Silver-sheathed BiPbSrCaCuO wires were f a b r ic a t e d t h r o u g h t h e p o w d e r -i n -t u b e method. Jc-B p r o p e r t i e s , microstructures and Jc-strain properties wcre evaluated. Prototypes of coils and current leads were made and tested successfully.Critical current densities a t 77.3 K were 4 . 7~1 0~A/cm2 in a zero magnetic f i e l d , 3 . 1~1 0~ A/cm2 a t 0.1 'I'csla and 1 . 1~1 0~ A/cm2 a t 1 Tesla. In liquid He, 4.2 K, these wires can c a r r y 1 . 0 3~1 0~ A/cm2 a t 23 Tesla. J c and .Jc-B enhancements a r e due t o grain boundary improvements. Detailed investigation of Jc-B characteristics in magnetic fields, especially increasing and dccreasing f i e l d s , revealed t h a t h i s t o r y e f f e c t behaviors caused by weak l i n k s disappeared with improvements of grain boundary characteristics a t both temperatures. 1296 multifilamentary wires were shown t o sustain over 70 % of J c o even a f t e r a s t r a i n of up t o 0.GG % repeated 10 times. These r e s u l t s show f u t u r e possibilities of f l e x i b l e c a b l e s and r e a c t & windprocessed magnets. P r o t o t y p e s of c o i l s and c u r r e n t leads were fabricated using 20 m long wires. One c o i l showed critical currents of 54.2 A a t 77.3 K and 367 A a t 4.2 K. This coil generated B, of 142 Gauss a t 77.3 K and 87G Gauss a t 4.2 K. Critical c u r r e n t p r o p e r t i e s were investigated with back-up fields of up t o 990 Gauss a t 77.3 K and 3.7 Tesla a t 4.2 K. A prototype of react & wind-processed coil was demonstrated using o v e r 4 m I o 11 g mu 1 t i f i 1 am e n t a r y w i r e s , a n d s u c c e s s f u 1 l y produced enough magnetic f i e l d t o r o t a t e c o p p e r windings between s t e e l cores. 50 cm long c u r r e n t leads were made and t e s t e d a t 77.3 K and proved t o carry 242 A, showing overall current d e n s i t y of 2000 A/cm2 including silver-sheath.
Critical current density (J
c) and its dependence on magnetic field in Ag-sheathed Bi-Pb-Sr-Ca-Cu-O superconducting wire was improved by grain alignment and homogenization of the high-T
c phase (110 K). The maximum transport current density at 77.3 K in a zero magnetic field was increased to 6930 A/cm2. The magnetic field dependence of J
c (0.1 µV/cm criterion) was summarized as follows: 1660 A/cm2 (I ⊥H, a-b plane ∥H, 0.1 T), 900 A/cm2 (I ⊥H, a-b plane ⊥H, 0.1 T). We found that the grain boundaries were bonded strongly in the direction of alignment.
Critical currents of superconducting silver-sheathed tapes of Bi1.8Pb0.4Sr2Ca2.2Cu3Ox have been measured in the magnetic flux density range 0–19.75 T at 4.2, 15, and 20 K. One tape achieved a critical current of 60.6 A at 19.75 T and 20 K; the corresponding critical current density is 551 A/mm2. In the same field, the tape has critical currents of 72.3 A (657 A/mm2) at 15 K and 94.2 A (856 A/mm2) at 4.2 K. At 77 K and in zero field, the tape carries 32.9 A (299 A/mm2). These results indicate that ‘‘high Tc’’ superconducting magnets of engineering interest may soon be feasible.
We prepared silver-sheathed BiPbSrCaCuO wires by the powder-in-tube method. Maximum critical current densities at 77.3 K were 5.4×104 A·cm-2 in a zero magnetic field, 4.2×104 A·cm-2 at 0.1 T and 1.2×104 A·cm-2 at 1 T. At 77.3 K, as the J
c improves, the history effects decrease. J
c and J
c-B enhancements are due to the decrease and dispersion of nonsuperconducting phases, and to grain boundary improvements.
We report a detailed study of the temperature and magnetic-field dependence of free energy, magnetization, and specific heat of superconducting Bi2Sr2Ca2Cu30&0 in the critical fluctuation region near H, 2(T) line. Our approach is to apply the recently developed nonperturbative scaling theory (Tesanovic et al. ) in high fields to describe the reversible magnetization data taken on a c-axis-oriented superconducting Bi2Sr2Ca2Cu30&0 thin tape. We find good agreement on some of the superconducting parameters obtained in the present study with those derived by applying the Ginzburg-Landau theory to our reversible magnetization data taken outside the critical fluctuation region.
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