Electron Diffraction and Microscope Study of Ba-Nd-Cu-O Superconducting Oxides and Related Compounds

Four compounds within a range of solid solution Ba 2- x Nd 1+ x Cu 3 O y (where x ranges from 0 to 0.8) are examined by transmission electron microscopy. Ba 2 NdCu 3 O y , with T c = 83 K, has an ortho rhombic structure with twinned microstructure, similar to that of Ba 2 YCu 3 O y with T c = 90 K. Ba 1.8 Nd 1.2 Cu 3 O y , with T c = 45 K, and Ba 1.5 Nd 1.5 Cu 3 O y (nonsuperconductor) are both tetragonal, but the latter has a domain structure where the c axes of neighboring domains are perpendicular to each other. Ba 1.2 Nd 1.8 Cu 3 O y (nonsuperconductor) has a superstructure with A s =2 a , B s = b and C s =2 c . Two possible models of the superstructure are proposed.