BULK MANUFACTURE OF YBCO POWDERS BY COPRECIPITATION

This work presents an assessment of the coprecipitation technique for the reliable production of high-temperature superconducting (HTS) copp er-oxide powders in quantities scaled up to 1 kg. This process affords precise control of cation stoichiometry (< 4% relative), occurs rapid ly (almost instantaneously) and can be suitably developed for large-sc ale (e.g. tonne) manufacture of HTS materials. The process is based up on a simple control of the chemistry of the cation solution and precip itation with oxalic acid. This coprecipitation method is applicable to all copper-oxides and has been demonstrated in this work using over t hirty separate experiments for the following compositions: YBa2Cu3O7-d elta, Y2BaCuO5 and YBa2Cu4O8. The precursor powders formed via this co precipitation process are fine-grained (approximately 5-10 nm), chemic ally homogeneous at the nanometer scale and reactive. Conversion to ph ase-pure HTS powders can therefore occur in minutes at appropriate fir ing temperatures.