Preparation of Fibers of Bi-Based Superconducting Ceramics

1.细棒、线圈：（1）用真空浇注法制备了Bi-Sr-Ca-Cu-0系的细棒和线圈等形状的陶瓷前驱体，并将其在800 ℃左右加热，得到了超导多晶陶瓷。确定了最佳的加热温度和加热时间，并讨论了试样加热过程中的吸氧量。用这种方法可以很容易地制备出长达50 cm的超导细棒（Tc 85 K）。(2)Up迄今为止，为了转化成超导陶瓷，已经在含氧气氛中加热前体铸态陶瓷。在本研究中，我们发现掺Ag_2 O熔体的铸态棒在真空密封容器中加热时，即在室温下加热时，可以转变为超导体。例如，在无氧气氛中。这一发现表明x，7 e能够制备出所需形状的玻璃封接的Bi基超导陶瓷.晶须：确定了2212相超导晶须的最佳制备条件，并从Al_2O_3添加剂的角度进行了讨论。

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.