• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.08a
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• pp.126-129
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• 2003

The electrical properties of a ZnO-based multilayered chip varistor (abbreviated as MLV) were studied as functions of firing condition and the degree of lamination. The fundamental varistor characteristics such as nonlinear coefficient and breakdown voltage were independent of the degree of lamination. As the number of the laminated ceramic sheets increased, however, not only the energy handling capability but also the capacitance and the leakage current which are relevant to delayed response to the voltage surge and the pre-breakdown energy loss, respectively, increased. With the increase of firing temperature between $950^{\circ}C$ and $1150^{\circ}C$, both the capacitance and the leakage current of the MLV increased due mainly to the grain growth of ZnO and the volatilization of $BiO_2O_3$. High performance MLVs with clear electrode pattern were obtained at the firing temperature range of $l000{\sim}1050^{\circ}C$ in this experiment.

• Fire Science and Engineering
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• v.10 no.4
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• pp.3-12
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• 1996

The aim of the present study is to find out the effect of cooling rate on the electrical behavior of ZnO varistors. The microstructure, 1-V characteristics and complex impedance spectra were investigated under the change of cooling rates. It is found that at cooling rate $200^{\circ}$/h, nonlinearity and breakdown voltage reached a maximum value which may show that good intergranular layer is formed as a results of proper cooling rate. Complex Impedance spectras were measured as a function of frequency range 100Hz to 13MHz to determine grain and grainboundary resistance. The semicircles were attributed to the dependence of grain and grainboundary resistance on cooling rates.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.100-100
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• 2009

ZnO 바리스터는 정전기 및 순간적인 surge로부터 전자기기 및 전자회로 등을 보호하기 위해 개발된 전자 세라믹스 소재이다. 최근 전자기기 등의 고속통신 추세에 따라 ZnO 바리스터는 높은 비선형 특성과 함께 보다 낮은 유전율 및 유전손실 특성이 특별히 요구되고 있다. 따라서 본 연구에서는 현재 양산되고 있는 Bi-계와 Pr-계 ZnO 바리스터가 아닌 새로운 조성계를 이용하여 Y 첨가량(0.1~3.0 at%)에 따른 ZnO 바리스터의 전기적 특성과 유전 특성을 살펴보았다. 시편은 일반적인 세라믹 공정에 따라 제조하여 $1200^{\circ}C$에서 3 시간 공기 중에서 소결하였으며, 소결 및 전기적 특성과 유전 특성(밀도, 미세구조, I-V 특성, 유전율, 유전손실, ZnO grain 비저항)은 FE-SEM, Keithley237, Agilent 4294a 및 Agilent 4991a 장비를 사용하여 Y 함량에 따른 ZnO 바리스터의 특성 변화를 고찰하였다. 그 결과, Y이 2.0 at% 첨가한 계의 바리스터 특성이 가장 우수하였다. 보다 구체적으로 살펴보면 다음과 같다. Y 함량이 증가함에 따라 상대밀도는 94~96%로 증가하였으며, 평균입경은 증가하였다. 또한 유전율은 580~215 (at 1 MHz)로 Y 함량이 증가할수록 낮아졌다. 이를 통하여 새로운 바리스터 조성계에서 Y의 첨가 효과에 대하여 논하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.13 no.1
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• pp.53-59
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• 1999

The ceramic capacitor was fabricated by $(Ba_{0.85}Ca_(0.15)TiO_3+ZnO$ + ZnO(from 0.1 to 0.4 mol ratio). The electrical and structural properties of ceramic capacitor for high voltage application was studied in this study. The relative rensity of ceramics capacitor has shown high in all specimen. The grain was a small size from $1.0[\mum]$ to $1.22[\mum]$ and it was increased with ZnO at 0.3 mol ratio. It was stabilized that the temperature coefficient of ceramic capacitor to change temperature had below 100[ppm] at 0.12~10[kHz]. The dielectric reIaxation time was decreased by interface polarization over $110[^{\circ}C]$ and it was increased by space polarization of paraelectric layer below $110[^{\circ}C]$. The insulating layer was increased with ZnO and dielectric constant to voltage was stabilized by 0.1[%].0.1[%].

• Proceedings of the KIEE Conference
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• 1999.11a
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• pp.4-6
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• 1999

We have performed spin-spray ferrite plating of $Fe_{3-x}Zn_xO_4$($X=0.47{\sim}0.97$) films in the temperature region T=85[$^{\circ}C$]. A reaction solution and an oxidizing solution were supplied to a reaction chamber by supply pumps. The Zn composition X in the $Fe_{3-x}Zn_xO_4$ Film increases as the content of $ZnCl_2$ increase, from X=0.47 at O.05[g/l] to X=0.97 at 0.15[g/l]. All the films are polycrystalline with no preferential orientation, and the magnetization exhibits no definite anisotropy. Grain size in the films increases as X increases, reaching 0.98[${\mu}m$] at X=0.97.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.51 no.2
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• pp.82-86
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• 2002

A series of $Ni_xZn_yFe_{3-x-y}O_4$ films were prepared by spin-spray ferrite plating on glass substrates from aqueous solution at $90[^{\circ}C]$. The magnetic properties in terms of contents of Ni and Zn in the plated films are presented. All the films are polycrystalline with spinel structure. At x+y=0.58, the film presents preferential orientation. As composition of y in the films increases grain size and void in the films increases, while saturation magnetization and coercive force of the films decrease.

• Korean Journal of Materials Research
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• v.18 no.2
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• pp.84-91
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• 2008

The effects of the deposition and annealing temperature on the structural, electrical and optical properties of Ag doped ZnO (ZnO : Ag) thin films were investigated. All of the films were deposited with a 2wt% $Ag_2O-doped$ ZnO target using an e-beam evaporator. The substrate temperature varied from room temperature (RT) to $250^{\circ}C$. An undoped ZnO thin film was also fabricated at $150^{\circ}C$ as a reference. The as-grown films were annealed in temperatures ranging from 350 to $650^{\circ}C$ for 5 h in air. The Ag content in the film decreased as the deposition and the post-annealing temperature increased due to the evaporation of the Ag in the film. During the annealing process, grain growth occurred, as confirmed from XRD and SEM results. The as-grown film deposited at RT showed n-type conduction; however, the films deposited at higher temperatures showed p-type conduction. The films fabricated at $150^{\circ}C$ revealed the highest hole concentration of $3.98{\times}1019\;cm^{-3}$ and a resistivity of $0.347\;{\Omega}{\cdot}cm$. The RT PL spectra of the as-grown ZnO : Ag films exhibited very weak emission intensity compared to undoped ZnO; moreover, the emission intensities became stronger as the annealing temperature increased with two main emission bands of near band-edge UV and defect-related green luminescence exhibited. The film deposited at $150^{\circ}C$ and annealed at $350^{\circ}C$ exhibited the lowest value of $I_{vis}/I_{uv}$ of 0.05.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.2
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• pp.74-80
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• 2017

This study focuses on the effects of doping $Zn_2BiVO_6$ and $Co_3O_4$ on the sintering and electrical properties of ZnO; where, ZZ consists of 0.5 mol% $Zn_2BiVO_6$ in ZnO, and ZZCo consists of 1/3 mol% $Co_3O_4$ in ZZ. As ZnO was sintered at about $800^{\circ}C$, the liquid phases, which are composed of $Zn_2BiVO_6$ and $Zn_2BiVO_6$-rich phases, were found to be segregated at the grain boundaries of sintered ZZ and ZZCo, respectively, which demonstrates that $V_o^{\cdot}$(0.33~0.36 eV) are formed as dominant defects according to the analysis of admittance spectroscopy. As $Co_3O_4$ is doped to ZZ, the resistivity of ZnO decreases to ~38%, while donor density ($N_d$), interface state density ($N_t$), and barrier height (${\Phi}_b$) increase twice higher than those of ZZ, according to C-V characteristics. This result harbingers that ZZCo and its derivative compositions will open the gate for ZnO to be applied as more progressive varistors in the future, as well as the advantageous opportunity of manufacturing ZnO chip varistors at lower sintering temperatures below $900^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.6
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• pp.719-725
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• 1995

ZST powders were synthesized by coprecipitation of (Zr4+, Ti4+)-hydroxide in the presence of SnO2 particles. Zn(NO3)2 was used as a sintering additive, and according to the adding sequence, sintering and dielectric properties were investigated. Sintered densities of ZST prepared by adding Zn(NO3)2 before calcination were a little higher than those added after calcination, and dielectric properties of the specimen added by Zn(NO3)2 after calcination were better (sintered at 125$0^{\circ}C$/2 h ; Q$\times$f(GHz)=49, 000, $\varepsilon$r=41) than before calcination (Q$\times$f(GHz)=42, 000, $\varepsilon$r=39.5). Through the observation of TEM, it was identified that the cause was due to the difference of the degree of Zn2+ diffusion into grains. With increasing sintering time from 2 to 8 hrs, grain size was doubled and dielectric properties were somewhat deteriorated.

• Journal of Magnetics
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• v.20 no.3
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• pp.246-251
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• 2015

This study was aimed to study the effect of Zn content on the hyperfine parameters and the structural variation of $Ni_{1-x}Zn_xFe_2O_4$ for x = 0, 0.2, 0.4, 0.6, and 0.8. To achieve this, a sol-gel route was used for the preparation of samples and the obtained ferrites were investigated by X-ray diffraction, scanning electron microscopy, and $M{\ddot{o}}ssbauer$ spectroscopy. The formation of spinel phase without any impurity peak was identified by X-ray diffraction of all the samples. Moreover, the estimated crystallite size by X-ray line broadening indicates a decrease with increasing Zn content. This result was in agreement with the scanning electron microscopy result, indicating the reduction in grain growth with further zinc substitution. The room-temperature $M{\ddot{o}}ssbauer$ spectra show that the hyperfine fields at both the A and B sites decreased with increasing Zn content; however, the rate of reduction is not the same for different sites. Moreover, the best fit parameter showed that the quadrupole splitting values of B site increased from the pure nickel ferrite to the sample with x = 0.8.