Diffusion in Some Perovskites: HTSC Cuprates and a Piezoelectric Ceramic

Abstract

Understanding of diffusion processes in perovskites, represented by the high-temperature superconducting (HTSC) cuprates and a piezoelectric ceramic, of all the constituent elements as well as of some foreign atomic species, is important for scientific as well as technological reasons. Self-diffusion of various cations and anion species in these compounds is a basic material property; it has an impact on the superconducting properties of the former and the physical response of the latter to electrical, mechanical, and thermal fields. The interplay of diffusion with the microstructures ultimately controls the reliability of the devices in actual applications. One good example is the control of twin-density and grain refinements accomplished recently through cation doping, which in some cases alleviates the flux-pinning problem in the matrix.[1] There are many situations in which cation diffusion manifests itself in the fabrication of HTSC elements. In the bulk production of tapes and wires produced by the oxide-powder-in-tube (OPIT) method, for example, silver sheath is typically used and the composite is subjected to severe thermomechanical deformation.[2] In such a fabrication process, silver sheath may partially dissolve in the fabrication process and reach the oxide core by diffusion, thereby reducing the current-carrying capacity of the connectors.