Microstructure and properties of the ∼90-K superconductor Bi2Sr3−xCaxCu2O8+δ

Abstract

Phases with superconducting onset temperatures of 60, 87, and 112 K have been identified in the new superconductor ${\mathrm{Bi}}_2{\mathrm{Sr}}_{3-x}{\mathrm{Ca}}_x{\mathrm{Cu}}_2{\mathrm{O}}_{8+\delta }$. The microstructures of two crystal types, one associated with the 87- and 60-K phases, and the other probably with the 112-K phase, have been examined by electron microscopy. The first crystal type has a superlattice structure which is incommensurate for the lower-temperature preparations. The second type of crystal, which forms at higher temperatures, has no superlattice structure.