보상 효과에 영향을 미치는 것이라고 사료된다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.11 no.5
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• pp.378-383
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• 1998

Microstructure and additive effect of Lead Zirconate-Titanate(PZT) ceramics prepared by molten salt synthesis method with additives $Nb_2O_5, Fe_2O_3$ and MnO were investigated.The grain PZT ceramics ws decreased with the increase $Nb^{5+} or Fe^{3+}$ while increased with the increase $Mn^{2+}$ addition. The relative resistivity of PZT ceramics was increased with the increase $Mn^{5+}$ addition, while decreased with the increase $Mn^{2+}$ addition. And the dielectric and the piezoelectric constant of PZT ceramics showed 2,100 and 342pC/N at $Mn^{5+}$ addition of 0.75 mol%, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.8
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• pp.617-621
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• 2010

($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ ceramics doped with iron oxide ($Fe_2O_3$) were prepared by a conventional mixed oxide method. And then, their piezoelectric and dielectric properties were investigated as a function of $Fe_2O_3$ addition. X-ray diffraction studies reveal that $Fe^{3+}$ diffuses into the NKN lattices to form a solid solution with a pure perovskite structure at room temperature. At the sintering temperature of $1,060^{\circ}C$, when 0.2 mol% $Fe_2O_3$ was doped, the piezoelectric constant ($d_{33}$), electromechanical coupling factor (Kp), and mechanical quality factor ($Q_m$) showed the excellent values of 131.67 pC/N, 0.436, and 696.36, respectively. Results show that $Fe_2O_3$ deped ($K_{0.5}Na_{0.5}$)($Nb_{0.96}Sb_{0.04}$)$O_3$+1.2 mol% $K_4CuNb_8O_{23}$ lead-free piezoelectric ceramics are a promising lead free material for piezoelectric transformer applications.