Superconductive YBa₂Cu₃O_7-x fibres from an extrudable dispersion of a particulate precursor

A particulate precursor of YBa₂Cu₃O_7-x was dispersed in a concentrated acetic/formic acid solution of yttrium, barium and copper acetates to form an extensible, viscous mixture. This dispersion was stable, unlike one prepared from superconductive YBa₂Cu₃O_7-x itself. Fibres extruded from the viscous dispersion were fired at 935 °C in the presence of oxygen. Although the fired fibres were not fully densified, they had a sharp Meissner transition temperature at 90 K and an apparent critical current density (J_c) of 900 A cm^-2 (1800 A cm^-2 corrected for porosity) at 77 K. The superconducting fibre was sensitive to magnetic field, which is evidence of weak coupling between the superconducting grains.