A PHASE-DIAGRAM OF THE BI2SR2CUO6-CACUO2 SYSTEM IN RELATION TO BI-BASED SUPERCONDUCTORS

A pseudo-binary phase diagram of the Bi2Sr2CuO6 (Bi-2201)-CaCuO2 syste m between 850 and 1020 degrees C is prepared by a simultaneous use of a newly developed high-temperature X-ray powder diffraction apparatus with a rapid counting system and an optical microscope. The phase diag ram is characterized as: (1) a complete liquid state exists above 911 degrees C between the compositions of Bi-2201 and Bi2S2CaCu2O8 (Bi-221 2); (2) the incongruent melting point of Bi-2212 is 887 degrees C, whi ch is the lowest in this system; (3) Bi-2212 changes into a mixture of (Sr,Ca)CuO2, Bi-2201 and liquid above this point with a very low tran sformation rate; and (4) a mixture of Bi-2212, Ca2CuO3 and few Bi2Sr2C a2Cu3O10 (Bi-2223) having the nominally stoichiometric Bi-2223 composi tion melts partially at 896 degrees C and becomes (Sr,Ca)CuO2, (Sr,Ca) (2)CuO3 and liquid. (C) 1998 Elsevier Science B.V. All rights reserved .