Investigation of some physical properties of Gd added Bi-2223 superconductors

X-ray powder diffraction (XRD), scanning electron microscopy (SEM), dc electrical resistivity, critical current density and static microindentation measurements are performed to investigate some physical properties of Bi(1.8)Pb(0.35)Sr(1.9)Ca(2.1)Cu(3)Gd(x)O(y) superconducting samples with x = 0.0, 0.1, 0.3 and 0.5. We observe from the transport measurements that, for the Gd added sample, the critical transition temperature (T(c)) and the critical current density (J(c)) are decreased in comparison with that of undoped sample. In addition, surface morphology and grain connectivity of the samples are degraded and the high-T(c) phase of the samples decreases with increasing Gd addition. The indentation load versus diagonal length of the samples under different indentation loads in the range of 0.245-2.940 N are measured. The microindentation measurements showed that, for the Gd added sample, the load dependent (apparent) microhardness value (H(v)) is lower in comparison with that of the pure sample (x = 0). The values of H(v) are found to be load dependent. In addition, we extract the load independent (true) microhardness using the Kick's law, proportional specimen resistance (PSR), modified proportional specimen resistance (MPSR) and the Hays-Kendall (HK) approach and compare the true hardness with the apparent hardness. The possible reasons for the observed degradation in microstructure, superconducting and mechanical properties due to Gd addition are discussed. (C) 2010 Elsevier B.V. All rights reserved.