1998
DOI: 10.1088/0953-2048/11/10/003
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Optimization of processing to improve critical current density of Ag/Bi-2223 tapes

Abstract: Several recent developments in powder-in-tube (PIT) processing are presented. A cryogenic deformation process has been developed, involving rolling or pressing the wires and tapes in supercold conditions, such as in liquid nitrogen. Cryogenic deformation has been found to improve the density, grain alignment and Ag-oxide core interface and to increase dislocation density, thereby enhancing and flux pinning. By incorporating Pb into Bi-2212 phase the sintering temperature can be raised above , resulting in a s… Show more

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Cited by 12 publications
(5 citation statements)
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“…Bi-2223 phase purity, grain alignment and connectivity are important for control/optimization of the current transport properties of fully processed Ag/Bi-2223 composite wire because the critical current is transported by both intraand inter-granular mechanisms [3][4][5][6][7][8][9]. The intermediate deformation/size reduction following HT-1 is performed to remove the porosity created in the course of the HT-1 phase conversion process.…”
Section: Introductionmentioning
confidence: 99%
“…Bi-2223 phase purity, grain alignment and connectivity are important for control/optimization of the current transport properties of fully processed Ag/Bi-2223 composite wire because the critical current is transported by both intraand inter-granular mechanisms [3][4][5][6][7][8][9]. The intermediate deformation/size reduction following HT-1 is performed to remove the porosity created in the course of the HT-1 phase conversion process.…”
Section: Introductionmentioning
confidence: 99%
“…This technique ensures less mechanical deformation problems, such as sausaging and cracking, which severely restrict the J c . This advantage of oxide-layer coating may reveal a large potential to improve the J c , as these deficits are difficult to avoid in the widely used powder-in-tube (PIT) technique [17][18][19][20][21][22][23][24][25][26][27][28][29] due to its mechanically strong deformation characteristics. Two-step heat treatment has been developed for PIT-processed Bi-2223 tapes [25][26][27][28][29].…”
Section: Introductionmentioning
confidence: 99%
“…This advantage of oxide-layer coating may reveal a large potential to improve the J c , as these deficits are difficult to avoid in the widely used powder-in-tube (PIT) technique [17][18][19][20][21][22][23][24][25][26][27][28][29] due to its mechanically strong deformation characteristics. Two-step heat treatment has been developed for PIT-processed Bi-2223 tapes [25][26][27][28][29]. This process consists of two successive isotherms at different temperatures.…”
Section: Introductionmentioning
confidence: 99%
“…Long length 'green tapes' are produced by bundling these wires with ensuing hammerpressing, drawing and rolling of these bunches so that the ceramic powder is extended to filaments with ceramic cores of typically less than 20 µm thickness and a diameter of 60-200 µm. Conversion to the desired 2223 phase is obtained by a repeated heat treatment of these tapes, usually between 820 • C and 840 • C in atmospheres between 1% and 20% oxygen for various lengths of time [8][9][10][11]. This thermomechanical process must be controlled carefully to avoid sausaging and to improve grain connectivity.…”
Section: Introductionmentioning
confidence: 99%