Effects of Gd substitution on magnetic, structural and superconducting properties of Bi_1.7−xPb_0.3Gd_xSr₂Ca₂Cu₃O_y

The effects of Gd addition on the structural and magnetic properties of Bi_1.7−xPb_0.3Gd_xSr₂Ca₂Cu₃O_y (x = 0.00–0.20) superconducting samples were investigated. The samples were prepared by conventional solid state reaction method. The phase formation, phase fraction and lattice parameters were determined from X-ray diffraction (XRD) measurements, while the microstructure, surface morphology analyses of the samples were carried out using scanning electron microscope. As Gd addition was increased, surface morphology and grain connectivity of the samples were observed to degrade. XRD results indicated that the lattice parameter c decrease with increasing Gd addition while Bi-2223 phase disappear and Bi-2212 phase become dominant. AC susceptibility measurements were performed at various ac fields (ranging from 20 to 160 A/m) to understand the effect of Gd addition on magnetic properties of Bi_1.7−xPb_0.3Gd_xSr₂Ca₂Cu₃O_y superconductors. The results showed that both critical temperature (T_c) and critical current densities (J_c) were found to decrease with increasing Gd addition. It was found that T_c values decrease from 108 to 70 K with increasing Gd addition.