Ph.D. Tezi Görüntüleme

       In this study, Bi_(1.6)Pb_(0.4)Sr_2Ca_(2-x)Sm_xCu_3O_y samples were produced by solid state reaction method.

       The superconducting properties of the Bi_(1.6)Pb_(0.4)Sr_2Ca_(2-x)Sm_xCu_3O_y system have been investigated by x-ray diffraction (XRD), Diffrential Thermal Analysis (DTA), electrical resistivity (r-T), ac susceptibility, critical current density (J_c), thermal expansion coefficient, vickers hardness (Hv), scanning electron microskope (SEM) and optical microscope.

       X-ray diffraction (XRD) data showed that the volume fraction of the high-T_c (2223) phase decreased and the low-Tc (2212) phase increased as the amount of samarium content varied from x=0.0 to 0.01. At higher amount of samarium (x=0.1 to 1.5) there only exists the low-T_c phase. The thermal expansion coefficient decreased with the increase of Sm content. From the measurement of the vickers hardness, increasing the content of samarium in samples from x=0.0 to x=1.5 showed increasing value of hardness. SEM micrographs showed that the porosity in samples increased and inhomogenity appears with increasing Sm content.

       It was found that the critical transition temperature (T_c) decreased with increasing the amount of Sm_2O_3 in BSCCO system. Critical current density measurements were performed in liquid nitrogen temperature. Current densities of the samples were decreased by increasing amount of Sm concentrations from x=0.0 to 0.1. The critical current densities of the samples with higher Sm concentrations from x=0.5 to 1.5 can not be measured. Because, it was estimated that temperatures of samples were lower than liquid nitrogen temperature (77K).

       Keywords: Superconductors, doping of Sm_2O_3 thermal expansion coefficient, vickers hardness, transition temperature, critical current densities.

      not: _ = sub script