Grain size control in powder processed Y1Ba2Cu3Ox

Small grain size (123) material is produced in powder processing from Y₂O₃, BaCO₃, and CuO by avoiding liquid phases in the processing. Two techniques are shown to be effective (i) A stage-I air anneal at just below the 890°C eutectic between (123)-(011)-(001), followed by a stage-II oxygen anneal at temperatures ⩽930°C. Above 930°C a liquid phase forms which produces rapid grain growth. Preliminary data indicate that the liquid phase results from the same eutectic region in region A, which shifts to around 930°C in oxygen. (ii) Addition of (211) powder to the (123) mixture to maintain overall composition on the (211)-(123) tie line is also effective at reducing grain size by eliminating liquid phases. Maximum transport J_c values of around 600 A/cm² were obtained in the smallest grained material, ~2.5 μm, both with and without the (211) addition. The low values for the small-grain material are consistent with recent data showing that even low-angle grain boundaries in (123) material suppress transport currents