• 한국재료학회:학술대회논문집
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• 한국재료학회 2005년도 춘계학술발표대회 및 제8회 신소재 심포지엄 논문개요집
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• pp.35-35
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• 2005

• 한국세라믹학회지
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• 제16권1호
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• pp.26-30
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• 1979

The microstructures and memory core characteristics of substituted lithium ferrites with addition of $Bi_2O_3$, $V_2O_5$, $Nb_2O_3$, and $P_2O_5$ were investigated. The effects of composite flux on the sintering of the substituted lithium ferrites were also studied. The results show that the addition of $Bi_2O_3$, $V_2O_5$, and $Nb_2O_5$ enhances sintering whereas $Sb_2O_3$ and $P_2O_5$ inhibits it, and that the addition of $Nb_2O_5$ results in uniform grain size while the addition of $Bi_2O_3$ or $V_2O_5$ results in non-uniformity in grain size. When $P_2O_5$ was added with $V_2O_5$ or $Bi_2O_3$, however, it results in uniform grain size and improved memory core properties.

• 공업화학
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• 제33권1호
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• pp.64-70
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• 2022

본 연구에서는 NH₃-SCR에서 VWTi촉매의 저온 탈질효율 증진을 위해 Sb을 첨가하여 실험을 수행하였으며 Sb 첨가에 있어 다양한 소성온도(400~700 ℃)에서 제조하였다. NH₃-SCR 실험 결과 Sb 소성온도 500~600 ℃에 해당하는 VWSbTi(500)와 VWSbTi(600) 촉매가 300 ℃ 이하의 저온에서 가장 우수한 탈질성능을 나타냈으며, 소성온도에 따른 물리화학적 특성을 확인하고자 BET, XRD, Raman, XPS, H₂-TPR, NH₃-TPD 분석을 수행하였다. VWSbTi(500)와 VWSbTi(600)의 경우 W=O종의 생성에 따라 암모니아 산점이 증가하였으며 텅스텐의 전자밀도 증가에 따른 우수한 redox 특성으로 저온에서 우수한 활성을 나타내었다. 또한 VWSbTi(700)의 경우 V₂O₅ 결정구조가 형성되어 활성이 저하됨에 따라 Sb 첨가과정에 있어 최적의 소성온도를 확인하였다.

• 한국전기전자재료학회논문지
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• 제23권8호
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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.

• 한국전기전자재료학회논문지
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• 제29권4호
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• pp.205-209
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• 2016

In this paper, piezoelectric ceramics with the composition of $(Na_{0.525}K_{0.4425}Li_{0.0375})(Nb_{0.8975}Sb_{0.065}Ta_{0.0375})O_3+0.3wt%\;CoO+x\;CuO$ ($0.005{\leq}x{\leq}0.025$) (abbreviated to NKL-NST) were fabricated for ultrasonic sensor application. The effects of CuO addition and sintering on the microstructure and the piezoelectric properties of the NKL-NST ceramics were systematically studied. Excellent piezoelectric properties such as electromchanical coupling $factor(k_p)=0.415$, piezoelectric constant $(d_{33})=166pC/N$ and piezoelectric figure of merit $d_{{33}*}g_{33}=5.47pm^2/N$ were obtained from the 2.5 mol% CuO doped NKL-NST+0.3 wt%CoO ceramics sintered at $1,000^{\circ}C$ for 3 h.

• 전기학회논문지
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• 제59권11호
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• pp.2021-2025
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• 2010

Electrical and structural properties were investigated on the effects of ZnO and the lead-free NKN-LST ceramics with the addition of ZnO were fabricated by a conventional mixed oxide method. A gradual change in the crystal and microstructure was observed with the increase of ZnO addition. For the NKN-LST-ZnO ceramics sintered at $1050^{\circ}C$, bulk density increased with the addition of ZnO and showed maximum value at addition 2.0mol% of ZnO. Curie temperature of the NKN-LST-ZnO ceramics slightly decreased with adding ZnO. The dielectric constant, piezoelectric constant ($d_{33}$) and electromechanical coupling factor ($k_p$) increased at the small amount of ZnO addition, which might be due to the increase in density. The high piezoelectric properties = 153 pC/N, electromechanical coupling factor = 0.484 and dielectric constant = 2883 were obtained for the NKN-LST+0.5ZnO ceramics sintered at $1050^{\circ}C$ for 2h.

• 한국전기전자재료학회논문지
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• 제23권11호
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• pp.854-858
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• 2010

In this study, we have investigated the effects of Cr dopant on the sintering and electrical properties of ZnO-$Sb_2O_3$ (ZS) ceramics for varistor application. Spinel phases including $\alpha-$ and $\beta$-type was formed at ZS system and $\alpha$-spinel was stabilized by Cr doping in ZS system. Densification of ZS and ZSCr system was retarded to $1000^{\circ}C$ by the formation of spinel at $800^{\circ}C$. The morphology and its distribution of spinel phases in ZS system was homogeneous but disturbed by Cr doping. In ZSCr the densification of ZnO compared with ZS system was more retarded by low concentration of Zn interstitial defects induced by Cr doping in addition to the effect of spinel phase formation. The defects in each system were identified as attractive coulombic center (ZS: 0.13 eV, ZSCr: 0.12 eV) and singly charged oxygen vacancy $V_0^{\cdot}$ (ZSCr: 0.33 eV). In all ZS and ZSCr system have week varistor behavior by the formation of double Schottky barrier at grain boundary but its stability of barrier was very sensitive to sintering temperature.

• JSTS:Journal of Semiconductor Technology and Science
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• 제11권3호
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• pp.146-152
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• 2011

Thermal stability of $Ge_2Sb_2Te_5$ (GST) and $SiO_2$ doped GST (SGST) films for phase change random access memory applications was investigated by observing the change of surface roughness, layer density and composition of both films after isothermal annealing. After both GST and SGST films were annealed at $325^{\circ}C$ for 20 min, root mean square (RMS) surface roughness of GST was increased from 1.9 to 35.9 nm but that of SGST was almost unchanged. Layer density of GST also steeply decreased from 72.48 to 68.98 $g/cm^2$ and composition was largely varied from Ge : Sb : Te = 22.3 : 22.1 : 55.6 to 24.2 : 22.7 : 53.1, while those of SGST were almost unchanged. It was confirmed that the addition of a small amount of $SiO_2$ into GST film restricted the deterioration of physical and chemical properties of GST film, resulting in the better thermal stability after isothermal annealing.

• Transactions on Electrical and Electronic Materials
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• 제12권2호
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• pp.72-75
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• 2011

In this study, $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3+0.9$ mol% $K_{5.4}Cu_{1.3}Ta_{10}O_{29}+x$ mol% $K_4CuNb_8O_{23}$ (x = 0, 0.2, 0.6, 0.8) ceramics were prepared by a conventional mixed oxide method. Their microstructure and electric properties were investigated. The secondary phase was made by virtue of $K_4CuNb_8O_{23}$ (KCN) addition in the $(K_{0.5}Na_{0.5})(Nb_{0.97}Sb_{0.03})O_3$ system ceramics. However, the sinterability of the ceramics increased with increasing $K_4CuNb_8O_{23}$ content. At the 0.6 mol% $K_4CuNb_8O_{23}$ added composition ceramics sintered at $1,060^{\circ}C$, kp and $d_{33}$ showed the optimum values of 0.39 and 145 pC/N, respectively, suitable for piezoelectric actuator application.

• 공업화학
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• 제32권1호
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• pp.35-41
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• 2021

NH3-SCR에서 상용촉매로 사용되고 있는 VWTi (VOx/WO3-TiO2)는 300~400 ℃에서 우수한 탈질성능을 나타내지만 300℃ 이하 저온에서는 효율이 저하되는 문제가 있다. 저온 탈질효율을 높이기 위하여 promoter를 첨가한 촉매 연구는 꾸준히 진행되고 있으나 촉매의 저온 탈질효율 증진원인과 촉매특성에 관한 연구는 미비한 실정이다. 본 연구에서는 VWTi에 Sb(antimony)를 첨가함으로써 300 ℃ 이하의 NH3-SCR 반응에서 탈질 성능이 10% 이상 증진되는 것을 확인하였고, 이 때 외부확산/내부확산에 의한 영향을 배제하고자 공간속도와 촉매입자 크기를 제어하였다. 또한 Sb의 첨가 유·무에 따른 촉매특성을 BET, TEM/EDS, O2-TPD, H2-TPR, DRIFTs 분석을 수행하여 고찰하였다. Sb의 첨가는 촉매의 표면 흡착 산소 종을 증가시켰으며, 이에 따라 저온에서 촉매의 산화·환원(redox) 특성이 증진되어 우수한 탈질성능을 나타내는 것으로 판단되었다.