The Role of Oxygen in the Hot Isostatic Pressing of High Tc Superconductors

Abstract

ABSTRACTThe bismuth-based 2212 and 2223 superconductors and the yttrium-based 123 and 124 high Tc superconductors are oxide ceramics, so that oxidizing conditions must be maintained in the HIP to avoid oxygen loss and decomposition. This has been done in an argon gas HIP by using glass encapsulation, but internal gas pressure retards densification. The thermodynamics of the release of oxygen by the superconductive ceramics and the stability of the metal to oxygen can be shown on a free energy diagram (Ellingham diagram). The base metals (as Fe and Cu) are reactive with respect to superconductive ceramics but not silver.