Effect of Rare-Earth Oxides Doping on the Superconductivity and Flux Pinning of MgB2 Superconductor

A series of rare-earth-oxide-doped MgB2 bulks are prepared by in situ solid-state reaction with Pr6O11, CeO2, Lu2O3, and Ho2O3 as the dopants. The superconducting properties are investigated and compared with the nano-Fe3O4 doped MgB2. It is found that different from doping ferromagnetic nano-Fe3O4 which drastically suppresses superconductivity of MgB2, doping the rare-earth-oxides has little effect on superconductivity of MgB2 although most rare-earth elements have strong magnetic moment. In addition, some boride impurities formed during the reaction between rare-earth oxides and boron can work as effective pinning centers and significantly improve J (c) and H (irr) of MgB2 when these fine nanoboride precipitates (< 20 nm) are embedded into the MgB2 intragrains.