PHASE-RELATIONS IN THE BI2O3-SRO-CUO SYSTEM AT 800-DEGREES-C

Phase relations in the Bi2O3-SrO-CuO system at 800 degrees C are presented. Several binary and ternary phases existing within this system have been identified and characterised by X-ray powder diffraction and density and overall oxygen content determination. Among them, particular 'A' and 'B' phases (both of variable composition) represent potential interest from the point of view of superconductivity. Evidence of the actual stoichiometry of the 2201-type superconductor (Tc=9-20 K) and of the most probable distribution of structural component atoms within its elementary unit subcell is given. A new interpretation of the general formula for the Bi-based superconducting cuprates has been proposed.