Structure and the (014)/(005) X-Ray Line Intensity in 1-2-3 Superconductors

The discovery of high Tc superconductivity in the La-Ba-Cu-O system [1] initiated an accelerated interest in this and related systems. To date the highest zero resistance temperatures have been observed in compounds of the form R1Ba2Cu3O9-δ where R = Y, Nd, Sm, Eu, Gd, Ho, Er, and Lu. [2–6] The Y1Ba2Cu3O9-δ compound has been studied extensively by x-ray diffraction [7–11] neutron scattering [12, 13] and thermogravimetric analys is. [2, 4] The unit cell is found to have a sequential Ba-Y-Ba stacking, an ordered oxygen deficiency, [13] and a slight orthorhombic distortion. [7–11] The similarity of the x-ray diffraction data and lattice constants of the compounds in this series strongly indicates that these compounds have the same structure, with the specific rare earth element simply substituting for Y.