The study of multiple thermal cycle of HTS YBCO bulk

The thermal cycle treatment has great influence on the superconducting property of the HTS (High Temperature Superconducting) YBCO bulk. The superconducting properties of the original and multiple thermal cycle treatment YBCO bulks are evaluated by VSM (Vibrating Sample Magnetometer) and the microstructures and the phase constituents of those are observed by SEM (Scanning Electron Microscope) and XRD (X-ray Diffraction). The result shows that JC (Critical Current Density) of the YBCO bulk deteriorates with the increase of the thermal cycle treatment times. And one or two times thermal cycle treatments do not harm the superconducting property of the YBCO greatly, however, after the third thermal cycle treatment, JC of the YBCO bulk drops to only 40% of the JC0 (original critical current density of the YBCO). Moreover, the microstructure analysis shows that c texture of the YBCO bulk remains unchanged during the three times thermal cycle treatments, and some decomposed phases (Cu rich phase) forming in the YBCO are the main reason for the superconducting property deterioration of YBCO bulk.