Thermal instability of (Bi;Pb)2Sr2Ca2Cu3Ox in contact with silver

The chemical and microstructural evolution of particulate (Bi, Pb)2223 in contact with pure bulk silver at 830 to 905 ampersand hthinsp;degree C under flowing air and Ar - 5% O2 atmospheres has been studied. Specimens annealed under PO2 and temperature conditions for which the (Bi, Pb)2223 phase itself is stable, based on a critical assessment of the literature, revealed a silver/(Bi, Pb)2223 interface-limited reaction, producing both solid and liquid decomposition phases. The (Bi, Pb)2223 not in direct contact with silver exhibited no reaction under the same conditions. Solid silver dissolves into the (Bi, Pb)2223 incongruent liquid, facilitating the incongruent melting reaction. On cooling, equiaxed metallic silver particles precipitated uniformly throughout bulk specimens partially melted on a silver substrate. copyright 1999 Materials Research Society