Effect of Fe_2O_3 Nano-Oxide Addition on the Superconducting Properties of the (Bi,Pb)-2223 Phase

摘要

The effect of different weight percentages of nano-Fe_2O_3 on the properties of Bi_(1.8)Pb_(0.4)Sr_2Ca_2Cu_3O_(10+δ) superconducting phase was studied. Phase formation, elemental real contents and granular microstructure of the investigated samples were carried out using X-Ray powder Diffraction (XRD), Energy Dispersive X-ray emission (EDX), Proton Induced X-ray Emission (PIXE), Rutherford Backscattering Spectrometry (RBS) and Scanning Electron Microscopy (SEM). XRD data indicated that the volume fraction of (Bi,Pb)-2223 decreased as nano-Fe_2O_3 wt.% increased. PIXE and EDX analyses showed that the PIXE technique is more accurate for detecting the nano-Fe_2O_3 than the EDX technique. The oxygen content, determined from RBS, decreased as nano-Fe_2O_3 wt.% increased. The superconducting properties of the prepared samples were investigated using electrical resistivity and I-V curves, at 77 K, measurements. It was found that the granular structure and the critical current density were improved up to 0.2 wt.% of nano-Fe_2O_3 addition. The superconducting transition temperature T_c decreased as nano-Fe_2O_3 wt.% increased, attributing this to the decrease of the volume fraction or trapping of mobile holes. The enhancement rate of J_c for (Bi,Pb)-2223 phase added with nano-Fe_2O_3 is 9%, which is lower than that of (Bi,Pb)-2223 phase added with SnO_2, Ag_2O, Al_2O_3 and MgO. This means that the nanomagnetic addition has the lowest enhancement rate in both J_c and T_c.