• 한국세라믹학회지
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• 제19권4호
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.

• 반도체디스플레이기술학회지
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• 제4권4호
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• pp.1-4
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• 2005

The chemical composition and uniaxial compressive stress are varied to observe their effect on the current-voltage characteristics of ZnO based ceramics. The variation of chemical composition produces two kinds of ceramics showing ohmic and nonohmic current-voltage characteristics. The current at a fixed voltage increased with the increase of the compressive stress for both ohmic and nonohmic ceramics. Ceramics showing nonohmic behavior exhibit better reversible return of current-voltage curve when the applied compressive stress is removed from the ceramics than those showing ohmic behavior do. We found an appropriate chemical composition showing linear relation between current and stress at a fixed voltage. The ceramic materials with an appropriate chemical composition can be used as a potential sensing material in pressure sensors.

• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.40-47
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• 1995

Electrical properties of ZnO ceramics based on Bi oxide was investigated in relation to sintering temperature. In the temperature range >$1150^{\circ}C$ to >$1350^{\circ}C$ the grain size increased from 9.mu.m to 20.mu.m when the sintering temperature was raised. The leakage current in the low voltage range increased as the potential barrier decreases, which is caused by increasing the grain size at high temperature. The dielectric characteristics of the ZnO ceramics was also affected by sintering temperature. Large dielectric constant was attributed, to the grainboundary layer of polycrystalline ZnO ceramics and decreasing grainboundary width. The variation of breakdown voltage with sintering temperature was attributed to the change of the donor concentration in the ZnO grain and grain size. The results showed that breakdown voltage increased decreasing grain size and donor concentration. Nonohmic coefficient was associated with the lower breakdown voltage per grainboundary layer due to the grain growth and higher donor concentration.

• 한국세라믹학회지
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• 제17권3호
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• pp.133-140
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• 1980

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to sintering temperature and additive content. The kinds of additives used were basic additives ($Bi_2O_3$, $BaCO_3$, $MnCO_3$, $Cr_2O_3$) and $KNO_3$ Especially this study has focused on the effects of $KNO_3$ in ZnO ceramics with basic additives. SEM studies indicated that microstructures of ZnO, $KNO_3$ and basic additives showed homogenuous grain size in comparison to ZnO and basic additives compounds. The nonohmic exponent ($\alpha$) in ZnO, $KNO_3$ and basic additives component were measured as high as 40.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 D
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• pp.1692-1695
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• 1999

The nonohmic characteristics of ZnO-$Pr_6O_{11}$-CoO-based ceramic varistor doped with $Dy_2O_3$ in the range $0.0\sim2.0mol%$ sintered at $1300^{\circ}C$ and $1350^{\circ}C$ were investigated. 98.5 ZnO-$0.5Pr_6O_{11}$-1.0CoO varistor sintered at $130^{\circ}C$ exhibited higher nonlinear coefficient of 36 than the established Pr-based varistor. The four-component-system varistor such as 96.5 ZnO-$0.5Pr_6O_{11}$-1.0CoO-$2.0Dy_2O_3$ exhibited very highly nonohmic characteristics, which has nonlinear coefficient of 53.9. 98.5ZnO-$0.5Pr_6O_{11}$-1.0CoO varistor sintered at $1350^{\circ}C$, in contrast with that of $1300^{\circ}C$, exhibited approximately ohmic characteristics but nonlinear coefficient of varistor doped with 0.5mol% $Dy_2O_3$ showed higher nonlinear coefficient of probably 35. Consequently, it can be confirmed that $Dy_2O_3$ acted as additive of improvement on nonlinear coefficient. It is estimated that $Dy_2O_3$ will be used as additive of improvement on nonlinear coefficient to develop a goof ZnO varistor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.372-374
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• 1987

• E2M - 전기 전자와 첨단 소재
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• 제7권2호
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• pp.138-144
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• 1994

Electrical conduction phenomena of $C_{22}$-quinolium(TCNQ) Langmuir- Blodgett(LB) films are reported through a study of current-voltage(I-V) characteristics along a perpendicular direction. The I-V characteristics were investigated by applying a step or a pulse voltage to the specimen as well as changing temperatures in the range of 20-250[.deg. C] It show an ohmic behavior in low-electric field, and a nonohmic behavior in high-electric field. This nonohmic behavior has been interpreted in terms of a conduction mechanism of space-charge limited current and Schottky effect. When the electric field is near the strength of 10$_{6}$ V/cm, there occur anomalous phenomena similar to breakdown. When step or pulse voltage is applied, the breakdown voltage shifts to the higher one as the step or pulse time width becomes shorter. To see the influence of temperature, current was measured as a function of temperature under the several bias voltages, which are lower than that of breakdown. It shows that the current increases to about 103 times near 60-70[.deg. C], and remains constant for a while up to around 150[.deg. C] and then suddenly drops. We have also performed a DSC(differential scanning calorimetry) measurement with $C_{22}$-quinolium(TCNQ) powder in the range of 30-300[.deg. C]. These results imply that the anomalous phenomena occuring in the high electric field are caused by the electrical and internal thermal effect such as a joule heating.ating.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 B
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• pp.1193-1196
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• 1993

Electrical properties of $C_{22}$-Quinolium(TCNQ) Langmuir-Blodgett(LB) films are reported depending on a type of applied voltage on a type of applied voltage and temperature. A conductivity was identified to be anisotropic with a ratio of ${\sigma}||/{\sigma}{\bot}{\simeq}10^7$ at room temperature. The I-V characteristics along the film surface direction show an ohmic behavior up to a few hundred volts. But the I-V characteristics in the vertical direction display an ohmic behavior for low-electric field, and a nonohmic behavior for high-electric field. This nonohmic behavior has already been interpreted as a conduction mechanism of space-charge limited current and Schottky effect near the electric-field strengh of $10^6$ V/cm. When the electric field exceeds further, there is anormalous phenomia similiar to breakdown. From the study of I-V characteristics with the application of step or pulse voltage, we have found that the breakdown voltage shifts to higher one as the step or pulse interval becomes shorter. These results indicate that the breakdown is due to both electrical and thermal effect. To see the infulence of temperature, current was measured as function of temperature with several bias voltages, which are lower than that of breakdown. It shows that the current increases about 3 orders of magnitude near $60{\sim}70^{circ}C$, and remains constant for a while up to $140^{\circ}C$ and then suddenly drops. Arahidic acid was used to cmpare with $C_{22}$-Quinolium(TCNQ) LB films.

• 한국응용과학기술학회지
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• 제23권3호
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• pp.238-242
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• 2006

Polyimide is a well-known organic dielectric material, which has not only high chemical and thermal stability but also good electrical insulating and mechanical properties. In this research, the electric conduction mechanism of PI Ultra-Thin Films was investigated at room temperature. At low electric field, ohmic conduction $(I{\propto}V)$ was observed and the calculated electrical conductivity was about $4.23{\times}10^{-15}{\sim}9.81{\times}10^{-15}\;S/cm$. At high electric field, nonohmic conduction $(I{\propto}V^2)$ was observed and the conduction mechanism was explained by space charge limited region effect. The dielectric constant of PI Ultra-Thin Films was about 7.0.

• 한국세라믹학회지
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• 제26권4호
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• pp.487-492
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• 1989

The microstructure and electrical properties of ZnO-Bi2O3 system with Bi2O3(0.5~5mol%) content have been investigated in relatin to sintering temperature and atmosphere. The grain size of ZnO increases sharply with Bi2O3(0.5~5mol%) content, but over 0.5mol% Bi2O3 increased less rapidly when sintered at 120$0^{\circ}C$. Electrical characteristics varied with sintering atmosphere and air-sintered conditions showed comparatively lower nonlinear exponents than the double-crucible conditions. Calculated barrier voltage was about 1.7V.