Piezoelectric resonance in Rochelle salt: The contribution of diagonal strains

Within the framework of two-sublattice Mitsui model with taking into account the shear strain ε₄${\epsilon }_4$ and the diagonal strains ε₂${\epsilon }_2$ and ε₃${\epsilon }_3$, a dynamic dielectric response of Rochelle salt X-cuts is considered. Experimentally observed phenomena of crystal clamping by high frequency electric field, piezoelectric resonance, and microwave dispersion are described. Analytical expressions for the resonant frequencies of these cuts, associated with the shear vibration mode of ε₄${\epsilon }_4$ and with the extensional in-plane modes of ε₂${\epsilon }_2$, ε₃${\epsilon }_3$, are derived. It is shown that the lowest resonant frequency is always associated with the ε₄${\epsilon }_4$ shear mode.