Determination of Possible Maximum Critical Transition Temperatures with Empirical Model Depending on Structural Disorders-Defects for Bi2.1Sr2.0Ca1.1Cu2.0Oy System

Abstract

In this study, we find a strong link depending on the preparation annealing ambient conditions between structural disorders-defects and characteristic transition temperature parameters (offset, Tc offset and onset, Tc onset) of bulk Bi2.1Sr2.0Ca1.1Cu2.0Oy system for the first time. The superconducting samples are prepared at various annealing temperatures intervals 830°C -850°C with the temperature step of 10°C for annealing time ranging between 24 h and 48 h via traditional solid-state reaction route. The temperature-dependent resistivity measurements are conducted at temperature range of 30-140 K. The most ideal annealing ambient is obtained to be the combination of annealing temperature of 840 °C and annealing time of 24 h because of the enhancement in the formation possibility of strong cooper-pairs and optimization of itinerant charge carrier concentrations in the valence band. Similarly, the positive contributions are observed in the overlapping mechanism of wave functions between Cu-3d and O-2p electrons and especially logarithmic distribution of electronic state densities. The optimum annealing ambient makes the Bi-2212 system refine the structural problems and especially connectivity between the grains in the crystal structure. Conversely, the excess annealing ambient leads to increase considerably the grain misorientation, defects and grain boundary couplings due to the induced permanent problems in the crystal system. The highest correlated model shows that the Bi2212 superconducting compounds with the minimum structural disorders in the short-range-ordered antiferromagnetic Cu-O2 layers exhibit the maximum Tc onset and Tc offset values of about 85.347 K (R2 adj=0.9882) and 87.421 K (R2 adj=0. 97465).