Stoichiometry and kinetics of formation of Bi2Sr2CaCu2O? solid solutions
- 1 January 1992
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of Materials Chemistry
- Vol. 2 (5) , 579-580
- https://doi.org/10.1039/jm9920200579
Abstract
Single-phase samples of the ‘90 K’ BiSCCO superconductor can be prepared, by careful attention to the experimental conditions, for the compositions: (a) stoichiometric Bi2Sr2CaCu2Oδ(b) Bi2+X Sr2–X CaCu2Oδ 0 < X ⩽ 0.2; (c) Bi2Sr2–y Ca1–y Cu2 Oδ, 0 < y⩽ 0.5: (d) Bi2+x Sr2–x–y Ca1 +y Cu2Oδ, all of which retain the same (Bi + Sr + Ca) : Cu ratio of 5 : 2 as the ideal ‘2212’ Stoichiometry. The ranges of x and y values for the solid solutions are given in the form of a pseudoternary phase diagram. Lattice parameters were indexed on a tetragonal cell; a was independent of composition; c decreased with both x and y. Formation rates of the 90 K phase vary greatly with composition and generally increase with both x and y. The stoichiometric composition requires typically 5 days at 860 °C for complete reaction, whereas the composition x= 0, y= 0.5 requires only 2 days at 820 °C.Keywords
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