Synthesis of ceramic superconductors under low oxygen pressure

We have developed a process for synthesizing orthorhombic YBa₂Cu₃O _x (123) superconducting powders by calcination of the precursor powder under reduced total oxygen pressure. Because a single calcination at 800°C for 4 h in flowing oxygen at a pressure of 2 mm Hg results in essentially phase-pure material, total calcination times have been drastically reduced. At liquid nitrogen temperature, sintered pellets made from this powder have critical current densities of ∼1000 A/cm² in zero applied magnetic field.