Preparation of High-Tc (110 K) Superconducting Phase by the Annealing of Low-Tc (80 K) Superconductor Bi2(Sr0.5Ca0.5)3-xCu2Oy

Abstract
The high-T c (110 K) superconducting phase of Bi-Sr-Ca-Cu-O system is obtained by the transformation of the low-T c (80 K) phase, Bi2(Sr0.5Ca0.5)3-x Cu2O y [x=0, 0.1, 0.2, 0.4] through long time sintering. One sample with x=0.4 whose sintering temperature is 868°C shows zero resistivity at 106 K and a sharp onset of the diamagnetic susceptibility. The Meissner signal reaches about 30% of the ideal value at around 100 K. The relation between starting composition and the process of the formation of the 110 K phase is briefly discussed, based on the results of ac and dc magnetic susceptibility measurements.