ORIGIN OF SUBGRAIN STRUCTURE WITHIN A DOMAIN IN MELT-PROCESSED YBA2CU3O7

The microstructures of melt-processed YBa2Cu3O7 with different cooling rates were studied by polarized light optical microscope. The present study concentrated mainly on the origin of subgrain structure within domains, where there exist controversies in the literature, as due to the polygonization process in the solid state or during the crystalliz ation process. The present study strongly supports the view that subgr ains result from the solidification instabilities during crystallizati on from the melt rather than due to the polygonization process in the solid state.