The twin-boundary characteristics of melt-textured samples were investigated by means of transmission electron microscopy. Stoichiometric Cu3Ba2YO7, Y2CuBaO5 phase-doped Cu3Ba2YO7 and Cu3Ba2YO7 doped with Y2CuBaO5 and Pt were studied. The Pt led to a sharp decrease in the b/a ratio and its orthorhombicity. It was concluded that Pt substituted for Cu atoms in the CuO chains. The thickness of the twin boundary layer decreased with decreasing O content and Pt doping. Two different types of twin boundary were observed which differed with regard to their interfacial energy and structure. The twin spacing decreased with the size of the twin domains. The domain size was strongly affected by the density of Y2CuBaO5 inclusions, which acted as nucleation centers for twin formation.

D.Müller, H.C.Freyhardt: Philosophical Magazine Letters, 1996, 73[2], 63-70