Domains of existence and physical properties of the 2201- and 2202-type structure phases in the Bi₂O₃-SrO-CaO-CuO quaternary system

Abstract

The domains of existence of the 2201- and 2202-type structures in solid solutions of the Bi2O3-SrO-CaO-CuO quaternary system are investigated from the powder X-ray diffraction, density and resistive transition measurements. It is shown that the general formula of Torardi (1988) should not be identified as describing fixed stoichiometry of Bi-based compounds but as a code according to which the unit cells are to be constructed. The authors have also shown that the composition of the investigated phases can vary within some region of homogeneity. The 2201-type structure acts as a matrix for the formulation of new phases by addition of some quantities of calcium and copper, which are known as 80 K and 110 K superconductors. The influence of oxygen on the properties of Bi-based compounds is also evaluated.

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

“…To our knowledge (see for instance [30]) in real samples they may play an important role. Further evidence on this problem will be given in an accompanying paper [31].…”