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  • 2000-2004  (1)
  • 1985-1989  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 3850-3856 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Polycrystalline barium titanate that has been doped to give a positive temperature coefficient of resistance (PTCR) effect is an inhomogeneous material electrically. Analysis of ac impedance data using the complex impedance plane representation gives the dc resistance of PTCR ceramics. By additional use of the complex electric modulus formalism to analyze the same data, the inhomogeneous nature of the ceramics may be probed. This reveals the presence of two, sometimes three elements in the equivalent circuit. Grain-boundary and bulk effects may be distinguished from capacitance data: grain-boundary effects have temperature-independent capacitances, whereas bulk effects show a capacitance maximum at the Curie point and Curie–Weiss behavior above the Curie point. Both grain-boundary and bulk effects appear to contribute to the PTCR effect. These results reveal limitations in current theories of the PTCR effect.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 53 (1988), S. 2624-2629 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 7 (1988), S. 823-824 
    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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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 35 (2000), S. 4823-4826 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Pore reduced cements (PRC) are used as a high resistance matrix for ac impedance studies on cement systems with impedance data being collected over a range of temperatures (−60 to ca. 20 °C) and electrode contact pressures (up to 72 MPa). The results show the presence of two arcs in the complex impedance plots, Z *, at all measured temperatures. The low frequency (LF) arc is attributed to an ineffective electrical contact at the sample/electrode interface and although the high frequency (HF) arc is associated with the cement, its characteristics are also influenced by the contact resistance. Arrhenius plots show the activation energy for conductivity associated with the LF and HF elements to be the same indicating similar conduction mechanisms. Low and high frequency arcs are resolved only by the different geometric factors (conductive volumes) associated with the ineffective contact and the bulk cement specimen.
    Type of Medium: Electronic Resource
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