Solidification Processing of YBCO Superconductive Oxide.

Steady-state solidification processes of the crystal pulling method for single crystal production and unidirectional solidification by the zone melting method from the partial molten state for production of highly oriented polycrystalline crystals were reviewed. In the case of the single crystal pulling, large faceted (1.45 cm×1.45 cm×13 mm) YBCO crystals are continuously pulled along either c-axis or a-axis at about 0.1 mm/h of the pulling rate. In the case of the zone melting, results indicated that higher G/R values were preferable for the continuous growth. The sample grown at 1 mm/h possessed a large faceted solid/liquid interface and the volume fraction of 211 phase particles drastically decreases from in the liquid to the 123 phase solids at the interface. The result leads to the idea that the necessary solute for peritectic reaction is provided from 211 particles to 123 interface through a liquid. Based on this idea, we developed a simple solidification model which is in good agreement with the experimental results.