A SYSTEMATIC STUDY OF BI2-XPBXSR2CA2CU3OY PHASES (O LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO 2)

By means of X-ray diffraction, electron diffraction and scanning electron microscopy, we have observed that for low Pb/Bi ratios lead incorporates into the structure of the so-called 80 K and 110 K Bi-superconductors, which normally coexist. However, the 2223 superconducting phase, which shows zero resistance at a temperature as high as 110.7 K, becomes predominant as the sintering time increases. From x=0.5 upwards an almost Bi-free second phase appears. It is non-superconducting and its structure appears to be hexagonal. Some Ca2PbO4 is also present for x > 0.5. © 1990.