CHINESE JOURNAL OF PHYSICS, cilt.47, ss.192-206, 2009 (SCI İndekslerine Giren Dergi)
The influence of the addition of the rare earth ion Gd in Bi1.8Pb0.35Sr1.9Ca2.1 Cu3GdxOy superconductor has been investigated by varying the Gd addition (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5). The samples were prepared by standard solid-state reaction methods. Phase analyses of the samples by X-ray diffraction (XRD), microstructure examination by scanning electron microscopy (SEM), superconducting properties by dc electrical resistivity, and mechanical properties by static Vickers hardness measurements have been carried out to assess the effects of Gd addition. These measurements indicated that the superconducting transition temperature, Vickers hardness, Young's modulus, yield strength, and fracture toughness values of the samples strongly depend on the Gd addition. The values of T-c, H-v, E, Y, and K-IC of the samples decreased with an increase in the Gd addition. Mechanical properties of the samples are also found to be load dependent. In addition, we have calculated the true (load independent) hardness, Young's modulus, yield strength, and fracture toughness of the samples. From XRD and SEM analyses, the addition to the sample of Gd degrades formation of the high-T-c Bi-2223 phase, the surface morphology, and the grain connectivity in comparison with an undoped sample. The possible reasons for the observed degradation in the superconducting and mechanical properties due to Gd addition were discussed.