Effect of Nd/Sr Partial Replacement on Characteristic Bi-2223 Phase and Related Fundamental Superconducting Parameters.

In the present work, the effect of Nd/Sr partial replacement on the crystallographic, morphological, electrical, and superconducting properties of Bi_1.8Pb₀.₃₅Sr_1.9-yNd_yCa_2.2Cu₃O_x materials is studied with the aid of powder X-ray diffraction (XRD), dc electrical resistivity versus temperature (ρ-T), scanning electron microscope (SEM), and electron dispersive X-ray (EDX) measurements. The crystal structure of new produced materials is defined in the tetragonal crystal system with the P_4/mmm space group. According to the experimental results observed, the quantity of characteristic Bi-2223 superconducting phase is found to reduce regularly with the enhancement of Nd nanoparticles in the crystal system, confirming that the replacement of Nd impurity at the Sr site causes an increase in the characteristic Bi-2212 superconducting phase. Similarly, the reductions of average crystallite size and c-lattice cell parameter as well as the systematic increment in the a-axis length verify that the partial Nd/Sr substitution deteriorates the Bi-2223 superconducting phase. Moreover, the experimental results display that the offset superconducting transition temperature ( T c offset ) is observed to decrease dramatically with increasing the concentration level of Nd impurity. In this context, the maximum T c offset parameter is noticed to be about 104.3 K for the pure Bi-2223 superconducting ceramic sample. This may be related to the degradation in the strength quality of transcrystalline regions, intergrain boundary couplings, and especially crystallinity quality. Furthermore, the SEM images demonstrate that the increment of Nd foreign impurities in the bulk Bi-2223 superconducting materials damages the flaky layers of platelet-like shape for the superconducting grains. [ABSTRACT FROM AUTHOR]