Doping of Nb to the Ba and Cu Sites in the Y0.6Gd0.4Ba2Cu3O7-δ

Polycrystalline samples of Y0.6Gd0.4Ba2-x Nb (x) Cu3O7-delta and Y0.6Gd0.4Ba2Cu3-x Nb (x) O7-delta with different Nb contents (x=0.025, 0.075, 0.125, 0.175 and 0.225) were prepared using the solid state reaction method. Structural and electrical properties of new compounds were investigated with optical microscope, scanning electron microscopy (SEM), X-ray diffraction (XRD), Four Point Probe (FPP). The results indicated that Nb constituted YBa2NbO6 structure instead of substituting to the Y0.6Gd0.4Ba2Cu3O7-delta structure. YBa2NbO6 structures gathered between grains. Transition temperature did not change significantly, but critical current (J (c)) values decreased with increase of Nb concentration. The underlying reason is that the oxygen concentration of compounds remained unchanged due to Gd; thus, T (c) values did not change significantly.