An environmental scanning electron microscope study of the Ag/Bi-2223 composite conductor from 25 to 840°C

An environmental scanning electron microscope (ESEM) equipped with a hot stage was used to examine phase evolution and microstructural transformations in a partially de-sheathed Ag/Bi-2223 composite conductor as it was heated from ambient temperature to well above 800 degrees C in an oxygen-containing environment. Coarsening of the powder, the opening and eventual filling in of gaps in the powder, recrystallization of the silver sheath, a granular-to-platy transition, platelet-like growth of the layered bismuthates, the formation and spreading of a transient liquid phase, and (at the highest temperatures) partial melting, accompanied by shifting of grain colonies, were all observed in the electron microscope images during various stages of the heating process. (C) 1999 Published by Elsevier Science B.V. All rights reserved.