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How does an electric field change the dimensions of a piezoelectric ceramic?

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Figure 1: Ferroelectric properties of barium titanate (BaTiO3). (Left) Above 120° C the structure of the BaTiO3 crystal is cubic, and there is no net polarization of charge; (right) below 120° C the structure changes to tetragonal, shifting the relative positions of the ions and causing a concentration of positive and negative charges toward opposite ends of the crystal. — capacitor dielectric and piezoelectric ceramics Figure 1: Ferroelectric properties of barium titanate (BaTiO₃). (Left) Above 120° C the structure of the BaTiO₃ crystal is cubic, and there is no net polarization of charge; (right) below 120° C the structure changes to tetragonal, shifting the relative positions of the ions and causing a concentration of positive and negative charges toward opposite ends of the crystal.

When a piezoelectric ceramic is subjected to an electric field, it undergoes a mechanical deformation known as the converse piezoelectric effect. This process causes the material to change its dimensions, a phenomenon resulting from the relative displacement of ions, rotation of dipoles, and redistribution of electrons within the crystal lattice.1234

In this state, the ceramic experiences a strain that is proportional to the applied electric field. Unlike electrostriction—a property of all dielectrics where deformation direction remains unchanged regardless of field polarity—the converse piezoelectric effect is characterized by a reversal in the direction of deformation when the electric field is reversed.32

While the dimensional change from a static electric field is typically small, it can be significantly enhanced by applying an alternating electric field that matches the material's natural mechanical resonance frequency. This capability is fundamental to the operation of various piezoelectric devices, including transducers for sound generation, ultrasonic equipment, and precision positioners.34