Further studies on the phase transformation in cadmium iodide polytypic crystals

Certain aspects of phase transformations in cadmium iodide polytypic crystals have been studied for the first time. It has been shown that the transformation of an ordered polytypic structure into another ordered structure is possible. This fact has been elucidated from the transformation 14H → 4H and 18H → 4H. Electron-microscope evidence for the occurrence of such transformations has been obtained. The phase transformations have also been viewed in the light of the structural geometrical schemes and of the stacking-fault energies of initial and transformed structures. Polytypic transformation from a rhombohedral to a hexagonal type has been observed, 42R→ 12H. Transformations involving poly types having similar stacking-fault configurations in their layer sequences have also been studied. The observed transformations of this type are 28H → 4H and 36H → 4H.