Y-Based Superconductors

Yttrium-barium-copper oxide compounds YBa2Cu306+x (x = 0.6-1), generally abbreviated to 123, with a Tc of 90K which is above the temperature of liquid nitrogen, are of great importance (2). As noted earlier, Tc is governed principally by the crystal structure 

Quantification of Chemical Composition analyses Spectra normalized to CuKa Peak  

A number of models have been proposed to explain the crystal chemistry associated with the structural modulations. The following paragraphs survey the current understanding of the origin of the modulations  

Interpretations of Structural Modulations The following paragraphs summarize the reported models concerning the origin of the modulations and report some of the recent experiments. The origin of the modulations, the role of anion stoichiometry and of the cation substitution affecting the modulations and Tc are not yet fully resolved and need further experimental clarification. 

Although the full implications of these data are yet to be analyzed, it seems likely that the lattice or size mismatch between the Bi-O and the perovskite layers plays a key role in constituting the 

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