Improved processing of ceramic superconductors

Vacuum calcination of precursor powder under controlled total oxygen pressure has been investigated for synthesizing YBa{sub 2}Cu{sub 3}O{sub x} (YBCO) superconductor. The reaction temperature, {approximately}800{degree}C, is {approximately}100{degree}C lower than that used in ambient-pressure calcination. Since a single calcination results in essentially phase-pure material, total calcination times have been drastically reduced. The vacuum-calcined powder has finer particles and consequently greater sinterability than powders made by conventional methods. Samples made from this powder have critical current densities of {approximately}1000 A/cm{sup 2} at 77 K in zero applied external magnetic field. 14 refs., 4 figs.