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 $\varepsilon_4$ and the diagonal strains $\varepsilon_2$ and $\varepsilon_3$, 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. It is shown that the lowest resonant frequency is always associated with the $\varepsilon_4$ shear mode 
A. P. Moina
cond-mat.mtrl-sci