Preparation of Fibers of Bi-Based Superconducting Ceramics

1. (1)在Bi-Sr-Ca-Cu-0体系中，通过真空铸造熔体，成功制备了给定形状的前驱体陶瓷（如直径mm的细棒）和线圈；玻璃状前驱体，铸态样品，在800℃左右再加热后转化为超导多晶陶瓷。确定了加热温度和持续时间的最佳加热条件，并从试样加热过程中吸氧的角度进行了讨论。该工艺可制备长度达50 cm的超导细棒（Tc 85K）。(2)迄今为止，为了将铸态前驱体转化为超导陶瓷，都是在含氧气氛中加热。在这项研究中，我们发现掺ag20熔体的铸态棒在真空密封容器中加热时，即在无氧气氛中转化为超导体。这一发现表明，x， 7e能够制造出理想形状的密封在玻璃中的超导铋基陶瓷。晶须：以Al_2O_3为添加剂，确定并讨论了2212相超导晶须的最佳制备条件。

1. Fine rods, Coils :(1)A given shape of precursor ceramics such as fine rods mm diameter)and coils in the system of Bi-Sr-Ca-Cu-0 was successfully fabricated by a vacuum casting of the melts into a given shape of silica glass tube ; the glassy precursors, as-cast specimens, were converted into superconducting polycrystalline ceramics by reheating them at around 800'C. The optimum heating conditions for heating temperature and-duration time were determined, and discussed in terms of oxygen absorption during heating of the specimen. Superconducting fine rods(Tc 85K)up to 50 cm length were easily prepared by this process.(2)Up to date, the precursor as-cast ceramics have been heated in oxygen-containing atmosphere in order for the conversion into superconducting ceramics. In this study, we found that the as-cast rods of Ag2O-doped melts are converted into superconductor when heated in a vacuum sealed-vessel, i. e., in oxygen-free atmosphere. This finding indicates x, 7e are able to fabricate a desired shape of superconducting Bi-based ceramics sealed in glasses.2. Whiskers : Optimum preparation conditions of superconducting whiskers (2212 phase) were determined and discussed in terms of Al_2O_3 additives.