Nucleation and Annihilation of Discommensurations in the First-Order Commensurate-Incommensurate Phase Transition in K2ZnCl4

The processes of nucleation and annihilation of discommensurations (DC's) in the first-order C-IC transition in K 2 ZnCl 4 have been studied by the measurement of the time evolution of the dielectric constant during the transition and by the observation of domain structure by etching, powder, replica and TEM techniques. In the C-to-IC transition, stripples are first nucleated at crystal defects and clusters of DC's expand from them one-dimensionally in the c -direction. The growth of the clusters results from the nucleation and growth of stripples along the boundaries of the clusters. The IC-to-C transition proceeds through the formation and growth of antistripples. Several stages of the domain pattern coarsening process have been revealed. A very complicated domain pattern with vortices is finally realized.