Improvement in fundamental electronic properties of Bi-2212 electroceramics with trivalent Bi/Tm substitution: a combined experimental and empirical model approach

摘要

This study delves into the variation in the fundamental aspects of electrical quantities with the partial substitution of Tm impurities at Bi-site in the Bi_(2.1-x)Tm_xSr_(2.0)Ca_(1.1)Cu_(2.0)O_y (0.00 ≤ x≤ 0.30) ceramic system with the derivatives of electrical resistivity examinations and theoretical approaches. It is found that all the electrical characteristic properties tend to improve with the trivalent Bi/Tm substitution level up to x = 0.07 beyond which they degrade considerably due to the increment of non-superconducting barrier regions, permanent disorders, inhomogeneity, porosity, grain misorientation distribution, internal and surface omnipresent defects, microscopic cracks, and coupling interaction problems throughout the grain boundaries in the Bi-2212 crystal system. Thus, the optimum dopant level of x = 0.07 results in the transition from the over-doped state to optimally doped state in the Bi-2212 crystal system as a consequence of augmented hybridization mechanism. Further, the characteristic two-stage transition temperatures, gap coefficient, Josephson coupled, and thermal energies for the isolated grains and inter-grains are explored. The findings show that the optimum Bi/Tm substitution leads not only to stabilize the superconductivity in the homogeneous superconducting clusters as a result of the increment in the formation of active Cooper pairs but also to decrease significantly the location of resistivity in long-range coherent state due to the increment of hole trap energy. Additionally, a strong link is established between the structural disorders-defects and onset/offset (T_c~(onset)/T_c~(offset)) transition temperatures using the electrical resistivity features for the first time. The empirical model based on the impurity scattering and lattice strain in the crystal lattices displays that it is possible to achieve the possible highest T_c~(onset) and T_c~(offset) values of about 86.558 K and 86.445 K, respectively. To sum up, the paper with strong methodology between electrical quantities and structural disorders-defects depending on Tm impurity may be a pioneering research to explain why the characteristic features improve with the optimum substitution and especially open up a novel and feasible area for the advanced engineering, heavy industrial technology, and large-scale applications of ceramic materials.