The dynamics of polarization reversal in sinusoidal fields (0.1Hz less
than or equal to f less than or equal to 50kHz) was studied in the fe
rroelectric lock-in phase of purified Rb2ZnCl4 crystals. The frequency
dependence of remanent polarization and coercive field E-c is qualita
tively the same above and below Tapproximate to 160K, where for all m
easuring frequencies E-c starts to increase rapidly with decreasing te
mperature. A model which treats sideways shifts of planar, nearly regu
larly arranged domain walls as the only mechanism of polarization reve
rsal in Rb2ZnCl4 is applicable for the quantitative description of fer
roelectric hysteresis loops in the whole temperature interval under in
vestigation. The anomalous increase of E-c at T seems to be connected
to a corresponding increase of the viscosity coefficient.