The effect of Ni–Zn ferrite doping on the superconductivity of Y3Ba5Cu8O18 nanocomposite materials

Nanocomposite materials of the Y3Ba5Cu8O18/(Ni0.5Zn0.5Fe2O4)x type, where x = 0.00 wt. %, 0.03 wt. %, 0.10 wt. %, and 0.50 wt. %, are synthesized by the improvement of the solid-state reaction technique. The prepared samples have been characterized by x-ray diffraction (XRD), scanning electron microscopy, x-ray energy dispersion, infra-red spectroscopy, thermo-gravimetric analysis, four probe DC resistance, and current–voltage (I–V) measurements. It was found that the prepared samples have an orthorhombic structure with unit cell parameters (a = 3.9557 Å, b = 3.8197 Å, and c = 30.2460 Å) for pure Y358, and the unit cell volume decreases by the addition of (Ni0.5Zn0.5Fe2O4) nanoparticles into the Y358 compound. The crystallite size (D) was evaluated from XRD patterns by Scherrer’s method. The crystallite size (D) is decreased from 40 nm for pure Y358 to 18 nm for Y358 doped by the Ni–Zn nanoferrite content of 0.50 wt. %. The critical current density Jc and I–V characteristics for superconductor/nanoferrite (Y358/Ni–Zn) composite materials are explained according to Bean’s critical state model and the charge–vortex duality in the Y358 high-Tc mixed-state.