Abstract
The intercalation of CuO layers in the 123 compound is analysed in terms of the movement of partial dislocations in the matrix, assisted by CuO diffusion. The influence of an external stress on the nucleation of such a CuO layer in a perfect or in a dislocated crystal is discussed. A model of a partial dislocation Frank-Read source, diffusion assisted, is proposed for the formation of polytypoids.