Investigation of effects of MgO nanoparticles addition on the superconducting properties of Bi-2223 superconductors

In this study, the effects of addition of magnesium oxide powders with average particle size <100 nm to Bi-2223 superconducting system were investigated. Bulk samples with general formula of Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O_y + (MgO)_x nominal composition (x = 0.00, 0.05, 0.10, 0.15 and 0.20 wt%) were prepared by conventional solid state reaction method. The critical temperature (T_c) and hole concentration (p) of nano MgO added samples were determined by AC susceptibility measurements. X-ray powder diffraction measurement (XRD) was used to examine phase formation, volume fraction and lattice parameters. The microstructure and surface morphology analyses of the samples were determined by scanning electron microscope. As Nano Mg addition was increased, surface morphology and grain connectivity of the samples were observed to degrade. XRD results showed that the lattice parameters do not change with increasing nano Mg addition. It was also observed from XRD measurements that volume fraction of Bi-2223 phase decreases with increasing nano Mg addition. The volume fraction of Bi-2223 phase for the non-added sample showed the highest value as 62.7% and further increasing nano MgO, the volume fraction of Bi-2223 phase decreases while Bi-2212 phase increases. The sample with 0.20 wt% MgO addition showed the highest volume fraction of Bi-2223 phase (~56%) and the highest superconducting transition temperature, T_c (~106 K) compared to added samples with nano MgO. The effect of nano Mg addition on magnetic properties of Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O_y superconductors were investigated by AC susceptibility measurements performed at ac fields of 1 Oe with f = 1000 Hz. The results revealed that critical temperature (T_c) decreases with increasing nano Mg addition down to 99.16 K.