Contribution of domain wall motion to the permittivity of Rochelle salt

The contribution εw of the domain walls to the dielectric constant of Rochelle salt (sodium potassium tartrate) within the frequency region of 0.02 Hz and 50 kHz is studied. The dispersions of εw as well as their dependence on time are related to three electrical after effects already known, and which are characterized by the following activation energies: W1 = 0.51 eV, W2 = 0.66 eV, and W3 = 1.4 eV. A simplified model of the domain wall and its motion is proposed. Based on this model the time constants τi of the after effects and the thickness δ of the domain walls can be determined by measuring εw. In the ferroelectric range of temperature it follows for δ: 500 Å < δ < 2500 Å, and for the time constants 2 × 10−7s < τ1 < 5 × 10−2s and 5 × 10−4s < τ2 < 4 × 10−2s.