Enhancement of critical current density and mechanical properties of BiPb-2223 superconductor phase added with Nano-sized Gd-123 phase

Ball milled Nano-sized of Gd-123 superconductor phase was added to the high temperature superconductor (HTSC) BiPb-2223 phase with weight percentage 2.0 wt.%. The milling times t was varied up to 180 min. The samples have a general stoichiometry of (Gd_1.0Ba_2.0Cu_3.0O_8+δ)_2.0/Bi_1.8Pb_0.4Sr_2.0Ca_2.0Cu_3.2O_10+δ. The samples were prepared by the standard solid-state reaction method. The ball milled superconductor Gd-123 phase was characterized by X-ray powder diffraction (XRD) and transmission electron microscope (TEM) confirming the Nano-scale crystallite size. The prepared samples were characterized by XRD and the scanning electron microscope (SEM). Samples were examined by electrical resistivity and IV measurements in addition to Vickers micro hardness. No significant change in the superconducting transition temperature T_c has been noticed for all samples. The highest relative volume fraction for BiPb-2223 phase was recorded for the sample with t = 120 min. The critical current density J_c was increased from 326, for free sample, up to 1860 A/cm², for added sample, with grain size 17.52 nm. The micro hardness data was analyzed using several models. The modified proportional sample resistance (MPSR) model is the model that can describe the behavior of our samples successfully.