By analysing switching current data i(t), produced by the reversal
of domains, it was possible to extract detailed information concerning the
behaviour of the switching kinetics in TGS crystals. The switching curves were
fitted to a three-parameter nucleation and growth model based on Avrami
statistical theory. By direct observation of the domain pattern during slow
polarization reversal, by means of nematic liquid crystals, it was possible to
verify the assumptions of the theory for crystal samples with both a spatially
uniform and non-uniform distribution of domain nuclei.
Growth and shrinkage of domains in sodium nitrite crystals are investigated in a wide range of electric fields using the liquid crystal method. The rhombic shape of domains in the growing process and the lenticular shape of domains in the shrinking process are observed and discussed.
Ferroelectric switching in unipolar (CH3NH3)5Bi2Br11 crystal has been studied by optical observation of the domain structure in low electric fields and switching current registration in high fields. We discuss investigations on the temporal behaviour of the electric polarization in static electric fields as well as polarization decay after removal of the electric field. The backswitching process appears to have a correlation to a defect-induced internal field in the crystal. For the interpretation of experimental data we utilize the classical nucleation and growth model of phase transformation (e.g. Avrami–Kolmogorov theory). An analysis assuming a statistical distribution of the characteristic domain growth times is proposed to explain and to find the functional form of the experimental data.
The influence of Ni doping on the ferroelectric and dielectric properties have been examined in Sr 0.61 Ba 0.39 Nb 2 O 6 (SBN:61) relaxor crystals. The dopants introduced into SBN:61 crystals promote the switching process by reducing the value of threshold nucleation field, and thus coercive field. We present real-time studies of domain nucleation and growth processes in doped SBN:61 by the nematic liquid crystal (NLC) decoration technique. The broad phase transition and low-frequency dielectric dispersion that are exhibited by doped SBN:61 samples have a strong link to the configuration of the ferroelectrics microdomains, which in turn is strongly determined by Ni ions concentration.
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