A flux technique which involved the use of a high temperature gradient was proposed for the growth of superconducting oxide crystals. It was concluded that the cooling rate had to be related to the crystal growth rate in order to obtain good-quality crystals. A model was presented which described the geometrical configurations and Burgers dislocation networks that were observed in the oxide single crystals. An orthorhombic-to-monoclinic phase transformation, with associated (100) twinning, was observed by means of transmission electron microscopy after annealing single crystals in vacuum (350 to 400C). It was proposed that this transformation involved O diffusion through the CuO2 planes, and subsequent O vacancy ordering.

G.Yang, J.S.Abell, P.Shang, I.P.Jones, C.E.Gough: Journal of Crystal Growth, 1996, 166, 820-4