The study of multiple thermal cycle of HTS YBCO bulk

► The thermal cycle treatment has great influence on the superconducting property of the HTS YBCO bulk. ► JC (Critical Current Density) of the YBCO bulk deteriorates with the increase of the thermal cycle treatment times. ► JC of the YBCO bulk drops to only 40% of the JC0 after three times thermal cycle process. ► Some decomposed phases (Cu rich phase) are the main reason for the superconducting property deterioration of YBCO bulk.