A study of the relaxation of discommensurations in K2ZnCl4. II : Dielectric measurements at low frequency

The quasi-static dielectric constant and ferroelectric hysteresis in K2ZnCl4 were studied. In the virgin crystals, the dielectric constant exhibits a remarkable time-dependent variation during repeated temperature cycling and annealing. These results may be interpreted by assuming different nucleation probabilities of discommensurations (DC) in the virgin crystals and in those which had been heated to the incommensurate phase, and by considering the defect pinning of DC. It has also been found that the coercive field of the ferroelectric hysteresis exhibits a monotonic increase with time in the C phase. This is attributed to a gradual decrease of the DC density by vanishing of DC. With a model for the influence of crystal defects on the distribution of DC, the experimentally measured data have been well fitted.

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