(Bi,Pb)_2Sr_2Ca_2Cu_3O_x超导带材的微结构研究

MICROSTRUCTURAL INVESTIGATION OF Ag-SHEATHED (Bi,Pb) 2Sr 2Ca 2Cu 3O x SUPERCONDUCTING TAPES

对Ｂｉ系带材内部的微观组织进行了详细研究．发现带材横截面内各部位的织构度和显微硬度存在差异，从银层和氧化物接触面处到粉芯中心，织构度依次减弱，而显微硬度逐渐增加．中心区组织凌乱，存在着许多大而硬的杂质第二相．织构度梯度的存在表明带材截面内各部位晶粒的取向差异；减少非超导相，有助于获得高Ｊｃ．分析表明，轧制和冷压过程中的应力不均匀造成了带材内部变形的不均匀，这一切就导致了带材内部组织结构的不均匀．因此为获得内部组织结构均匀的带材。

The relation between microstructure and J c of the tapes was investigated by means of XRD, SEM and Vickers hardness.It is found that there are variations of the density and the degree of texturing within the core of the tape.The degree of texturing decreases from the Ag/2223 interface towards the center of the oxide core.This demonstrates that there exist non_uniform characteristics in the tapes made by the present technology.Firstly this is perhaps due to uneven stress and deformation distribution during rolling and cold pressing as well as inhomogeneity within ceramic itself.Secondly, it is also due to the very different grain structure between the edge and central region in the tapes.It is shown that uneven stress distribution leads to non_uniform microstructure in the tapes, thus it is necessary to develop a new fabrication technology to obtain tapes with uniform microstructure.