Fabrication of bismuth(2) strontium(2) calcium copper(2) oxygen(8) superconductors from flux grown crystals.

摘要

The fabrication of multilayered Bi-2212 ceramics by using a combination of simple processing techniques such as molten salt powder synthesis and tape casting by a doctor blade method was achieved.;Molten salt synthesis is a viable way to obtain platy Bi-2212 crystallites. The systems identified as the best, economically and for their ability in promoting anisotropic Bi-2212 crystallite growth are KCl, KCl-RbCl and KCl-CsCl salts. It is postulated that Na is substituting on the Ca site, poisoning the superconductor. It is also postulated that bigger ions poison the growth of crystallites in the c-direction resulting in thinner and better flakes. This means that ;Multilayered oriented ceramics are fabricated by tape casting, utilizing the anisotropic Bi-2212 crystallites synthesized by molten salt synthesis. The maximum density of these ceramics was 90% of the theoretical, and no improvement was achieved using liquid phase additions. Annealing or processing in a reducing atmosphere increased the transition temperature (T;Hot forging (i.e., application of pressure during sintering) and addition of silver helped in improving the grain-to-grain connectivity but not the density of the ceramics. The maximum critical current density (J