| 1. |
- Diederichs, J., et al.
(författare)
-
Critical currents in Tl-2122 and Y-124 sinters under high hydrostatic pressure
- 1991
-
Ingår i: Superconductor Science and Technology, volume 4, Special Issue 1S. - Bristol : Adam Hilger. - 0750301082 ; , s. S97-S99
-
Konferensbidrag (refereegranskat)abstract
- Utilizing AC susceptibility measurements the authors have investigated the inter and intragranular properties of selected bulk materials under hydrostatic pressures to 3.5 GPa. A single phase Tl2CaBa2Cu2O8 sample with superconducting transition temperature Tc approximately=107 K shows a clear maximum in Tc(P) at approximately 2.2 GPa coupled with a nearly twofold increase to 3 GPa of the intergranular critical current density JcJ near Tc. The second sample, a YBa2Cu4O8 sinter, shows a large linear increase in Tc with pressure (+5.5 K/GPa) as well as a fivefold increase JcJ to 3 GPa. Applying a critical state model, the authors find that Tc(P) varies as lambda g-2(P), where lambda g is the intragranular (London) penetration depth.
|
|
| 2. |
- Staun Olsen, J., et al.
(författare)
-
High pressure studies up to 50 GPa of Bi-based high-Tc superconductors
- 1991
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 44:2, s. 211-213
-
Tidskriftsartikel (refereegranskat)abstract
- The high-Tc superconductor with nominal composition BiSrCaCu2Ox has been studied at high pressure, i.e. up to 50 GPa. A tetragonal structure was compatible with the measurements at all pressures, and no phase change was observed. The bulk modulus, B0 = 62.5 GPa, obtained has a somewhat smaller value than the one estimated earlier.
|
|
| 3. |
|
|
| 4. |
- Sundqvist, Bertil
(författare)
-
The electrical resistivity of La under pressure between 70 and 300 K
- 1991
-
Ingår i: High Pressure Research, volume 7 and volume 8, issues 1-3. - Reading : Gordon and Breach. ; , s. 250-252
-
Konferensbidrag (refereegranskat)abstract
- The electrical resistivity of fcc La has been measured as a function of temperature and pressure between 70 and 300 K. The pressure coefficient of resistance dlnR/dp is found to decrease from +0. 022 GPa-1 at 75 K to -0. 014 GPa-1 at 300 K.
|
|
| 5. |
- Sundqvist, Bertil
(författare)
-
Thermal diffusivity measurements by Ångström's method in a fluid environment
- 1991
-
Ingår i: International journal of thermophysics. - 0195-928X .- 1572-9567. ; 12:1, s. 191-206
-
Tidskriftsartikel (refereegranskat)abstract
- Ångström's method has been used for measuring the thermal diffusivity, a, and the radial heat loss coefficients of a thin constantan wire, both in a vacuum and with the wire immersed in air and in four different liquids, and using temperature wave periods of 1 to 1000 s. The presence of a surrounding fluid medium causes errors of up to 90% in the measured values of a. It is shown that both the experimental errors and the radial heat loss coefficients can be accurately calculated using simple models, both at high and at low frequencies, and that a previously developed two-frequency model can be used to obtain accurate data for a even under these conditions, provided the frequency is high enough. We also present a new variety of Ångström's model, valid only at very low frequencies and with purely convective heat loss.
|
|
