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Sökning: swepub > (1990-1994) > Sundqvist Bertil > Loberg Bengt

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1.
  • Andersson, Britt M., et al. (författare)
  • Electrical transport properties of dense bulk YBa2Cu4O8 produced by hot isostatic pressing
  • 1990
  • Ingår i: Physica. C, Superconductivity. - 0921-4534. ; 170:5-6, s. 521-531
  • Tidskriftsartikel (refereegranskat)abstract
    • Highly dense sintered YBa2Cu4O8 has been produced by hot isostatic pressing (HIP). The electrical resistivity varrho of this material has been measured as a function of temperature T and pressure varrho in the range 40–650 K and 0–0.7 GPa. Both the temperature dependence and the pressure dependence of varrho are found to be well described by a model based on the standard Bloch-Grüneisen theory. It is pointed out that varrho is liner in T only under isobaric conditions, while varrho is strongly nonlinear in all high-Tc superconductors under isochoric (constant volume) conditions. The critical current density of the material is 900 A/cm2 at 4 K, while the resistivity is 630 μΩ cm at 294 K.
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2.
  • Andersson, Britt M., et al. (författare)
  • Thermal conductivity of polycrystalline YBa2Cu4O8
  • 1994
  • Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121. ; 49:6, s. 4189-4198
  • Tidskriftsartikel (refereegranskat)abstract
    • We have measured the thermal conductivity κ and the thermal diffusivity a of a dense bulk ceramic polycrystalline sample of YBa2Cu4O8 (1:2:4) in the temperature range 30–300 K. We find κ≊10 W m-1 K-1 at 100 K, significantly higher than in ceramic YBa2Cu3O7-δ (1:2:3) and approaching the in-plane value for single-crystal 1:2:3, and decreasing to 7.6 W m-1 K-1 at 300 K. The data for this sample can be described by standard theories for phonon thermal conductivity of crystalline materials with boundary, phonon, and electron scattering. The higher κ in 1:2:4 as compared to 1:2:3 is, in this model, due to the smaller point defect scattering in the former. The fitted parameters for the three scattering mechanisms all agree with independent estimates based on simple models; inserting data for electric resistivity, grain size, carrier density, and lattice properties we can predict κ and its T dependence to within about 20%. We also discuss models for the phonon and electron thermal conductivities in some detail, including some second-order effects such as inelastic electron scattering and a T-dependent carrier density.
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3.
  • Niska, John, et al. (författare)
  • Formation of the 124 phase superconductor (YBa2Cu4O8) by retaining oxygen in a reaction HIP sintering process
  • 1990
  • Ingår i: Journal of materials science letters. - 0261-8028. ; 9:7, s. 770-771
  • Tidskriftsartikel (refereegranskat)abstract
    • The ceramic superconductor YBa2Cu4O8 has been produced by high temperature sintering of a mixture of CuO and YBa2Cu3O7 in a glass capsule under high hydrostatic argon pressure. The resulting highly dense material is investigated by X-ray diffraction, optical and electron microscopy, resistance measurements and hardness measurements, and shown to be a homogeneous High transition temperature superconductor.
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4.
  • Andersson, Britt M., et al. (författare)
  • Electrical transport in dense, bulk YBa2Cu4O8 produced by hot isostatic pressing
  • 1990
  • Ingår i: Physica B Volumes 165 & 166, Part 2 : LT-19 Part II: Contributed Papers, Proceedings of the 19th International Conference on Low Temperature Physics, Brighton 1990. - Elsevier B.V.. ; s. 1699-1700
  • Konferensbidrag (refereegranskat)abstract
    • Dense (98.5%) bulk sintered specimens of YBa2Cu4O8 have been produced by hot isostatic pressing. Data for the electrical resistivity π versus temperature T and pressure p in the range 70–300 K and 0–0.7 GPa are reported and discussed. The critical current density of the material studied exceeds 100 Acm−2 below 60 K.
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5.
  • Andersson, Britt M., et al. (författare)
  • High-pressure properties of high-Tc superconductor samples produced by hot isostatic pressing
  • 1990
  • Ingår i: High Pressure Research, volumes 3 to 5 : High Pressure Science and Technology: Proceedings of the 12. AIRAPT and 27. EHPRG Conference, University Paderborn 1989. - London : Gordon and Breach. - 2-88124-746-6 ; s. 123-126
  • Konferensbidrag (refereegranskat)abstract
    • The electrical resistance of dense YBa2Cu3Ox and YBa2Cu4Oy produced by hot isostatic pressing has been measured vs. T and p. At 295 K we find d (ln R)/dp ≃ -0.12 and -0.09 GPa-1, respectively, with no systematic dependence on initial density. For 1-2-4, dTC/dp ≃ 5.1 K/GPa, which is ten times that of 1-2-3.
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  • Resultat 1-5 av 5
Typ av publikation
tidskriftsartikel (3)
konferensbidrag (2)
Typ av innehåll
refereegranskat (5)
Författare/redaktör
Andersson, Britt M., (5)
Niska, John (5)
Easterling, Kenneth (3)
Easterling, Kenneth ... (1)
Lärosäte
Umeå universitet (5)
Luleå tekniska universitet (3)
Språk
Engelska (5)
Forskningsämne (UKÄ/SCB)
Naturvetenskap (5)
Teknik (1)

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