Phase Equilibrium in Multicomponent System and Material Design of Bi-based Suprconductors

为了研究Bi-Pb- sr - ca - cu - o的相图，我们设计了一种独特的防止挥发性元素Bi和Pb损失的电池，该电池由银制成的容器和盖组成。结果表明，在750 ~ 850℃温度范围内，氧通过银层向外扩散，而其他阳离子不丢失。主要研究了Bi2212和Bi2223的相关系。首先阐明了恒压条件下的不变反应。利用有关相关系的实验数据，利用计算机软件thermal - calc建立了多组分体系的相图。具有高临界电流密度的样品由4 ~ 6相的多相组成。通过对材料成分和温度的精确控制，使Bi2223相的体积分数达到90-95%，临界电流密度达到最大，力学性能得到很大提高。

In order to investigate the phase diagram of Bi-Pb-Sr-Ca-Cu-O, we designed an unique cell preventing the loss of volatile elements, Bi and Pb, which is consisted of container and lid made from silver. It was confirmed that oxygen diffuses out through the silver layer, but other cations do not lose in the temperature range between 750 and 850 ℃. Mainly the phase relations relating to Bi2212 an Bi2223 have been investigated. Firstly the invariant reaction was made clear under constant pressure. By using the experimental data with respect to the phase relations, the phase diagram of multi-component system has been established by means of the computer soft "Thermo-Calc".The samples exhibiting high critical current density consist of multi-phases with 4 to 6 phases.When the precise control of composition and temperature was carried out, the volume fraction of Bi2223 phase was achieved to 90-95% while the critical current density was maximized and the mechanical property was greatly improved.