Flux Pinning in Y-Ba-Cu-O Superconductor Prepared by Melt-Powder-Melt-Growth Process

The YBaCuO prepared by the Melt-Powder-Melt-Growth (MPMG) process contains fine Y2BaCuO5 (211) inclusions embedded in the YBa2Cu3Ox matrix. Flux pinning force can be increased with increasing the volume fraction of the 211 inclusions. While MPMG processed Y1.5Ba2.25Cu3.25Ox which contains 25 volume % 211 inclusions exhibits a Jc value exceeding 3×104A/cm2 at 77K and 1T, YBa2Cu3Ox which contains no 211 exhibit a Jc value of 3×103A/cm2 at the same condition. Flux creep can also be reduced significantly by the 211 doping. These results support that the 211 inclusions can work as pinning centers. Theoretical estimation of flux pinning force due to the 211 inclusions was in good agreement with the experimental results. We also present the results of microstructural observation for MPMG processed YBaCuO with an emphasis on structural defects which can work as pinning centers.