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

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Abstract
Four compounds within a range of solid solution Ba2-x Nd1+x Cu3O y (where x ranges from 0 to 0.8) are examined by transmission electron microscopy. Ba2NdCu3O y , with T c= 83 K, has an ortho rhombic structure with twinned microstructure, similar to that of Ba2YCu3O y with T c= 90 K. Ba1.8Nd1.2Cu3O y , with T c= 45 K, and Ba1.5Nd1.5Cu3O y (nonsuperconductor) are both tetragonal, but the latter has a domain structure where the c axes of neighboring domains are perpendicular to each other. Ba1.2Nd1.8Cu3O y (nonsuperconductor) has a superstructure with A s=2a, B s=b and C s=2c. Two possible models of the superstructure are proposed.