Effect of oxygen partial pressure on the transformation between high T c and low T c phases in a Bi-Pb-Sr-Ca-Cu-O system

Abstract
The effect of oxygen partial pressure on the stability of the high Tc phase (>100 K) in a Bi‐Pb‐Sr‐Ca‐Cu‐O system has been studied using resistivity, x‐ray diffraction, and ac susceptibility measurements. It was observed that part of the high Tc phase formed by sintering at 840 °C in a low oxygen partial pressure of 1/10 atmosphere was transformed into a low Tc phase (∼80 K) and an insulating phase by heating at the same sintering temperature in O2 of one atmosphere. The original high Tc phase was restored upon retreatment at the same temperature in a low oxygen partial pressure of 1/10 atmosphere.