Abstract:
The influence of rare earth (RE – Ce, Gd) doping at the Nd site in the NdFeAsO0.7F0.3 superconductor
wherein Ce and Gd have ionic radii in the order Ce > Nd > Gd is investigated. The structural and
superconductivity characterization of the pure and doped samples show that Ce doping enhances the
TC of Nd1 xRExFeAsO0.7F0.3 to a maximum of 53.6 K at x ¼ 0.1 while Gd doping attains a TC of 55.1 K at
x ¼ 0.15. Interestingly, both Ce and Gd doping create neither secondary phases nor precipitates within
the detection limit of XRD. However, the lattice defects due to Ce and Gd doping modifies
NdFeAsO0.7F0.3 and assists in pinning the flux lines on these defects thereby exhibiting an enhanced
JC(H) performance especially at high fields. It is also observed that the relatively small ionic size of Gd is
more effective in TC enhancement, while the lattice defects due to larger ionic size of Ce favor the
remarkable enhancement of JC(H).
