Effect of Oxygen Annealing on RE123 Superconducting Film Inferred From Changes in Microstructure

Coated conductors are actively manufactured by several wire companies around the worldwide to fabricate high-field magnets. The critical temperature of RE123 superconductors, used in these coated conductors, is significantly influenced by oxygen annealing during manufacturing. Recent observation of the microstructure in oxygen post-annealed and as-deposited films, fabricated via pulsed laser deposition, revealed significant differences in oxygen content and microstructural characteristics. Bayesian optimization was used to generate a two-dimensional map of annealing parameters for determining the optimal annealing temperature and duration in an oxygen atmosphere. This study presents the results of transmission electron microscopy observations of the microstructure in superconducting films deposited under various conditions identified on the map. The findings also infer the effect of oxygen annealing on microstructural changes.