ferroelektrisk

Ferroelectric materials are a class of dielectric materials that possess a spontaneous electric polarization that can be reversed or reoriented by an external electric field. This spontaneous polarization is a key characteristic that distinguishes them from other dielectric materials. The polarization arises from the alignment of electric dipoles within the crystal structure of the material. These dipoles are permanent and exist even in the absence of an external electric field.

The phenomenon of ferroelectricity is closely related to the concept of a ferroelectric phase transition. At a certain temperature, known as the Curie temperature, a material can transition from a paraelectric phase, where it lacks spontaneous polarization, to a ferroelectric phase, where it exhibits this property. Above the Curie temperature, the thermal vibrations are strong enough to overcome the forces aligning the dipoles, leading to random orientation and no net polarization. Below the Curie temperature, these forces dominate, resulting in the formation of aligned domains of spontaneous polarization.

The reorientability of the spontaneous polarization by an external electric field is what makes ferroelectric materials technologically significant. When an electric field is applied, the polarization within these domains can align with the field, leading to a net change in the material's polarization. This property allows for their use in a variety of electronic devices.

Applications of ferroelectric materials include non-volatile memory devices (like ferroelectric RAM or FeRAM), where the polarization state can be used to store binary data, and in actuators and sensors, where the electric field-induced strain or change in capacitance can be exploited. Other uses include pyroelectric detectors and frequency doublers. The study and development of ferroelectric materials continue to be an active area of research, seeking to improve their performance and discover new applications.