Diffusion in some high temperature super conducting cuprates

Following the Nobel prize winning discovery of J.G. Bednorz and K.A. Muller at IBM in 1986, the high temperature super conducting cuprates (HTSC) have been extensively investigated for their structure, fabrication and super conducting properties. Reasonable understanding of diffusion processes and of the atomic point defects has been reached through extensive experimental and theoretical investigations. Reliable diffusion data are now available in the published literature for the constituent cations and anion (O) species as well as some important impurity elements. These are compiled in this article and critically discussed. We have found that the YBa2Cu3O7-δ remains the best characterized and the most investigated material and hence it may be treated as a model to describe the diffusion and defect properties of the HTSC group of cuprates in general. Furthermore, information on self diffusion of Cu in YBa2Cu3O7-δ constitutes a basis for understanding of the relative diffusion behavior of other intrinsic (Y,Ba) and extrinsic (Ag,Co,Ni,Zn etc.) cations in HTSC cuprates. Extensive diffusion data of the anion (O) available in large number of HTSC cuprates have been gathered and examined for the underlying mechanisms. A semi-empirical relationship is shown to exist between the diffusion kinetics of Cu and oxygen in the HTSC cuprates in general. (author)