Relationship between critical current properties and microstructure of Er123 melt-solidified bulks

We report impurities doping effectors of Pt and/or CeO/sub 2/ of microstructures, critical temperatures and critical current density (J/sub c/) in both a-growth and c-growth regions of the ErBa/sub 2/Cu/sub 3/O/sub y/ (Er123) melt-solidified bulks. The volume fraction of the Er/sub 2/BaCuO/sub 5/ (Er211) particles in Er123 matrix was always lower in the c-growth region than in the a-growth region. However, the second peaks of J/sub c/-B curves were more prominent in the c-growth region and its maximum J/sub c/ value reached 53 kA/cm/sup 2/ at 77 K under a magnetic field of 1 T for the bulk of the co-doping of 0.5 wt% Pt and 1.0 wt% CeO/sub 2/. Whereas the Er211 particles were finely dispersed in Er123 matrix in each case of Pt- or CeO/sub 2/-addition, the co-doping of Pr and CeO/sub 2/ showed most refined effect of the dispersion of Er211 particles. From the results of microstructures and J/sub c/, J/sub c/ value at zero field was found to be systematically improved with the reduction of diameter of the Er211 particles.