Morphological Stability of Sm123 Superconductor during Peritectic Solidification from Sm211 + L Mixture

The interface stability of the Sm 123 superconductor was analyzed in accordance with the constitutional undercooling criterion. As the singlecrystal growth of the 123 phase is largely dependent on the growthinterface stability, a quantitative analysis was very much required. From this analysis, it was clarified that the constitutional undercooling must exist in the liquid when the 123 growth interface comes close to a 211 particle during the peritectic solidification. It was also predicted that the larger 211 particle radius, smaller volume fraction of the 211 particles, larger growth rate, or smaller imposed temperature gradient would cause easy occurrence of the constitutional undercooling ahead of the 123 growth interface. Taking into account the nucleation at the L/211 interface just ahead of the 123 growth front due to the constitutional undercooling, the transition of 123 growth from a planar-interface morphology to an equiaxed blocky morphology was investigated quantitatively and qualitatively.