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  • 1
    Electronic Resource
    Electronic Resource
    A quantitative analysis of the thermoelectric power measurements on composite Al-Ge films (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7441-7445 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermoelectric power (Seebeck coefficient) measurements at room temperature have been made on composite Al-Ge films for aluminum volume fractions ranging from 20% to 100%, the metal-insulator transition being at about 55%. These measurements were motivated to test theoretical predictions recently suggested by Bergman and Levy. The electrical conductivity, substituted in their equation, was obtained both by direct measurements and an effective media equation while the thermal conductivity was obtained from two different effective media equations. The agreement between the theoretical and experimental results support the correctness both of their theory and the effective media equations used.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353987
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  • 2
    Electronic Resource
    Electronic Resource
    A quantitative analysis of the volume fraction dependence of the resistivity of cermets using a general effective media equation (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 195-199 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results analyzed, all from previous work, are for W-Al2O3 (as prepared and annealed; 300 K) and Ni-SiO2 (4.2 and 291 K). These results, in which the resistivity changes from 10−5 to 107 Ω cm as the metal volume fraction is varied, can all be quantitatively fitted to a general effective media (GEM) equation. The GEM equation was developed as an interpolation between Bruggeman's symmetric and asymmetric media equations for ellipsoidal grains. It has four parameters. The conductivities of the low [σ(lo)] and high [σ(hi)] conductivity components, fc=(1−cursive-phic), where cursive-phic is the critical (percolation) volume fraction of the σ(hi) component and t is an exponent. f is the volume fraction of the dielectric or σ(lo) component. As, when σ(lo)=0 or σ(hi)=∞ the GEM equation reduces to the percolation equations, it can also be regarded an interpolation formula between these equations. The W-Al2O3 (as prepared; 300 K) and Ni-SiO2 (291 K) results need a five-parameter fit as ρ(hi) [1/σ(lo)] is modeled as an intergranular tunneling process with ρ(hi)=ρ(0)exp{C[(1−fc)/(1−f )]1/3−1}, ρ(0) and C being variable parameters. The log rms deviations for fits are W-Al2O3 (as prepared) 3.3%, W-Al2O3 (annealed) 0.66%, Ni-SiO (4.2 K) 2.3%, and Ni-SiO2 (291 K) 1.3%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347114
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  • 3
    Electronic Resource
    Electronic Resource
    A grain consolidation model for the critical or percolation volume fraction in conductor-insulator mixtures (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 3681-3682 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The critical volume fraction, at which the conducting component in conductor-insulator mixtures first becomes continuous or percolates, plays a very important role in both percolation theory and the generalized effective-media equation. The growth mechanism, by which very low (≤0.05) critical volume fractions for nearly spherical conducting powders in insulating hosts, such as polymers, are obtained, is not well understood. In this paper a simple model, based on the computer-generated model of Roberts and Schwartz [Phys. Rev. B 31, 5990 (1985)] for grain consolidation in porous media, for the very low critical volume fractions observed in some conductor-insulator mixtures is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.349216
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  • 4
    Electronic Resource
    Electronic Resource
    A tin whisker with two independent superconducting phase diagrams (1971)
    Springer
    Journal of low temperature physics 5 (1971), S. 665-681 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Whiskers grown by extrusion from tin plate are known to have irregular cross sections; one such whisker could be regarded as a cylinder of approximately 2 µ in diameter, attached to which, with its plane parallel to the cylinder axis, was a thin film of an approximate thickness of 1000 Å. The superconducting transition of this whisker was studied resistively as a function of magnetic field, temperature, and elastic strain, and is interpreted in terms of two independent phase diagrams, one being attributed to the cylinder and one to the thin film; size effects are discussed. It seems that the cylinder and the thin film behaved as two separate systems in parallel, allowing, for example, the coexistence of a stable superconducting state in the film and a metastable normal state in the cylinder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628416
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  • 5
    Electronic Resource
    Electronic Resource
    Ginzburg-Landau analysis of first-order transitions of elastically strained superconducting tin whiskers (1983)
    Springer
    Journal of low temperature physics 53 (1983), S. 375-404 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A recently developed Ginzburg-Landau-type equation has been used to analyze measurements of the effect of stress on first-order superconducting transitions of tin whiskers. Assumptions were made as to the temperature dependence of the effective penetration depth and the validity of simple similarity. The analysis is in terms of three parameters of bulk tin. The critical temperature was measured directly at each stress. The other two parameters, namely the zero-temperature values of the critical field and the effective penetration depth, were computed at each stress by an optimization procedure. Combination of the three parameters gives a reasonable estimate of the average Fermi velocity but cannot reveal if this is stress-dependent. The critical temperature is known to increase linearly with stress along the tetragonal axis and quadratically at right angles to it, and the critical magnetic field is found to increase similarly at a slightly higher rate. The results are compared with those obtained for the same whiskers in the second-order region, and also with other measurements of related properties, such as the change in length of bulk single crystals at the superconducting transition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00682485
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  • 6
    Electronic Resource
    Electronic Resource
    Quadratic response of the intermediate state to a transverse alternating magnetic field (1968)
    Springer
    The European physical journal 7 (1968), S. 226-231 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Description / Table of Contents: Résumé La réponse, ou susceptibilité, dans l'état intermédiaire d'un cylindre d'indium à un champ magnétique alternatif perpendiculaire à la fin au champ statique et à l'axe cylindre est étudiée en fonction de la fréquence, des dimensions, de la résistivité et de la température. La réponse est quadratique puisque un signal d'harmonique deux est engendré dans une bobine de détection parallèle au champ statique. A fréquences suffisamment basses la limite quasi-statique est atteinte. A fréquences intermédiaires le signal est amorti par Courants de Foucault, et à hautes fréquences le signal dépend de la structure de l'état intermédiaire.
    Abstract: Zusammenfassung Die Suszeptibilität des intermediären Zustandes eines transversalen Zylinders von Indium wurde mit Hilfe eines kleinen magnetischen Wechselfeldes (senkrecht zum statischen Magnetfeld und zur Zylinderachse) als Funktion der Frequenz, der Dimensionen, des Widerstandes und der Temperatur untersucht. Ein quadratisches Verhalten wird gefunden, da ein Signal doppelter Frequenz in einer Pickup-Spule axial zum statischen Magnetfeld erzeugt wird. Bei genügend niedriger Frequenz wird der quasistatische Grenzfall erreicht. Bei mittleren Frequenzen ist das Signal durch Wirbelströme gedämpft, und bei hohen Frequenzen hängt das Signal von der Struktur des intermediären Zustandes ab.
    Notes: Abstract The response or susceptibility of the intermediate state in a transverse cylinder of indium to a small alternating magnetic field perpendicular to both the static magnetic field and the axis of the cylinder is studied as a function of frequency, size, resistivity and temperature. The response is quadratic as a second harmonic signal is generated in a pickup coil axial to the static magnetic field. At sufficiently low frequencies the quasi-static limit is attained. At intermediate frequencies the signal is eddy-current damped, and at higher frequencies the signal is dependent on the structure of the intermediate state.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02422861
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  • 7
    Electronic Resource
    Electronic Resource
    First- and second-order superconducting phase transitions of tin whiskers in a magnetic field (1972)
    Springer
    Journal of low temperature physics 6 (1972), S. 385-395 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using a sensitive inductance technique, first- and second-order phase transitions in tin (type I) whiskers have been observed in both parallel and perpendicular magnetic fields. ForT much less thanT c the samples exhibit considerable superheating and supercooling from which values of the Ginzburg-Landau parameter κ are calculated. However, these values are not as low as those obtained for single spheres (diameters 10–30 µ), probably due to mean free path and size effects. Close to the transition temperature it is observed that the hysteresis vanishes indicating the onset of a second-order phase transition. Good qualitative agreement between these results and theoretical predictions based on the Ginzburg-Landau theory are obtained. Size effects on the ratioH C3/H C2 ≡H SC /H C2 are clearly illustrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00628319
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  • 8
    Electronic Resource
    Electronic Resource
    Quantum oscillations and reversible and irreversible superconducting phase transitions in indium microcylinders (1974)
    Springer
    Journal of low temperature physics 14 (1974), S. 607-626 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using a sensitive mutual inductance method, measurements of first- and second-order phase transitions in indium microcylinders (2.8–7.6 µm in diameter) have been made. Quantum oscillations in the supercooling field have been observed. The values of κ SC (T/T c )=κ1(T/T c ) derived fromH SC =H C3 have been corrected for both the temperature and the size dependence in the relationship betweenH c2 andH c3 . The results for κ1(T/T c ) from the 7.6-µm sample then agree reasonably well with the temperature dependence of κ1 observed for niobium. However, for the smallest cylinders anomalously low values of κ SC (T/T c ) were obtained nearT c . Very close to the transition temperature second-order (nonhysteretic) phase transitions have been observed and are interpreted in terms of the Ginzburg-Landau theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00658884
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  • 9
    Electronic Resource
    Electronic Resource
    The superconducting properties of PdHx≲1 (1977)
    Springer
    Journal of low temperature physics 26 (1977), S. 589-601 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Consecutive measurements of the magnetization curves and resistive transitions in magnetic fields have been made on PdH xT (x=H/Pd=0.9801−0.9957) foils between 2 and 10.4 K. The interpretation of the results is complicated by the fact that the magnetization curves are extremely irreversible and the hydrogen is distributed inhomogeneously in the samples. However, an analysis of the results shows PdH to probably be a type I superconductor with aT c of between 10.2 and 10.4 K, an HC(0) somewhat less than 900 G, and a κ of around 0.6 at absolute zero. Forx below about 0.995, PdH x becomes a type II superconductor due to the increasing resistivity of the material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655432
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  • 10
    Electronic Resource
    Electronic Resource
    Study of the volume fraction, temperature, and pressure dependence of the resistivity in a ceramic-polymer composite using a general effective media theory equation (1991)
    Springer
    Journal of materials science 26 (1991), S. 5899-5903 
    Details
    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 A quantitative general effective media (GEM) equation is used to describe quantitatively the resistivity of an Fe3O4-epoxy composite system over a large range of volume fractions in terms of the resistivities of each component and two percolation morphology parameters. One parameter is the critical (percolation) volume fraction, φc, and the other is an exponent,t. Preliminary models, also based on the GEM equation, are used to describe the positive temperature coefficient of resistivity (PTC) and the piezoresistivity (uniaxial pressure) of the composite when the composition is near the percolation threshold.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01130131
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