Phase relations in the Bi-Sr-Ca-Cu-M-O (M = Y, Dy, Ho, Er, Tm, Yb, Lu) systems

The phase relations in the Bi-Sr-Ca-Cu-M-O (M = Y, Dy, Ho, Er, Tin, Yb, Lu) systems near Bi2Sr2CaCu2O8+x (Bi-2212) were studied between 850 and 990 de greesC. The results demonstrate that larger sized rare earths (Y, Dy, Ho, E r) substitute on the Ca site in Bi-2212, leading to the formation of CaO. S maller sized rare earths (Tin, Yb, Lu) replace lesser amounts of Ca and for m Sr2MBiO6 phases. In the material of nominal composition Bi2Sr2Ca0.85M0.15 Cu2O8+x + 0.25Sr(2)YBiO(6) prepared via melt processing, a major fraction o f the Y atoms substitute for Ca in Bi-2212, resulting in a low-T-c multipha se superconductor. In the analooousYb system, a Bi-2212-Sr2YbBiO6 composite with T-c = 87 K is obtained.