Abstract:
The primary contributions of this study are not only to explore the role of diffusion annealing temperature interval 650 to 850 A degrees C on the formation of effective electron-phonon coupling or cooper-pair probabilities (percentage of clusters in the superconducting path), densities of active and dynamic electronic states at Fermi energy level, stabilization of superconductivity in the homogeneous regions, overlapping of Cu-3d and O-2p wave functions and bond strengths in the crystal matrix of Ni surface-layered Bi-2223 polycrystalline ceramics, but also to determine the temperature-dependent diffusion fast-rate and required minimum activation energy for the diffusion of Ni foreign impurities into the bulk Bi-2223 superconducting crystal structure for the first time. The dc electrical measurement results obtained show that the optimum diffusion annealing temperature is found to be 700 A degrees C for the penetration of optimum Ni concentration into the Bi-2223 crystal lattice so that the ceramic compound exposed to 700 A degrees C annealing temperature exhibits the highest electrical and superconducting properties. In this respect, the material with the minimum electrical resistivity parameters of Delta rho, rho (115K) , rho (res) and rho (norm) obtains the maximum superconducting characteristics of , and RRR. Accordingly, the annealing temperature of 700 A degrees C promotes the Bi-2223 ceramics for usage in the engineering, electro-optic, industrial and large scale applications. At the same time, the diffusion coefficients [D = D(o)exp(E/k(B)T)] determined at annealing temperature ranging from 650 to 850 A degrees C are observed to be much more significant at rather higher temperatures as compared to lower temperatures. The temperature-dependent Ni diffusion coefficient is determined to be D = 3.9707 x 10(- 7)exp[- 1.132 eV/k(B)T] for the Bi-2223 particulate solid material. Namely, the diffusion coefficient is calculated to be about 3.9707 x 10(- 7)cm(2) s(- 1) when the required minimum activation energy for the introduction of heavy metal Ni ions to the bulk Bi-2223 crystal structure is computed to be about 1.132 eV, being one of the most striking points deduced form this work.
