• 한국전기전자재료학회논문지
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• 제17권9호
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• pp.924-929
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• 2004

The microstructure, electrical and dielectric characteristics of $ZnO-{Pr}_6{O}_11-{CoO}-{Dy}_2{O}_3$-based varistors were investigated without and with various metal oxide additives(NiO, MgO, Cr$_2$O$_3$). The average grain size decreased in the range of 18.4 $\backsim$ 11.5 $\mu$m, in order of NiO\longrightarrowMgO\longrightarrow{Cr}_2{O}_3$ and the density decreased in the range of 5.62 \backsim 5.33 $g/{cm}^3$ in order of NiO\longrightarrowCr$_2$O$_3$\longrightarrowMgO. While, the nonlinear exponent increased In the range of 19.8$\backsim$67.4 in order of NiO\longrightarrowMgO\longrightarrow${Cr}_2{O}_3$ and the leakage current decreased in the range of 25.6 $\backsim$ 1.2 $\mu$A in order of NiO\longrightarrow${Cr}_2{O}_3$\longrightarrowMgO. Among all varistors, the Cr$_2$O$_3$-added varistor exhibited the highest nonlinearity, with a nonlinear exponent of 67.4 and a leakage current of 1.2 $\mu$A. Furthermore, this varistor exhibited the lowest dielectric dissipation factor of 0.0407.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.373-376
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• 2001

When varistors for circuit protection is used at high voltage, it's operation properties were unstable because of leakage current and nonlinear coefficient with grain size. For the purpose of improving of ZnO varistor properties, high voltage ZnO varistor was fabricated with Y$_2$O$_3$addition. Electrical properties were investigated according to sintering conditions and mixing conditions. ZnO varistors was shown ohmic Properties when it's applied voltage was below critical voltage. It was shown non-ohmic properties over critical voltage, because current was increased with decreasing resistance.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1995년도 추계학술대회 논문집
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• pp.29-33
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• 1995

The ($Ba_{0.85}Ca_{0.15}$)$TiO_3$-Zndielectrics was made by ZnO mol ratio from 0.1 to 0.4. The characteristics of structural was analyzed by SEM and XRD and the insulating properties was examined by dielectric constant and resistivity. The grain size were 1.3[$\mu\textrm{m}$] and those shape ware a rectangular. The relativity density were over 90[%] in all specimen. It was found that the best insulating characteristics were obtained for 0.3 mol ratio.

• 한국자기학회지
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• 제9권6호
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• pp.278-284
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• 1999

Mn-Zn ferrites에 TiO2가 첨가될 때 전력손실, 밀도, 초기투자율, 저항, 그리고 미세구조의 변화를 관찰하였다. 첨가량이 증가함에 따라 밀도는 증가했지만, 초기투자율은 감소하였다. TiO2의 첨가에 따라 electron hopping을 일으키는 활성화에너지와 전기저항이 증가하였다. 115$0^{\circ}C$에서 소결한 TiO2를 1.5 wt% 첨가한 시편은 1 MHz, 25 mT, 8$0^{\circ}C$에서 83 mW/㎤의 전력손실을 나타내었다. 그러나 120$0^{\circ}C$에서 소결할 때는 과대입성장이 발생하여 같은 측정 조건에서 1168 mW/㎤의 전략손실을 얻었다.

• 한국세라믹학회지
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• 제16권3호
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• pp.142-154
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• 1979

The effects of microstructures and some additives $(CoO and Al_2O_3$) on the magnetic properties such as initial permeability, $\mu$-T curve, coercive force, and magnetic induction of MnZn ferrites have been studied. The powder was prepared by Hot Petroleum Drying Method. The basic composition of MnZn ferrites was 25.5mole % MnO, 22.0 mole% ZnO, 52.5 mole% $Fe_2O_3$. CoO in a concentration range from 0.05 to 0.5 mole% and $Al_2O_3$ from 2.5 to 7.5 mole% were added. Sintered density increased up to 97.5% of theoretical density. Permeability increased as average grain size increased, and that coercive force decreased as average grian size increased. Magnetic induction increased as sintered density increased. The variation of initial permeability with temperature in a temperature range from 0$^{\circ}$ to $60^{\circ}C$ was lowered (a flatter $\mu-T$ curve) as sintering temperature decreased. The compensation temperature To ofmagnetocrystalline anisotropy constant K1 and initial permeability varied with the species and amount of additives. When 0.05 mole% CoO was added to the basic composition, initial permeability at $15^{\circ}C$ increased from 5200 to 5900. The variation ofinitial permeability with temperature in a temperature range from 0^{\circ}to $60^{\circ}C$ was smaller (a flatter $\mu$-T curve) than that of the basic composition of Mn Zn ferrites. When 2.5 mole% $Al_2O_3$ was added, initial permeability at $15^{\circ}C$ decreased from 5200 to 3000. But the variation of initial permeability with temperature in a temperature range from 0$^{\circ}$to $60^{\circ}C$ was smaller (a flat ter $\mu-T$ curve) than when 0.05 mole% CoO was added. Experimental results showed that the conditions necessary for the occurrence of a very high permeability and a flat $\mu$-T curve were controversial even in a temperature range from $0^{\circ}$to $60^{\circ}C$.

• 한국전기전자재료학회논문지
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• 제22권11호
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• pp.941-948
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• 2009

The present study aims at the examination of the effects of 1 mol% NiO addition on the reaction, microstructure development, resultant electrical properties, and especially the bulk trap and interface state levels of $ZnO-Bi_2O_3-Sb_2O_3$ (Sb/Bi=0.5, 1.0, and 2.0) systems (ZBS). The samples were prepared by conventional ceramic process, and characterized by density, XRD, SEM, I-V, impedance and modulus spectroscopy (IS & MS) measurement. The sintering and electrical properties of Ni-doped ZBS (ZBSN) systems were controlled by Sb/Bi ratio. Pyrochlore ($Zn_2Bi_3Sb_3O_{14}$) was decomposed more than $100^{\circ}C$ lowered in ZBS (Sb/Bi=1.0) by Ni doping. The reproduction of pyrochlore was suppressed by the addition of Ni in ZBS. Between two polymorphs of $Zn_7Sb_2O_{12}$ spinel ($\alpha$ and $\beta$), microstructure of ZBSN (Sb/Bi=0.5) composed of a-spinel was more homogeneous than $Sb/Bi{\geq}1.0$ composed of $\beta$-spinel phase. In ZBSN, the varistor characteristics were not improved drastically (non-linear coefficient $\alpha\;=\;6{\sim}11$) and independent on microstructure according to Sb/Bi ratio. Doping of Ni to ZBS seemed to form ${V_0}^{\cdot}$ (0.33 eV) as dominant bulk defect. From IS & MS, especially the grain boundaries of Sb/Bi=0.5 systems were divided into two types, i.e. sensitive to oxygen and thus electrically active one and electrically inactive intergranular one with temperature.

• 한국태양에너지학회 논문집
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• 제39권1호
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• pp.33-40
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• 2019

Al-doped ZnO (AZO) thin films were synthesized on Si(100) wafers via plasma enhanced metal organic chemical vapor deposition (PE-MOCVD) method using diethyl zinc (DEZ) and N-methylpyrrolidine alane (MPA) as precursors. Effects of Al/Zn mixing ratio, plasma power on the surface morphology, crystal structure, and electrical property were investigated with SEM, XRD and 4-point probe measurement respectively. Growth rate of the film decreased slightly with increasing the Al/Zn mixing ratio, however electrical property was enhanced and resistivity of the film decreased greatly about 2 orders from $9.5{\times}10^{-1}$ to $8.0{\times}10^{-3}{\Omega}cm$ when the Al/Zn mixing ratio varied from 0 to 9 mol%. XRD analysis showed that the grain size increased with increasing the Al/Zn mixing ratio. Growth rate and electrical property were enhanced in a mild plasma condition. Resistivity of AZO film decreased down to $7.0{\times}10^{-4}{\Omega}cm$ at an indirect plasma of 100 W condition which was enough value to use for the transparent conducting oxide (TCO) material.

• 한국전기전자재료학회논문지
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• 제29권8호
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• pp.470-475
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• 2016

In this study, $Zn_xMn_{3-x}O_4$ (x=0.95~1.20) specimens were prepared by using a conventional mixed oxide method. All specimens were sintered in air at $1,200^{\circ}C$ for 12 h and cooled at a rate of $2^{\circ}C/min$ to $800^{\circ}C$, subsequently quenching to room temperature. We investigated the structural and electrical properties of $Zn_xMn_{3-x}O_4$ specimens with variation of ZnO amount for the application of NTC thermistors. As results of X-ray diffraction patterns, all specimens showed the formation of a complete solid solution with tetragonal spinel phase. And, the second phase was observed by the solubility limit of Zn ions in $x{\geq}1.10$ composition. The average grain size was increased from $2.72{\mu}m$ to $4.18{\mu}m$ with increasing the compositional ratio of Zn ion from x=0.95 to 1.20, respectively. $Zn_{1.10}Mn_{1.90}O_4$ specimen showed the minimum electrical resistance of $57.5k{\Omega}$ at room temperature and activation energy of 0.392 eV.

• The Korean Journal of Ceramics
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• 제1권1호
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• pp.13-20
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• 1995

Effects of thermal annealing on the dielectric/piezoelectric properties of $Pb(Zn, Mg)_{1/3}Nb_{2/3}O_3-PbTiO_3$ ceramics (PZMNPT) with Zn/Mg=6/4) were examined across the rhombohedral/tetragonal morphotropic phase boundary (MPB). Both the relative dielectric permittivity ($\varepsilon$r)and the piezoelectric constant($d_33$)/electromechanical coupling constant ($k_p$)were increased by thermal annealing ($800^{\circ}$~$900^{\circ}C$) after sintering at $1150^{\circ}C$ for 1 hr. Based on the dielectric analysis using the series mixing model and the concept of a random distribution of the local Curie points, the observed improvements in the dielectric and piezoelectric properties of PZMN-PT were interpreted in terms of the elimination of PbO-rich amorphous intergranular layers(~1nm) induced by thermal annealing. A concrete evidence of the presence of amorphous grain-boundary layers in the unannealed (as-sintered) specimen was obtained by examining the structure of intergranular region using a TEM.

• Bulletin of the Korean Chemical Society
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• 제32권9호
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• pp.3453-3458
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• 2011

The $Mg_xZn_{1-x}O$ thin films with the various content ratio ranging from 0 to 0.4 were prepared by sol-gel spincoating method. To investigate the effects of content ratio on the structural and optical properties of the $Mg_xZn_{1-x}O$ thin films, scanning electron microscopy (SEM), X-ray diffraction (XRD), and photoluminescence (PL) were carried out. With increase in the content ratio, the grain size of the $Mg_xZn_{1-x}O$ thin films was increased, however, at the content ratio above 0.2, MgO particles with cubic structure were formed on the surface of the $Mg_xZn_{1-x}O$ thin films, indicating that the Mg content exceeded its solubility limit in the thin films. The residual stress of the $Mg_xZn_{1-x}O$ thin films is increased with increase in the Mg mole fraction. In the PL investigations, the bandgap and the activation energy of the $Mg_xZn_{1-x}O$ thin films was increased with the Mg mole fraction.