How does an applied electric field change the sizes of ferroelectric domains?

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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 an external electric field is applied to a ferroelectric material, the boundaries between adjacent domains shift. This movement allows domains that are already aligned with the direction of the applied field to grow in size at the expense of those that are out of alignment.1

This process results in a large net polarization within the material. While a material may initially consist of a multitude of randomly oriented domains—leading to an overall cancellation of polarization—the application of a strong electric field forces these domains to orient predominantly in one direction. This mechanism is fundamental to the material's high susceptibility to electric polarization, which directly influences its dielectric constant and capacity to store electric charge.12