Improved processing of ceramic superconductors through low pressure calcination

This paper reports on vacuum calcination of precursor powder under controlled total oxygen pressure that has been investigated for synthesizing the superconductor YBa2Cu3Ox (YBCO). The reaction temperature, ∼800 degrees C, is ∼100 degrees C lower than that used in ambient-pressure calcination. Because a single calcination results in essentially phase-pure material, total calcination times have been drastically reduced. The particles of vacuum-calcined powder are finer and consequently have greater sinterability than powders made by conventional methods. Samples of YBCO made from this powder have critical current densities of ∼1000 A/cm2 at 77 K in a zero applied external magnetic field