Single High-Tc Phase Region of the Bi-Pb-Sr-Ca-Cu-O System

Abstract
The phase diagram in the superconducting Bi1.68Pb v Sr x Ca v Cu z O w (v=0.28, 0.32) system was investigated by means of X-ray diffraction and electrical resistivity for samples calcined in air. The results revealed that the phase was classified into four regions, a single 110 K-phase region, two types of two-phase regions (110 K phase+Ca2CuO3 and 110 K phase+80 K phase) and a three-phase region (110 K phase+Ca2CuO3+80 K phase). The single 110 K phase with a T c of about 106–108 K exists in a fairly wide composition range, especially in the Bi1.68Pb0.32Sr1.75Ca y Cu z O w system, 1.75≦y≦1.85 and 2.65≦z≦2.85. This means that the single 110 K phase can be easily obtained, even by the usual calcination in air in the Bi-Pb-Sr-Ca-Cu-O system.

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