Optimization on processing parameters for Bi(Pb)-2223 superconducting tapes

The powder-in-tube technique is the most widely used method for fabricating silver-clad Bi-2223 wires and tapes. In this method the silver billet containing the precursor material is transformed to the final shape using metallurgical deformation techniques such as wire drawing and flat rolling. In the present study, a modified version of the powder-in-tube technique was adopted where the silver billet was reduced in size by groove rolling instead of wire drawing. Microstructural analysis during the initial deformation stage revealed crack formation in the superconductor core. Stress conditions during groove rolling were analysed and appropriate changes were incorporated in the deformation process. After groove rolling the wires were flat rolled to a final thickness of 250 m. Subsequent thermomechanical treatment resulted in tapes with critical current density of 19700 A cm-2 (critical current of 40 A).

Section: Introductionmentioning

confidence: 99%

Phase development and critical current density of Bi-2223 tapes fabricated by groove rolling

Iyer

Salib

Vipulanandan

et al. 1999

“…Furthermore, one of the keys to prepare samples which exhibit high critical current densities (J c ) is to control the grain size. Many groups reported that with the PIT process, a small grain size is favourable to obtain a high J c [11][12][13][14]. A fine precursor powder increases the reactivity, which under appropriate conditions promotes the Bi2223 phase formation and increases the intergrain connectivity.…”

Section: Introductionmentioning

confidence: 99%

Sinter-forging of strongly textured Bi2223 discs with largeJ_cs: nucleation and growth of Bi2223 from Bi2212 crystallites

Guilmeau

Chateigner

Noudem

2002

Dense Bi2223 superconductor discs with a highly oriented structure were prepared by the sinter-forging method. A detailed investigation of the processing parameters has been carried out on the phase assemblage, the particle size of the calcined precursor powder and the sinter-forging time and temperature. A high transport critical current density, J c , was obtained from a starting powder rich in Bi2212 and secondary phases. Using fine powder, a high degree of orientation, larger than those of multifilamentary tapes, and excellent intergrain connection were observed. The optimal sinter-forging temperature was found to be in the range of 845-850• C and the transport critical current densities reached values of 12 700 A cm −2 at 77 K in self-field. The combination of textural and microstructural investigations testify that a nucleation-growth mechanism from the Bi2212 particles is responsible for the Bi2223 phase formation, rather than an intercalation process.

“…As a preceding step of the PIT process, the precursor powder was proven to be of vital importance to the phase formation, microstructure evolution and J c properties. Some parameters related to the precursors, such as calcination temperature [4][5][6][7][8][9][10], particle size distributions [11][12][13][14], lead variations [15,16], and carbon content [17], have been studied to improve the J c performance of Bi-2223/Ag tapes. Among these aspects, the calcination temperature and particle size of the precursor powders are two very sensitive factors for the phase formation and transport J c .…”

Section: Introductionmentioning

confidence: 99%

“…The fine and homogeneously distributed particles in precursors have been generally recognized as the best choice for getting faster phase formation, larger grain size, better grain alignment and higher J c values [11][12][13][14]. But too fine particles also induce large secondary phases, which preferably locate at the grain boundaries and thus destroy the connectivity of the 2223 grains and degrade the transport property and flux pinning ability [11].…”

Section: Introductionmentioning

confidence: 99%

Optimization of precursor powders for manufacturing Bi-2223/Ag tapes

Jiang

Yoo

et al. 2002

The phase assemblage and particle sizes of precursor powders have been optimized in a sequence for fabricating Ag/BSCCO-2223 composite tapes. Firstly, an optimal calcination temperature was determined based on the experimental results. Then, the precursors calcined at the optimal temperature were ball-milled for different dwell times to obtain varied particle sizes. The effects of both the phase assemblages and particle sizes of the precursor powder on the phase formation, microstructure and transport J c of Bi-2223/Ag tapes have been investigated. The results show that the precursor phase assemblage has a large impact on the reaction routes, microstructure, and J c property. Meanwhile, a fine powder is beneficial for the grain growth, alignment, and J c enhancement in fully reacted tapes. The best J c was achieved in the tape made from the powder after optimizing the phase assemblage and particle size.