Effects of Yb-doping on flux pinning properties in YBa2Cu3O7-δ

The effects of Yb-doping on the critical current density (Jc) and the critical temperature (Tc) in YBa2Cu3O7-δ (YBCO) were investigated. Rietveld refinements of X-ray diffraction showed that Yb3+ ions had partly substituted Y sites in YBCO and the unit cell volume V decreased monotonically as x increasing. Although Tc almost had no change with increasing Yb-concentration, the increase of Jc occurred as a field was applied and displayed a maximum at x=0.08. We argued that the formation of nanometric inhomogeneity may lead to the enhancement of pinning force.