• Title, Summary, Keyword: Semiconducting Grain boundary

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Grain Boundary Chemistry and Electrical Characteristics of Semiconducting $SrTiO_3$ Ceramics Synthesized from Surface-Coated Powders (표면 코팅된 분말을 이용하여 제조된 반도성 $SrTiO_3$ 소결체의 입계화학과 전기적 특성)

  • Park, Myung-Beom;Kim, Chong-Don;Heo, Hyun;Cho, Nam-Hee
    • Journal of the Korean Ceramic Society
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    • v.36 no.11
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    • pp.1252-1260
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    • 1999
  • The defect chemistry and electrical characteristics of the grain boundaries of semiconducting SrTiO3 ceramics synthesized with wet-chemically surface-coated powders were investigated. The starting powders were separated into groups of 1-10${\mu}{\textrm}{m}$ 10-20${\mu}{\textrm}{m}$ etc by sedimentation and sieving methods. Na+ ions were absorbed on the powder surfaces by wet chemical-treatment method. The width of the grain boundary ranged up to several nm and the intergranular materials was amorphous. The additives coated on the surface of the powders were observed to be present at the grain boundaries of the ceramics. The diffusion depth of the additives into grains was about 30nm for the SrTiO3 ceramics synthesized with 5w/o coated materials, The threshold voltage grain boundary resistance and boundary potential barrier of the ceramics increased from 0.67V/cm 2.27k$\Omega$ and 0.05eV to 80.9V/cm 13.0k$\Omega$ 1.44eV with increasing the amount of the additives from 0 to 5 w/o respectively .

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Electrical and Chemical Characteristics of the Grain Boundaries of Semiconducting $BaTiO_3$ Ceramics Prepared with Surface-Coated Powders (표면 코팅된 분말을 이용하여 제조된 반도성 $BaTiO_3$ 소결체의 입계 화학 및 전기적 특성)

  • 박명범;김정돈;조남희
    • Journal of the Korean Ceramic Society
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    • v.37 no.4
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    • pp.338-344
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    • 2000
  • Grain boundary chemistry and electrical characteristics of polycrystalline BaTiO3 ceramics, which were prepared with sol-gel surface-coated semiconducting powders, were investigated. Mn ions were coated on the powder surface by sol-gel coating-techniques. The additives coated on the surface of the powders were observed to be present near the grain boundaries of the ceramics. The ceramics exhibit the PTCR characteristics with a resistivity jump ratio(Pmax/Pmin) of about 2$\times$103. With raising the temperature from room temprature to 20$0^{\circ}C$, the oxidation state of the Mn ions varied from Mn3+ to Mn2+ in the coating layers. Near the grain boundaries an excessive negative charge layer of about 20nm was formed.

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PTCR Effects of Semiconducting (Ba1-xPbx)TiO3 Ceramics with 0.5 mol% Pb5Ge3O11 (0.5 mol% Pb5Ge3O11가 첨가된 반도성 (Ba1-xPbx)TiO3 세라믹스의 PTCR 효과)

  • 윤상옥;정형진;윤기현
    • Journal of the Korean Ceramic Society
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    • v.28 no.7
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    • pp.525-530
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    • 1991
  • The effects of 0.15mol% Y2O3 doped semiconducting (Ba1-xPbx)TiO3 ceramics with 0.5 mol% Pb5Ge3O11 as sintering additives have been investigated as function of Pb contents (from 0.05 mol to 0.3 mol) and sintering temperatures (from 1050$^{\circ}C$ to 1200$^{\circ}C$). As the Pb content increases in the (Ba1-xPbx)TiO3 system, the size and resistance of the grain increase but the capacitance of the grain boundary decreases due to the formation of liquid phase during the sintering. And with increasing the sintering temperatures, the resistance of the grain decreases but the capacitance of the grain boundary increases. The PTCR effects decrease with increasing the Pb content and the sintering temperature.

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Electric equivalent circuit of $SrTiO_3$-based varistor ($SrTiO_3$ 바리스터의 전기적 등가회로)

  • Kang, Dae-Ha;Roh, Il-Soo
    • Journal of Advanced Marine Engineering and Technology
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    • v.30 no.8
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    • pp.907-918
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    • 2006
  • In this study capacitance and dielectric loss factor were measured with low-voltage signal and the simulation of equivalent circuits for the data was conducted. As the result it was shown that the equivalent circuit model considered the grain-boundary structure with semiconducting layer, dielectric layer and depletion layer was well approximated with the observed data. Various parameters were determined by a optimum curve-fitting method and could be used to analyze the characteristics of varistor. It also seems that the proposed equivalent circuit model will be adopted for other BL type varistors.

Electrical Characteristics of (BaSr)TiO3-based PTCR Devices under the Electric Field

  • Lee, Joon-Hyung;Cho, Sang-Hee
    • Journal of the Korean Ceramic Society
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    • v.39 no.1
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    • pp.16-20
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    • 2002
  • Semiconducting (Ba.Sr)TiO$_3$ceramic device, which shows the PTCR effect, has been usually used as a current limiter. In this case, the device should endure the condition under the high electric field. In this study, the dynamic electrical properties of the PTCR device under high voltage has been evaluated. Two different formulated powders were used and the sintered bodies exhibited the different grain size and porosity. The wide range of characterization such as complex impedance spectroscopy, microstructure, I-V characteristics and voltage dependence of resistivity of the samples were performed. The PTCR effect of the specimen containing coarse grains was very sensitively dependent on the AC electric field, showing that it was inversely pro-portional to the grain boundary potential barrier. The withstanding voltage was proportional to the potential barrier of grain boundary.

A Study on the Electrical Properties of Polycrystalline ZnO Film (다정질(多晶質) ZnO 필름의 전기적(電氣的) 성질(性質)에 대한 일고찰(一考察))

  • Sung, Yuong-Kwon;Rhie, Dong-Hee;Choi, Bok-Gil
    • Proceedings of the KIEE Conference
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    • pp.355-358
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    • 1988
  • Polycrystalline transparent semiconducting zinc oxide film has been characterized for their electrical properties. The conductivity of the film could be increased by approximately five times of magnitude by annealing it in hydrogen at 400 C. The electrical properties measured on the temperature range of RT to 120 K give support well to the model which depicts the importance of the grain boundary effects on the electrical conduction of zinc oxide film.

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A study on the dielectric and electrical conduction properties of$(Sr_{1-x}.Ca_x)TiO_3$ grain boundary layer ceramics ($(Sr_{1-x}.Ca_x)TiO_3$입계층 세라믹의 유전 및 전기전도특성에 관한 연구)

  • 최운식;김충혁;이준웅
    • Electrical & Electronic Materials
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    • v.8 no.5
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    • pp.611-618
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    • 1995
  • The (Sr$_{1-x}$ .Ca$_{x}$)TiO$_{3}$+0.6[mol%]Nb$_{2}$O$_{5}$ (0.05.leq.x.leq.0.2) ceramics were fabricated to form semiconducting ceramics by sintering at about 1350[.deg. C] in a reducing atmosphere(N$_{2}$ gas). Metal oxides, CuO, was painted on the both surface of the specimens to diffuse to the grain boundary. They were annealed at 1100 [.deg. C] for 2 hours. The 2nd phase formed by thermal diffusing from the surface lead to a very high apparent dielectric constant. According to increase of the frequency as a functional of temperature, all specimens used in this study showed the dielectric relaxation, and the relaxation frequency was above 106 [Hz], it move to low frequency with increasing resistivity of grain. The specimens showed three kinds of conduction mechanisms in the temperature range 25-125 [.deg. C] as the current increased: the region I below 200 [V/cm] shows the ohmic conduction. The region rt between 200 [V/cm] and 2000 [V/cm] can be explained by the Poole-Frenkel emission theory, and the region III above 2000 [V/cm] is dominated by the tunneling effect.fect.

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