双粉法制备高性能Bi—2223／Ag多芯带材

HighQuality Bi2223/Ag Multifilament Tapes Fabricated Using a TwoPowder Process

摘要:

采用主相为２２１２＋ＣａＣｕＯ所谓双粉作为前驱粉，用标准的粉末套管（ＰＩＴ）工艺制备了３７芯，６１芯和８５芯ＢＩ－２２２３银包套多芯带材，研究发现，采用双粉装管缩短了２２２３成相时间，仅用４０ｈ即获２２２３纯相，前驱粉中较大尺寸２２１２片状晶的存在益于Ｃａ，Ｃｕ传质和２２２３织构的提高，通过对加工工艺的精确控制，可有效防止芯丝的不均匀，清除防碍长带制备的芯丝“香肠”状现象，首次实现了双粉法制备高性

Abstract:

Many studies have shown that the phase assemblage of starting powders influences the phase evolution of the 2223 phase; but it is quite difficult to control the phase balance in precursor powders using a singlepowder process. In this study, (Bi,Pb)2212 and CaCuO2 are formed as separate intermediate phases, then mixed and processed together within a silver sheath. The phase transformation kinetics, microstructure and transport properties of the resulting tapes are strongly dependence on the phase content of the precursor powders. Nearly pure 2223 can been produced when sintering for as little as 40 h, using (Bi, Pb)2212 and CaCuO2 presursors, and the fraction of nonsuperconducting phases seem to become minimum at the boundary of the oxide core. The effects of mechanical deformation and heat treatment cycles on silvercore interfaces and critical current densities in 37,61 and 85 filament tapes have been studied for the tapes fabricated using the twopowder process. A smooth Agoxide interface has been obtained through accurate control of the pass reduction ratios. This experiment demonstrates that the existence of large platelike 2212 grains in the presursors can accelerate the diffusion of Ca, Cu during sintering stage and increase the degree of texture of 2223 grains.Tapes with a thickness of 024 mm can be made using flat rolling without any sausaging effect. Jc values of 30104 A/cm2(Ic=53 A) and 17104 A/cm2(Ic=35 A) at 77 K and self field are achieved for rolled short samples and tapes 20 m long, respectively.