Phase relations in the Bi₂O₃-SrO-CuO system at 800 degrees C

Abstract

Abstract. Phase relations in the Bi,O,SrO-CuO system at 800°C are presented. Several binary and ternary phases existing within this system have been identified and characterised by x-ray powder diffraction and denslty 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 (T, = 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.

High temperature phase equilibria studies in the Bi-Sr-Ca-Cu-O-Ag system

“…xCax) 203-x (0.2<x<.25) CuO-SrO [34,35,44,46,49] There are three known compounds in the CuO-SrO system. Sr2Cu03 is orthorhombic (Immm) and stable up to 1220°C.…”

“…SrCuOa is also orthorhombic (Cmcm) and is stable up to 1080°C. A recently discovered face centered orthorhombic phase has been identified in the literature as Sr3Cu508 [49] or Sr4Cu70i2 [35]. There is now general agreement that the actual stoichiometry of this phase is Sri4Cu2404i.…”

Constitution of Bi2(Sr1-xCax)2Cu2Oyand of Bi8(Sr1-xCax)8Ca4Cu10Oytype solid solutions

“…The series of solid solutions available from [l] were enriched with some further samples, synthesised following the procedure described in [2]. However, this time the samples were subjected to additional heat treatment at different temperatures for different durations (see table 1).…”

Determination of phase diagram cuts in the system

“…Studies aimed at the Bi-Sr-Cu-O system have led to the delimitation of the concentration region of the Bi 2+x Sr 2−y CuO 6+γ phase stability (see e.g. [1][2][3]) and of the solid-liquid boundaries in the temperature range of 800-880 • C [4]. In contrast to this, the knowledge of the phase equilibria in the more complicated Bi-Sr-Ca-Cu-O system containing the 2212 and 2223 phases has remained until the present time limited to the subsolidus region [5][6][7].…”