Superconductivity of Bi0.25-ySr0.25-yCa2yCu0.5Ox (y=0.1, 0.125, 0.15)

Abstract

Resistivity and magnetic susceptibility of superconducting Bi_0.25-y Sr_0.25-y Ca_2y Cu_0.5O _x (y=0.1, 0.125, 0.15) have been measured and compared with the results of X-ray powder diffraction. The volume fraction of the low-T _c phase (T _c∼75 K) decreases as the Ca concentration is increased and superconductivity attributed to the high-T _c phase (T _c>100 K) is observed. Resistivity of Bi_0.125Sr_0.125Ca_0.25Cu_0.5O _x shows a sharp transition above 100 K and becomes zero at 97 K.