Structural changes in melt-processed high-T{sub c} cores of composite wires

In a number of works, melting and subsequent controlled solidification were reported to enhance the critical current density of high-T{sub c} ceramics by several orders of magnitude. These studies, however, dealt with platelike samples only. As distinct from earlier works, the authors studied directional solidification of a high-T{sub c}YBa{sub 2}Cu{sub 3}O{sub 7-x} material in the form of a metal-sheathed ceramic core of composite wire. In order to melt the ceramic core, the metallic sheath of the composite wire was heated resistively. By adjusting the wire diameter and sheath thickness and resistivity, it was possible to heat the sheath to above the melting point of the ceramic core (1000 - 1100{degrees}C) and to maintain the temperature for some time in order to melt the ceramic core. A gradual reduction in the current intensity ensured controlled solidification of the melt. The objective of this work was to study the structural and superconducting properties (T{sub c} and j{sub c}) of melt-processed YBa{sub 2}Cu{sub 3}O{sub 7-x} ceramic cores of composite wires.