Further studies on the dielectric behaviour of cadmium iodide polytypes

The dielectric constants (ɛ r ) of several cadmium iodide polytypes have been measured and found to be higher than that of the parent 4 H structure. The dielectric constants for several long‐period polytypes have been found to lie between 60 and 190 whereas the 4 H parent structure has a value in the range of about 15 to 30. In particular, both increasing polytype periodicity and increasing disorder increase the dielectric constant, e.g. from 16 for an ordered 4 H structure to 114 for a 32 H structure and 67 for a highly disordered 4 H structure. In the absence of disorder a particular polytype has its own characteristic dielectric constant value, e.g. the two 14 H polytypes which have a common ɛ r value of 63.