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  • 1
    Electronic Resource
    Electronic Resource
    The superconductivity and metallurgy of C15 materials: Hf-V and Zr-V (1978)
    Springer
    Applied physics 17 (1978), S. 165-172 
    Details
    ISSN: 1432-0630
    Keywords: 74
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Variation of theT c as a function of composition for the C15 materials of the systems Hf−V and Zr−V was investigated. Samples in the as cast and annealed conditions were examined by x-ray and optical metallography. None of the samples was found to be of single phase. For the Hf−V system,T c increases to a constant value of about 9 K for the compositions between 36 and 60 at. %V. A slight increase ofT c between 60 and 70 at. %V and a degradation inT c above 80 at. %V were observed. As cast materials show the maximumT c value of 9.4 K. Deviations from stoichiometry and heat treatments produce considerable changes in the microstructures but have little effect onT c . A slight enhancement ofT c for the alloy containing 80 at. %V is explained by the pressure on V2Hf due to V phase by the differential thermal contraction. For the Zr−V system, maximumT c value of 8–6 K was observed for alloys having 20–66 at. %V in as cast condition. Heat treatments cause the lowering ofT c . Results indicate that the preparation of ZrV2 superconducting material will need more careful control than would be necessary for HfV2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00885250
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  • 2
    Electronic Resource
    Electronic Resource
    Comparison of superconducting and electronic properties of σ-and A-15 phase Nb−Al (1977)
    Springer
    Applied physics 13 (1977), S. 123-129 
    Details
    ISSN: 1432-0630
    Keywords: 74
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract For both, the σ-phase and the A-15 phase structure of Nb−Al binary alloys the superconducting properties were investigated in connection with measurements of normal state electronic properties like resistance and NMR-frequency and line width. The A-15 phase shows a transition temperature ofT c ≈17.5 K. The σ-phase shows only weak transitions at the same temperature which can be explained by A-15 inclusions in a non-superconducting σ-matrix. The Al27-Knight shift at room temperature is reduced from 0.162% for pure Al to (0.024±0.002)% and (0.026±0.0025)% for the A-15 and the σ-phase, respectively. The corresponding temperature coefficients differ in sign: positive for the A-15 and negative for the σ-phase; this may have a relation to the different superconducting properties. The NMR line width and the resistance show no different behaviour for the two phases. In general, the electronic properties seems to be less important for the occurance of superconductivity in the Nb−Al system than the lattice structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00882469
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  • 3
    Electronic Resource
    Electronic Resource
    Superconductivity of A15-and σ-phase of Nb-Ir (1979)
    Springer
    Applied physics 19 (1979), S. 231-235 
    Details
    ISSN: 1432-0630
    Keywords: 74
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The superconducting properties of A15-, σ-, and tetragonal phases of the system Nb−Ir were investigated. The alloys were prepared by sintering and arc melting. They were subjected to optical and scanning electron microscopy. The lattice parameters were determined by x-ray diffraction technique. Superconducting transition temperatures,T c , as well as upper critical fields,H c2, were measured inductively and resistively. TheT c -values of the σ-phase vary between 2.15 and 2.40 K whereas for the A15-phase they vary between 1.83 and 2.73 K. TheT c -value of the tetragonal phase is 3.81 K. The upper critical fields of the tetragonal and the A 15-phase are nearly the same (≈13 kG) and lower compared with that of the σ-phase (≈18 kG). Several theoretically predicted values ofH c2(0) are evaluated and compared with the experimental ones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00932403
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of superconducting parameters of A 15- and σ-phases of Nb−Pt (1978)
    Springer
    Applied physics 15 (1978), S. 307-313 
    Details
    ISSN: 1432-0630
    Keywords: 74
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The superconducting properties of A 15- and σ-phases of the system Nb−Pt were investigated. Alloys of compositions Nb3Pt, Nb2Pt, and Nb62Pt38 were prepared by arc melting and subjected to optical microscopic and x-ray analysis for structure determination. The transition temperatures were measured inductively as well as resistively. The temperature dependences of critical fields were measured up to 35 kG. The A 15-phase has aT c value of 8.97K and a zero temperature upper critical fieldH c2(0) of 100 kG as compared to aT c value of 2.14K and anH c2(0) value of 14kG for the σ-phase. A comparison with theoretical upper critical field values seems to indicate that a spin-orbit coupling mechanism is responsible for the higher value ofH c2(0) in the case of the A 15-phase alloy. The temperature dependent resistance up to 300 K is also measured and discussed for both the phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00896113
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