The microstructures of Cu3Ba2YO7-Y2BaCuYO5 melt-textured composites which had been deformed into the secondary and tertiary creep regimes were investigated by means of transmission electron microscopy. A high density of Y2BaCuYO5 precipitates played an important role as pinning sites for gliding dislocations. In the secondary regime, trapped dislocations dissociated to leave a stacking fault with a displacement vector of [1/2-δ0(1/3)]. A second stacking fault, 1/6<301>, tended to be associated with the former stacking fault. In this stage, deformation was dominated by diffusion between precipitates that were interconnected by trapped dislocations. In the tertiary stage, dislocation multiplication was the main factor which controlled the microstructure. This was characterized by a marked increase in the density of perfect dislocations with Burgers vectors of <100> and <110>. It was noted that oxygenation, performed at 450C, led to a marked modification of the as-deformed microstructure.

Evolution of the Microstructure during High-Temperature Creep and Oxygenation in Directionally Solidified YBa2Cu3O7-x. N.Vilalta, F.Sandiumenge, J.Rabier, M.F.Denanot, X.Obradors: Philosophical Magazine A, 1997, 76[4], 837-55