Determination of optimum diffusion annealing temperature for Au surface-layered Bi-2212 ceramics and dependence of transition temperatures on disorders

Abstract This study aims not only to declare experimentally the effect of diffusion annealing temperature (600 °C-850 °C) on the crystal structure, electrical and superconducting properties of Au surface-layered Bi-2212 ceramics by dc resistivity and powder X-ray diffraction measurements, but also to advance in-depth understanding of empirical relationship between the disorders and transition temperatures. It is found that the diffusion annealing temperature of 800 °C is found to be optimum for the improvement of crystal structure due to the retrogression of disorders and local structural-distortions in the layers, increasing metastability, σ-gap anisotropy and softening of Ag and B1g phonons. Accordingly, the Au nanoparticles transit from inherently over-doped nature of the compound to optimally-doped state. Additionally, the empirical relations between critical temperatures and Δ ρ parameters (related to disorders) show that it is possible to achieve maximum onset and offset critical temperature values of 90.467 K and 90.359 K for the Bi-2212 ceramics.