Jc-B characteristics of silver sheathed oxide superconductors

Thermogravimetry, differential thermal analysis, and magnetization measurements on powders and silver-sheathed Y_1-xCa_xBa₂Cu₄O₈ (x=0 and 0.1) were carried out. The deoxidation temperature of the Ca-doped Y124 materials in the silver-sheathed wires increased from 775°C to 845°C with increasing oxygen partial pressure (P_O2 ) from P_O2=0.2 bar (in air) to PO₂=1.0 bar (in pure oxygen). Although the critical transport current density of 2.1×10⁴ A/cm² was observed for silver-sheathed Y(Ca)124 wire at 4.2 K and 0 T by selecting the oxygen partial pressure and the annealing temperature the grain boundary coupling was found to be inefficient by AC susceptibility measurement. A partial melting and growth technique was applied to silver-sheathed Bi2212 wires and well oriented and contacted grains aligned parallel to the silver wall were obtained