Time Evolution of the Incommensurate Phase in K2ZnCl4 Observed by Dielectric Measurements and X-Ray Scatterings

At the incommensurate-commensurate transition in K 2 ZnCl 4 , slow time variations of the dielectric constant ε and the satellite reflectins were observed. With increasing temperature, the incommensurate satellites appeared and coexisted with the commensurate ones when ε began to rise up, and the commensurate ones disappeared when ε became maximum. On cooling, the peak of ε corresponded to the appearance of the commensurate reflections. In both incommensurate and commensurate phases, the slow relaxation of ε accompanied with the change of the mean modulation period and the regularization of the modulated structure. The misfit parameter approached the steady value very slowly with a logarithmic dependence on time at later stage.