The growth characteristics of single crystals with a shape memory effect

Using the Bridgman technique the growth characteristics of single crystals with a shape memory effect have been studied in detail. The experimental results show that there is a critical growth velocity for the chosen material. If the growth velocity is below this critical value, then a single crystal can be grown-otherwise a polycrystal will be formed; the critical growth velocity is dependent on: (i) the diameter of the grown crystal, (ii) the purity and form of the raw materials used, and (iii) the temperature gradient in the oven used for single-crystal growth. An empirical formula is proposed for those dependences. Good homogeneous single crystals with carefully controlled compositions can be obtained by choosing suitable growth parameters in particular, an appropriate growth velocity.