A study of the relaxation of discommensurations in K2ZnCl4III. Measurements of the complex dielectric constant

For pt.II see ibid., vol.4, p.6899 (1992). Dynamics of discommensurations (DC) in the incommensurate-commensurate transition at T C in K 2 ZnCl 4 were studied. Slow relaxation processes are revealed by an investigation of the frequency-dependent complex dielectric constant. The occurrence of a polydispersion indicates that in the vicinity of T C there exists a transient chaotic state with an inhomogeneous distribution of DC. By fitting the experimental data, the authors found that there exist two characteristic relaxation frequencies during the C-I transition. One corresponds to the regions of the frozen-in state of the C phase, the other to the regions with DC newly created from the C domains of the crystal. This indicates the coexistence of the C and I phases near T C . The results reveal that the phase transformation proceeds through the nucleation of DC stripples and through the rearrangement of both the newly created DC and the 'frozen-in' ones.