Effect of rare-earth doping on the superconducting properties of MgB2.

The bulk polycrystalline samples with nominal compositions Mg1-x(Eu2O3)x/2B2 and Mg1-x(Pr6O11)x/6B2 (where x=0.0, 0.01, 0.02, 0.03, 0.04, and 0.05) have been prepared via standard solid-state reaction route. The x-ray diffraction (XRD) results of both series of materials reveal the presence of secondary phases MgO and REB6(RE=Eu/Pr) besides the main hexagonal phase of MgB2. The magnetic and electrical measurements show that transition temperatures (Tc) of both Eu2O3 and Pr6O11-doped MgB2 samples decrease from 39 to 37 K when values of x increase from 0.0 to 0.05. Improvement in critical current density (Jc) at 10 K has been observed at higher fields (>4 T) for Eu2O3-doped samples of composition x=0.04 and in entire field range (0–5 T) in the case of Pr6O11-doped samples of composition x=0.03 as compared to the Jc values of other compositions. The Jc values at 5 T field and 10 K of undoped, x=0.03 for Pr6O11-doped and x=0.04 for Eu2O3-doped MgB2 samples are 2.21×103, 1.15×104, and 1.10×104 A/cm2, respectively. Improvement in Hc2 and Hirr has also been observed in doped samples. [ABSTRACT FROM AUTHOR]