Addition effects of nanoscale NiO on microstructure and superconducting properties of MgB2

We have investigated the addition effect of NiO magnetic nanoparticles on crystal structure, microstructure as well as superconducting properties of MgB2. NiO-added MgB2 samples were prepared by the solid-state reaction method. The superconducting transition temperature (T-c) of 37.91 K was obtained for pure MgB2, and T-c was found to decrease systematically on increasing the addition level of NiO. X-ray diffraction (XRD) analysis revealed that no substitution of Ni for Mg in the lattice of MgB2 was occurred. The microstructural analysis shows that the pure MgB2 sample consists of plate shape MgB2 grains, and the grains get refined to smaller size with the addition of NiO nanoparticles. At 5 K, high values of critical current density (J(c)) were obtained for small amount NiO-added MgB2 samples as compared to pure sample. The enhancement in J(c) could be attributed to the refinement of MgB2 grains which leads to high density of grain boundaries in NiO-added MgB2 samples.