Study of Improved Critical Currents and Mechanical Properties in the Y-Ba-Cu-OSuperconductor with Silver or Y2BaCuO3 or 211 Dispersions

摘要

The microstructure of the top-seeded, single grain, melted textured YBCOmaterials with different vol% 211 were investigated. The homogeneity of 211 distribution was greatly improved by using a solution precipitated 211 powder in preparation. Crack spacings and twin spacings were found to decrease with increasing vol% of the 211 particles. The 211 particles were found to be effective in holding crack propagation. Relationship between twin spacing and interparticle spacing was found to depend on the elastic strain energy from the tetragonal to orthorhombic transformation. The accumulative beneficial effects of the 211 addition on Jc are summarized. The highest Jc was 10(exp 4) A/sq cm at 77K 1T. Our transmission electron microscopy of the Au/YBCO interfaces shows well-bonded interfaces with no extraneous phases present with the (001) lattice fringe of YBCO terminated at the interfaces abruptly. Both integral steps of (001) height and multiples of 1/3(001) steps were observed. Our finding supports earlier contact resistivity and XPS results of the Au/YBCO interfaces. Amorphous carbon films were shown to protect superconducting YBCO films from degradation by humidity. The YBCO films with carbon coating were founded to retain critical current densities 4 orders of magnitude higher than the uncoated YBCO films after 2h at 100% relative humidity stressing at room temperature.