Antiferroelectricity in pure ferroelastics

In pure ferroelastics, the coupling existing under applied electric field between spontaneous strain and electric polarization is shown theoretically to transform the paraelastic and ferroelastic phases into polarized phases. This effect is rooted in the existence in the zero-field crystal structure of most ferroelastics of polarizable crystallographic sites forming an antiferroelectric array of dipoles. Under high fields the polar ferroelastic phase can become ferroelectric across a first-order isostructural transition, which exhibits a double hysteresis loop.