Title :
The influence of long reaction time on various properties of monocore Bi-2223/Ag tapes
Author :
Marti, F. ; Dhalle, M. ; Flukiger, R. ; Grasso, G. ; Grivel, J.-C.
Author_Institution :
Dept. de Phys. de la Matiere Condensee, Geneva Univ., Switzerland
fDate :
6/1/1999 12:00:00 AM
Abstract :
The mechanisms leading to a maximum of j/sub c/ as a function of reaction time in (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ monofilamentary tapes are investigated. Various properties of tapes previously reacted 40 hours in air at 837/spl deg/C, rolled, and submitted to additional reaction during times varying from 40 to 240 hours were measured. The evolution of morphology, phase assembly, stoichiometry, weight, critical temperature, critical current and irreversibility line is described. XRD and SEM analysis reveal no decomposition of the Bi(2223) phase and no noticeable grain growth in the time window under investigation. Pb losses as function of reaction time up to 40% were detected by means of thermogravimetry and EDX, while an increase of T/sub c/ from 107.25 to 109.1 K was observed. Transport and magnetic measurements show that the observed maximum of j/sub c/ at about 180 hours is the result of two competing effects: a) an improvement of the quality of grain boundaries and b) a decrease of the pinning efficiency in the grains.
Keywords :
X-ray chemical analysis; X-ray diffraction; bismuth compounds; calcium compounds; critical current density (superconductivity); crystal morphology; density; flux pinning; grain boundaries; high-temperature superconductors; lead compounds; magnetisation; phase equilibrium; scanning electron microscopy; silver; stoichiometry; strontium compounds; superconducting tapes; superconducting transition temperature; thermal analysis; (BiPb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O-Ag; (BiPb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ monofilamentary tapes; 107.25 to 109.1 K; 40 h; 40 to 240 h; 837 C; EDX; Pb losses; SEM; T/sub c/; XRD; critical current; critical temperature; grain boundaries; irreversibility line; j/sub c/; long reaction time; magnetic measurements; monocore Bi-2223/Ag tapes; morphology; phase assembly; pinning efficiency; stoichiometry; thermogravimetry; transport measurements; weight; Annealing; Critical current; Grain boundaries; Heat treatment; Magnetic field measurement; Magnetic variables measurement; Physics; Powders; Solid state circuits; Temperature;
Journal_Title :
Applied Superconductivity, IEEE Transactions on
