Microstructural study of the Ni-doped 2212-phase of BiSrCaCuO superconductor single crystals

The microstructure of Bi2Sr2Ca1Cu2-xNixOy (x = 0.0, 0.02, 0.04) single crystals grown by the travelling solvent floating zone method have been investigated using transmission electron microscopy, High-resolution observations and diffraction patterns at the [100] zone axis show a very small change in the direction of the modulation wave with increasing of Ni concentration. Streak-shaped diffuse scattering along the row of modulation reflections was observed in all the specimens. Convergent beam diffraction patterns at the [001] zone axis showed two distinct symmetries: either a very strong asymmetry or a weak asymmetry in the b-plane. The strong asymmetry was attributed to the presence of intergrowth layers on the c-plane. The positions of Ni atoms within the structure of the crystal and their influence on the electric resistivity was discussed by considering the present experimental observation results. (C) 1997 Elsevier Science B.V.