Phase relations at 850°C and 870°C, and melting transitions in air, oxygen, and helium have been studied for Bi2.1Sr1.9CuO6 and for the series Bi2Sr2Can-1CunO2n+4 for n=1, 2, 3, 4, 5 and ∞ ("CaCuO2"). Up to 870°C, the n=2 composition resides in the compatibility tetrahedron bounded by Bi2+x(Sr, Ca)3-yCu2O8, (Sr, Ca)14Cu24O41. Ca2CuO3, and a BiSrCaO phase. The n ≥ 3 compositions reside in the compatibility tetrahedron Bi2+x(Sr, Ca)3-yCu2O8(Sr, Ca)14Cu24O41 Ca2CuO3CuO up to 850°C. However, Bi2+x(Sr, Ca)4-yCu3O10 forms for n ≥ 3 after extended heating at 870°C. Bi2+xSr2-yCuO 6 (i.e. the Ca-free, very low-Tc phase) melts in air at 914°C, while the Bi2+x(Sr, Ca)3-yCu2O8 composition that coexists with (Sr, Ca)14Cu24O41, Ca2CuO3, and CuO melts at 895°C. During melting, all of the compositions studied lose 1-2% by weight of oxygen from the reduction of copper.
|Original language||English (US)|
|Number of pages||14|
|Journal||Physica C: Superconductivity and its applications|
|State||Published - Sep 1 1991|
Bibliographical noteFunding Information:
This work was supported in part by the NASA/ ASEE summer internship program, and by NASA Cooperative Agreement NC 3-129. The work of V. Finan was supported by NSF REU grant no. DMR 88-05106. The authors thank Ralph Garlick f,~r per-