Crystallization of a Rapidly Quenched High T sub c Bi-Containing Glass Composition.

A pure composition Bi sub 4 Sr sub 3 Ca sub 3 Cu sub 4 O sub (16-delta) was made by twin roller quenching from the melt at 975 to 1075C at a quench rate of about 10 sup 7 K sec (- 1). Differential thermal analysis in oxygen and nitrogen showed a glass transition at 410C followed by a strong exotherm, occurring at 460C in oxygen. Despite this apparent crystallization, X-ray diffraction showed only broad peaks attributable to short- range-order only. After additional exothermals the single- copper-oxide-layer compound Bi sub 2 (Sr, Ca) sub 2 CuO sub 6 appeared in X-ray diffraction after annealing above 630C; this phase changed gradually to the expected double-copper- oxide-layer high-T sub c superconductor as the annealing temperature approached the melting point.