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

Abstract

The phase diagram in the superconducting Bi 1.68 Pb 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+Ca 2 CuO 3 and 110 K phase+80 K phase) and a three-phase region (110 K phase+Ca 2 CuO 3 +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 Bi 1.68 Pb 0.32 Sr 1.75 Ca 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.