Influence of Ho substitution of Y on flux pinning in melt-processed YBCO superconductors

Abstract

The Y1−xHoxBa2Cu3Oy (x=0, 0.2, 0.4 and 0.6) bulk samples were prepared by a ‘powder melting process' method. Their microstructure, critical current density and flux pinning behavior were investigated by TEM and SQUID magnetometer. The results indicate that Jc and flux pinning can be significantly improved by Ho substitution for Y. The normalized pinning force is found to be well scaled with the reduced magnetic field (h=H/Hirr) and shows a peak at hmax=0.4 in the Y0.4Ho0.6Ba2Cu3Oy sample, which is much higher than that in pure YBCO specimen. Many submicron binary RE211 particles and high density of stacking faults are observed in the Ho-doped samples, which may be responsible for the enhancement of Jc. Also, the paramagnetic moment of Ho has a large contribution to the increase in Jc.