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  • 1
    Electronic Resource
    Electronic Resource
    Aging study of nickel-copper-manganite negative temperature coefficient thermistors by thermopower measurements (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 4705-4709 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ceramic nickel-copper-manganite based negative temperature coefficient thermistors are unstable under thermal constraint, which increases the resistivity of these devices. This unstability can be reduced by the addition of a small amount of barium. These ceramics have a spinel structure, and the conduction takes place by a hopping process involving [Mn3+]/[Mn4+] octahedral ions. This study by the use of thermopower measurements points out that the resistivity change under thermal constraint is principally due to the disproportionation of [Mn3+]/[Mn4+] ions in the octahedral sites. Furthermore, it seems that some nickel ions migrate from octahedral to tetrahedral sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.352076
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Low frequency and low temperature behavior of ZnO-based varistor by ac impedance measurements (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 4046-4052 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper reports on an original work on the study of the behavior of ZnO-based varistor by ac impedance measurements. The measurements of complex impedance response to small ac signals applied to samples have been achieved in the frequency range 10−3–7×106 Hz and a temperature range −196–145 °C. In the temperature range below −120±10 °C, a complete semicircular relaxation phenomenon has been observed, which is in good agreement with the Debye model. In the temperature range above −120±10 °C, the appearance of the depression angle θ may arise from the heterogeneity of the barriers of the ceramic varistor. A Cole–Cole distribution function of the relaxation time constants was used to characterize the response of the ceramic device as a function of temperature. No observable influence in the response was introduced by either the space charge or the electrode. Using the leakage resistance measurements from the complex plane, two values of the activation energies were observed; 0.36±0.02 eV and 0.01±0.001 eV. Similarly, the boundary layer equivalent capacitance measurements detect two other energy levels: 0.06±0.005 eV and about 0 eV.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348414
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Aging of zinc oxide varistors subjected to partial discharges in sulfur hexafluoride (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 1036-1040 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The behavior of zinc oxide varistors subject to partial discharges in sulfur hexafluoride is studied with respect to their protective coating (glass and epoxy resin). Sulfur hexafluoride (SF6) is used as an insulating medium for the electrical equipment because of its high dielectric strength and good heat transfer properties. The decomposition of SF6 and residual impurities can considerably influence the varistor current-voltage characteristics essentially in the ohmic region. An analysis of the phenomenon shows that the degradation is due to a conducting deposit around the varistors and a physical corrosion of the coating.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347419
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Electrical characteristics of zinc oxide varistors subjected to hydrostatic pressure (1985)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 57 (1985), S. 5535-5538 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This paper presents the changes of electrical characteristics in zinc oxide varistors subjected to hydrostatic pressure up to 4 kbar. Electrical measurements have been carried out with pressurized samples. Beyond 1 kbar, the leakage current increases exponentially with pressure as described by the relationship IF=P7,4. This leads to a decrease, by a factor of 2, of the nonlinear coefficient. In spite of choosing a different experimental approach and different material compounds, our results are in very good agreement with those already published.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.334834
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Electrical characteristic degradation of ZnO varistors subjected to partial discharges (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4048-4050 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Zinc oxide is a polycrystalline ceramic having nonlinear current-voltage characteristics. This specific property allows it to be used as varistors. When these components are set in medium- or high-voltage lightning arresters, they may be subjected to partial discharges. The objectives of this study were to determine the action of partial discharge parameters on the I(V) characteristic degradation. Varistor samples under test were made with a standard process. They were metallized on both ends and were either covered with an insulating layer or not. The results obtained from bare samples in dry and wet air and at room temperature showed an important modification of the I(V) characteristic in the ohmic region with a large increase of leakage current.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343330
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Different "single grain junctions'' within a ZnO varistor (1987)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 61 (1987), S. 1562-1567 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The experimental part of this work describes a new method to determine the electrical characteristics of a single ZnO varistor grain-to-grain junction. The experimental results are described in statistical terms because each single barrier has been found to present its own electrical characteristics. There are "good'' and "bad'' barriers. On the basis of our experimental observations, we present an original approach to describing the current-voltage characteristics of ZnO varistors from the characteristics of individual junctions (series or parallel models). Finally, this work demonstrates that a ZnO sample having a low thickness and a large nonlinear coefficient value requires only "good'' junctions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.338091
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Ageing study of NTC thermistors by thermopower measurements
    Amsterdam : Elsevier
    Sensors and Actuators A: Physical 33 (1992), S. 119-122 
    Details
    ISSN: 0924-4247
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Electrical Engineering, Measurement and Control Technology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0924-4247(92)80241-T
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