Evolution of electrical, superconducting, crystallinity and structural features with aliovalent Nd/Sr replacement in Bi-2223 ceramics

This paper blazes the trail for the understanding of fundamental characteristic features for Bi-2223 ceramic with aliovalent Nd/Sr replacement in Bi1.8Pb0.35Sr1.9-yNdyCa2.2Cu3Ox superconducting matrix (0.00 < y < 0.10). Full characterization of superconductors is performed by conventional experimental methods, viz. X-ray diffraction (XRD), dc electrical resistivity based on temperature (rho-T), electron dispersive X-ray (EDX) and scanning electron microscopy (SEM) examinations. Measurement results display that the trivalent Nd+3 ions may partially be substituted by Sr+2 impurities in the Bi-2223 crystal structure. EDX results illustrate that the local elemental composition distributions of Nd atoms increase systematically depending on substitution level. However, it is noted that the replacement mechanism damages seriously fundamental electrical, superconducting, crystallinity and structural features. Dc electrical findings present that the superconducting and electrical properties reduce remarkably with the increment of aliovalent Nd/Sr substitution due to deviation in the mobile holes, in homogeneities of oxidation states in the copper-oxide layers, and formation of new internal and microscopic problems in the crystal system, confirmed by SEM examination. Besides, the characteristic transition temperatures diminish harshly from 116.59 K to 108.74 K for onset and 108.40 K until 78.81 K for offset transition temperature. The dramatic decrements stem from the degradation in bipolaron formations in the superconducting clusters, phonon modes and especially the gap coefficient. Similarly, the presence of Nd impurity damages the amplitude of pairing wave function. In fact, at maximum replacement level the ceramic compound exhibits a slight trace of pseudo-critical transition. The XRD results indicate that both the appearance or disappearance of characteristic diffraction peaks and the reduction of average crystallite size and c lattice cell constant confirm the reduction of high-T-c superconducting phase due to the suppression in the structural quality. The SEM pictures indicate that the appearances of surface morphology and crystallinity quality remarkably deteriorate depending on Nd/Sr replacement level as a consequence of non-uniform grain alignment distributions, structural problems, microvoids, internal defects, porosity, misoriented grain coalescences and micro crystals in the superconducting system. Additionally, the negative effect of Nd/Sr substitution is extensively discussed on the activation energy for the crystallization, thermodynamic stability, reaction kinetics, surface nucleation and growth mechanisms for the first time.

Automated summary

This paper provides a comprehensive characterization of Bi-2223 ceramic material with aliovalent Nd/Sr replacement, revealing that the replacement mechanism seriously damages the fundamental electrical, superconducting, crystallinity and structural features. The study shows that the substitution level affects the superconducting and electrical properties, characteristic transition temperatures, average crystallite size, and structural quality.