The Location of Hysteresis Phenomena in Rochelle Salt Crystals

Abstract

Measurements of the elastic properties of an unplated crystal, the piezoelectric constant $f_{14}$, and the clamped dielectric constant of a Rochelle salt crystal show that practically all hysteresis and dissipation effects are associated with the clamped dielectric properties of the crystal. A theoretical formulation of the equations of a piezoelectric crystal has been made which takes account of the dissipation effects. The formulation is given for the polarization theory. The frequency variation of the clamped dielectric constant when interpreted by Debye's theory of dielectrics, modified to take account of hysteresis losses, indicates that there are two components, one of which has associated with it at high viscous resistance, whereas the other one does not. The nonviscous component has a dielectric constant of about 100 at 0°C and is probably due to the displacement of the ions in the lattice structure. The viscous component has a dielectric constant of about 140 at 0°C and is probably due to the dipoles of the Rochelle salt. Both components have higher dielectric constants and hysteresis between the Curie points indicating a cooperative action of the molecules for both components in this temperature region.