• Transactions on Electrical and Electronic Materials
• /
• v.15 no.5
• /
• pp.284-289
• /
• 2014

The effects of additives (Nb, Bi and Cr) on the microstructure, varistor properties, and aging behavior of V/Mn/Co/ La/Dy co-doped zinc oxide ceramics were systematically investigated. An analysis of the microstructure showed that all of the ceramics that were modified with various additives were composed of zinc oxide grain as the main phase, and secondary phases such as $Zn_3(VO_4)_2$, $ZnV_2O_4$, and $DyVO_4$. The $Bi_2O_3$-modified samples exhibited the lowest density, the $Nb_2O_5$-modified sample exhibited the largest average grain size, and the $Cr_2O_3$-modified samples exhibited the highest breakdown field. All additives improved the non-ohmic coefficient (${\alpha}$) by either a small or a large margin, and in particular an $Nb_2O_5$ additive noticeably increased the non-ohmic coefficient to be as large as 36. The $Bi_2O_3$-modified samples exhibited the highest stability with variation rates for the breakdown field and for the non-ohmic coefficient (${\alpha}$) of -1.2% and -26.3%, respectively, after application of a DC accelerated aging stress of 0.85 EB/$85^{\circ}C$/24 h.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05b
• /
• pp.47-53
• /
• 2003

자발착화연소법과 분무열분해법을 동시에 적용한 초음파분무연소법을 이용하여 40~50nm 크기를 갖는 결정성 ZnO 분말을 합성하였다. 또한 바리스터로의 응용을 위해 Bi, Sb, Co, Mn을 초기출발원료인 Zn-nitrate에 첨가하여 복합조성의 ZnO계 바리스터 분말을 합성하였다. 합성된 바리스터의 분말을 성형 및 소결하여 전기적 특성을 관찰한 결과 Co를 첨가한 분말보다 Mn을 첨가한 분말에서 우수한 전기적 특성을 나타내었다.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1999.11a
• /
• pp.217-220
• /
• 1999

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-0 ceramics. The doping elements can be classified into groups depending on their supeconducting characteristics in the Bi -Sr-Ca-Cu -O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.344-345
• /
• 2005

The characteristics of varistors based on M.Matstuokas with one another ZnO powder (50nm, 100nm, 300nm) have been investigated. The optimum calcination and sintering temperature was also selected for each samples. Varieties of sintering conditions were found according to powder size. As the result of analysises on each operating voltages. We obtained the most high voltage in a sample with 50nm ZnO powder.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1990.10a
• /
• pp.71-77
• /
• 1990

This paper is studied on the sintering characteristics of Ni-Zn ferrites. The specimen ferrites was composed of 20 mol% NiO, 30mol% ZnO, 50 mol% Fe$_2$O$_3$, and 0.0025 mol%, 0.005 mol%, 0.01 mol% Nb$_2$O$\_$5/, Bi$_2$O$_3$, V$_2$O$\_$5/, wee used as minor additives. Sintering was carried out at 1100$^{\circ}C$. As results from the experiments, the high value of initial permeability of 6X10$^2$∼9X10$^2$ can be achieved at 500KHz∼1000KHz. The value of loss factor 1X10￣$^2$∼2X10$^2$ can be achieved at 500KHz∼1000KHz. The lowest 1/(${\mu}$XQ) value was obtained in the specimen with the addition of 0.005mol% fracyion for V$_2$O$\_$5/.

• Korean Journal of Materials Research
• /
• v.32 no.10
• /
• pp.435-441
• /
• 2022

We report the synthesis and gas sensing properties of bare and ZnO decorated TeO₂ nanowires (NWs). A catalyst assisted-vapor-liquid-solid (VLS) growth method was used to synthesize TeO₂ NWs and ZnO decoration was performed using an Au-catalyst assisted-VLS growth method followed by a subsequent heat treatment. Structural and morphological analyses using X-ray diffraction (XRD) and scanning/transmission electron microscopies, respectively, demonstrated the formation of bare and ZnO decorated TeO₂ NWs with desired phase and morphology. NO₂ gas sensing studies were performed at different temperatures ranging from 50 to 400 ℃ towards 50 ppm NO₂ gas. The results obtained showed that both sensors had their best optimal sensing temperature at 350 ℃, while ZnO decorated TeO₂ NWs sensor showed much better sensitivity towards NO₂ relative to a bare TeO₂ NWs gas sensor. The reason for the enhanced sensing performance of the ZnO decorated TeO₂ NWs sensor was attributed to the formation of ZnO (n)/ TeO₂ (p) heterojunctions and the high intrinsic gas sensing properties of ZnO.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07a
• /
• pp.569-572
• /
• 2003

전력선 통신용 LC 공진필터에 사용되는 Ni-Zn 페라이트를 제조하기 위해 Ni0.8Zn0.2Fe2O4를 기본조성으로 선택하고 x (Co mol 비)를 변화시켜 전자기적 특성을 조사하였다. $Bi_2O_3$ CaO가 첨가됨으로써 균일한 입자성장과 입계에 고저항층이 형성되어 주파수 손실이 감소하였으며, $Ni_{0.8-x}Zn_{0.2}Co_xFe_2O_{\delta}$의 기본조성에 Co의 함량을 증가시키면 x = 0.05에서 투자율 75, 공진주파수 20 MHz의 특성을 나타내고 결정 입자 크기와 같은 구조적 특성에는 영향을 거의 미치지 않지만 자기이방성 변화에 따라 전자기적 특성에는 영향을 미친다. 또한, $Ni_{0.75}Zn_{0.2}Co_{0.05}Fe_2O_{4.017}$ 조성의 페라이트 코어의 발열량은 큐리온도 이하에서 일어난다.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.178.1-178.1
• /
• 2015

In and Ga doped ZnO (IGZO) thin films were prepared by radio frequency magnetron sputtering without intentional substrate heating on glass substrate and TiO2-deposited glass substrates to consider the effect of a thin TiO2 buffer layer on the optical and electrical properties of the films. The thicknesses of the TiO2 buffer layer and IGZO films were kept constant at 5 and 100 nm, respectively. Since the IGZO/TiO2 bi-layered films show the higher FOM value than that of the IGZO single layer films, it is supposed that the IGZO/TiO2 bi-layered films will likely perform better in TCO applications than IGZO single layer films.

• Electrical & Electronic Materials
• /
• v.9 no.1
• /
• pp.1-8
• /
• 1996

We investigated the effects of doping elements on the Bi-Sr-Ca-Cu-O ceramics. The doping elements can be classified into four groups depending on their supeconducting characteristics in the Bi-Sr-Ca-Cu-O structure. The first group of doping elements(Co, Fe, Ni and Zn) substitute into the copper site and can reduce the critical temperatures of the 2223 and 2212 phases. The second group of doping elements(Y and La) substitute into the Ca site and cause the disappearance of the 2223 phase and increase the critical temperatures in the 2212 phase. The third group of doping elements(P and K) have a tendency to decompose the superconducting phase and reduce the optimal sintering temperature. The fourth group of doping elements(B, Si, Sn and Ba) almost unaffected the superconductivity of the 2223 and 2212 phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.05c
• /
• pp.282-286
• /
• 2003

We investigated the effects of calcination temperature and sintering additives on the sintering behaviors and microwave dielectric properties of $(Zn_{0.8}Mg_{0.2})TiO_3$. Highly densified samples were obtained at the sintering temperatures below $1000^{\circ}C$ with additions of 0.45 wt.% $Bi_2O_3$ and 0.55 wt.% $V_2O_5$. From the examination of the existing phases and microstructures before and after sintering of $(Zn_{0.8}Mg_{0.2})TiO_3$ system calcined at the various temperatures ranging from $800^{\circ}C$ to $1000^{\circ}C$, it was found that high $Q{\times}f_o$ values were obtained when unreacted or second phases in calcined body were reduced. When calcined at $1000^{\circ}C$ and sintered at $900^{\circ}C$, it consists of hexagonal as a main phase with uniform microstructure and exhibits $Q{\times}f_o$ value of 42,000 GHz and dielectric constant of 22.