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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 88 (2000), S. 6545-6548 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical characteristics of highly dense SnO2 ceramic varistors are believed to be caused by the existence of potential barriers at the grain boundary. A complex plane analysis technique (to eliminate the influence of trapping activity associated with the conductance term observed via depression angle of a semicircular relaxation in the complex capacitance plane), allied with an approached Mott–Schottky model, are used to demonstrate that the potential barriers at the grain boundary are Schottky-type barriers in SnO2 varistors such as those observed in the traditional ZnO varistor. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 84 (1998), S. 3700-3705 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electrical properties of tin oxide varistors doped with CoO, Nb2O5, and Cr2O3, were investigated using the impedance spectroscopy technique with the temperature ranging from 25 to 400 °C. The impedance data, represented by means of Nyquist diagrams, show two time constants with different activation energies, one at low frequencies and the other at high frequencies. These activation energies were associated with the adsorption and reaction of O2 species at the grain boundary interface. The Arrhenius plots show two slopes with a turnover at 200 °C for both the higher and lower frequency time constants. This behavior can be related with the decrease of minor charge carrier density. The barrier formation mechanism was associated with the presence of CrSn⋅ at the surface, which promotes the adsorption of the O′ and O″ species which are in turn proposed as being responsible for the barrier formation. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 3416-3419 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ferroelectric SrBi2Ta2O9 thin films on Pt/Ti/SiO2/Si were successfully synthesized by the modified polymeric precursor method. The films were deposited by spin coating and crystallized by rapid thermal annealing in a halogen lamp furnace, followed by postannealing at temperatures ranging from 700 °C to 800 °C in an oxygen atmosphere. Microstructural and phase evaluations were followed by x-ray diffraction and atomic force microscopy. The films displayed spherical grain structures with a superficial roughness of approximately 3–6 nm. The dielectric constant values were 121 and 248 for films treated at 700 °C and 800 °C, respectively. The P–E curve showed a voltage shift toward the positive side, which was attributed to crystallization under the halogen illumination. The remanent polarization (2Pr) and coercive field (Ec) were 7.1 μC/cm2 and 113 kV/cm, and 18.8 μC/cm2 and 93 kV/cm for the films treated at 700 °C and 800 °C, respectively. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6007-6014 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes the admittance-frequency feature of a class of SnO2⋅CoO-based polycrystalline ceramics with high nonlinear current–voltage characteristics (nonlinear coefficients above 50). Broad relaxation peaks caused by the presence of deep trap states were characterized based on the admittance response of different systems doped with La2O3, Pr2O3, and CeO2. The calculation of the energy of this deep trap level revealed not only that all the compositions share the same value but also that this value could be attributed to an oxygen vacancy or to CoSn[partial lengthening] like defects. The values of barrier height and density of states obtained from a capacitance–voltage analysis are in good agreement with the nonlinear coefficients. The highest nonlinear coefficients are found in compositions with greater barrier height values and higher density of deep trap states at the grain boundary interface. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 48-50 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A model is proposed here to explain how the chemical features of metal oxide varistors can alter their nonohmic physical behavior, based on nonohmic similarities in the electrical properties of ZnO- and SnO2-based varistors. The proposed model explains the electrical properties of ZnO- and SnO2-based varistors before and after thermal treatments in oxygen- and nitrogen-rich atmospheres, which cause similar changes in the nonohmic feature of these polycrystalline ceramics with greatly differing chemical compositions and microstructures. The model is based on the key role that oxygen plays in varistor grain boundaries, independently of the type of ceramic system (ZnO-, SnO2- or even SrTiO3-based varistors) involved. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Inc
    Journal of the American Ceramic Society 88 (2005), S. 0 
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: We performed a comparative study of electrical and thermal properties of ZnO- and SnO2-based varistor. The electrical properties of commercial ZnO-based varistor are equivalent to that found in SnO2-based varistor system. In spite of this, the SnO2 showed a thermal conductivity higher than commercial samples of ZnO-based varistor, which allied with its simpler microstructure and lower dopant concentration is a remarkable result that point out to the use of this system to compete commercially with ZnO-based varistor devices.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The non-ohmic properties of the 98.95% SnO2 + 1.0%,CoO + 0.05%,Nb2O5 (all in mole%) system, as well as the influence of sintering temperature and atmosphere on these properties, were characterized in this study. The maximum non-linear coefficient (α = 32) was obtained for a sintering temperature of 1300°C in an oxygen atmosphere and this maximum is associated with the presence of O in SnO2 grain boundaries, as interface defects. Experimental results also indicate thermionic-type conduction mechanisms, which are associated with the potential barrier of Schottky or Poole–Frenkel types.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 9 (1998), S. 159-165 
    ISSN: 1573-482X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The non-linear electrical properties of CoO-doped and Nb2O5-doped SnO2 ceramics were characterized. X-ray diffraction and scanning electron microscopy indicated that the system is single phase. The electrical conduction mechanism for low applied electrical field was associated with thermionic emission of the Schottky type. An atomic defect model based on the Schottky double-barrier formation was proposed to explain the origin of the potential barrier at the ceramic grain boundaries. These defects create depletion layers at grain boundaries, favouring electron tunnelling at high values of applied electrical field. © 1998 Chapman & Hall
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Abstracts are not published in this journal
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 14 (1995), S. 692-694 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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