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  • American Institute of Physics (AIP)  (5)
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  • 1
    Electronic Resource
    Electronic Resource
    Electrical and thermal properties of a varistor at cryogenic temperatures (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4223-4228 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A ZnO-based varistor composition has been found whose I-V characteristic is essentially unaffected by temperature (4.2–300 K) or intense magnetic fields at 4.2 K (up to 10 T). Electrical measurements are reported at various temperatures for current densities in the range 10−11–10−3 A/cm2 . Specific-heat and thermal conductivity data are reported at 1.7–300 K. The specific heat below 10 K and above 100 K is dominated by defect modes, and the data can be understood based on simple defect models. The thermal conductivity displays a broad maximum at about 80 K (0.65 W cm−1 K−1 ), and it is concluded that the defect modes do not carry heat. The small temperature dependence of the prebreakdown conductivity is found to be in excellent agreement with a variable-range-hopping model, suggesting that this composition is just above the percolation threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341288
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  • 2
    Electronic Resource
    Electronic Resource
    Dielectric composites incorporating enthalpy stabilization for NbTi windings (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 2729-2735 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Composites of ceramic powders in epoxies appropriate for both insulating and impregnating NbTi windings are studied. Specific heat, thermal conductivity, thermal contraction, and magnetocaloric measurements on composites are presented. Thermal contractions well matched to copper are found, and thermal shock resistance is greatly enhanced. Enthalpies, 4.2–6 K, range up to 80 mJ cm−3 and are 20–50 times larger than that of the pure epoxies. The thermal group parameter, η=(κρC)1/2, is 2 1/2 –4 times larger than that for epoxy (data are given for magnetic field strengths up to 8 T). An interesting magnetocaloric stabilization mechanism is found: on up-ramp, a magnetocaloric enthalpy ≤7.6 mJ cm−3 is available for stabilization via adiabatic-magnetization cooling. Results are not specific to the epoxies used but apply to composites with any amorphous matrices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.341615
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  • 3
    Electronic Resource
    Electronic Resource
    Low-temperature dielectric properties of SrTiO3 glass-ceramics (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 2069-2080 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-temperature dielectric properties of strontium titanate aluminosilicate glass-ceramics, in which perovskite SrTiO3 is the primary crystalline phase, have been investigated. These glass-ceramics exhibited dielectric constant peaks at temperatures below 100 K; the magnitude of these peaks, along with their frequency and temperature dependencies, were strongly dependent on the crystallization conditions. In heavily crystallized glass-ceramics, two low-temperature, relaxation-type loss mechanisms were identified, at temperature ranges near 50 and 100 K. The magnitude of the dielectric loss peak increased with increasing frequency for the lower temperature (50 K) mechanism and the magnitude of the loss peak decreased with increasing frequency for the higher temperature (100 K) mechanism. Arrhenius activation energies were calculated to be 0.054 and 0.17 eV for the lower and higher temperature loss mechanisms, respectively. The higher temperature loss mechanism was further analyzed by the Cole–Cole method, and a relaxation strength of 41 was calculated. It was proposed that the dielectric constant and loss peaks were related to ferroic phenomena occurring in the SrTiO3 phase, caused by interactions of the SrTiO3 with the glass-ceramic matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337211
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  • 4
    Electronic Resource
    Electronic Resource
    Calibration scheme for Allen–Bradley resistors, 4.2–100 K (1988)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 59 (1988), S. 2505-2507 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Based on measured R–T data for ten tempered Allen–Bradley resistors (BB, (1)/(8) W, 1 kΩ), a four-point-calibration scheme is described that yields ΔT/T≤0.5% (≤0.8%, 55–65 K) in the range 4.2–100 K. The procedure involves three successive approximations to the equation log R=A+BT−P.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1139890
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  • 5
    Electronic Resource
    Electronic Resource
    Quantum-ferroelectric pressure sensor for use at low temperatures (1985)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 56 (1985), S. 1913-1916 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A small, multilayer capacitance sensor (∼70 mm3) for measuring pressure over a broad range at low temperatures is described. The dielectric material is a quantum ferroelectric in the (Cd, Pb)2(Nb, Ta)2 O7 ceramic system, and the reciprocal capacitance varies linearly with pressure into the kilobar region. The average sensitivity of the devices studied is 151 pF/kbar, and the sensor is essentially independent of both intense magnetic fields and temperature below 10 K. A calibration for the slight magnetic field effect is given, and the sensor is dielectrically stable at helium temperatures. A one-point pressure calibration is estimated to be reliable to 〈±0.1%, and pressure changes in the millibar range can be resolved if certain precautions are taken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1138444
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