UNIVERSITY PARK, Pa. — For years, researchers believed that the smaller the domain size in a ferroelectric crystal, the greater the piezoelectric properties of the material. However, recent findings by Penn State researchers have raised questions about this standard rule.
Ferroelectric materials possess spontaneous electric dipole moments that can be reversibly flipped by applying an electric field. Domains are areas in the ferroelectric crystal that have the dipole moments aligned in the same direction. Piezoelectricity is a material property where the crystal generates electrical charge under an applied mechanical force. This capability enables piezoelectrics to be used in electronics, sensors and actuators.
"So many devices in our daily life utilize the ability of a material to convert electrical signals to mechanical signals and vice versa,” said Bo Wang, postdoctoral scholar in materials science and engineering. “In most of these applications, the piezoelectric material plays a key role. And the most advanced piezoelectric materials are the ferroelectric materials.”
At a microscopic scale, ferroelectric materials consist of many domains, and these domains range in size from a few nanometers to as much as millimeters. Each domain consists of uniform or nearly uniform distribution of dipole moments, which occur when there is a separation of charge. The regions between adjacent domains are known as domain walls.