SOLIDIFICATION PROCESSING OF YBCO SUPERCONDUCTIVE OXIDE

Steady-state solidification processes of the crystal pulling method fo r single crystal production and unidirectional solidification by the z one melting method from the partial molten state for production of hig hly oriented polycrystalline crystals were reviewed. In the case of th e single crystal pulling, large faceted (1.45 cm x 1.45 cm x 13 mm) YB CO crystals are continuously pulled along either c-axis or a-axis at a bout 0.1 mm/h of the pulling rate. In the case of the zone melting, re sults indicated that higher G/R values were preferable for the continu ous growth. The sample grown at 1 mm/h possessed a large faceted solid /liquid interface and the volume fraction of 211 phase particles drast ically decreases from in the liquid to the 123 phase solids at the int erface. The result leads to the idea that the necessary solute for per itectic reaction is provided from 211 particles to 123 interface throu gh a liquid. Based on this idea, we developed a simple solidification model which is in good agreement with the experimental results.