Review of Chemical Solution Processes for Fabrication of Oxide Superconductors

Abstract

The situation of research and development of chemical solution routes to superconductors is reviewed, Chemical solution processes were compared with the processes using solid state-derived powders in terms of the processing factors affecting the critical current densities (Jc) of superconductors. Though powders derived by chemical solution methods have better characteristics than those derived by solid state processes, these improved characteristics have not been reflected in Jc, the level of which remains much too low for practical use. The low Jc value is due to high porosity and weak links at grain boundaries; this problem has not yet been solved. It is necessary to pursue two approaches in the development of chemical solution processes. One is to combine with processes that have already been developed to fabricate high Jc superconductors, applying the characteristics of chemical solution-derived powders (fine and uniform particles). Another is to fabricate high Jc superconductors by the solid state sintering method using ultra-fine and highly sinterable powders derived from chemical solution methods. The former is expected to be in practical use within several years and the latter will be necessary in long-range research and development.