ferroelektroisissa

Ferroelectricity is a phenomenon observed in certain dielectric materials that exhibit a spontaneous electric polarization which can be reversed by applying an external electric field. This spontaneous polarization is analogous to ferromagnetism, where materials possess a spontaneous magnetic moment. The term "ferroelectric" was coined by Edwin C. Saw in 1945, drawing a parallel to the already established term "ferromagnetic".

A key characteristic of ferroelectric materials is the presence of a ferroelectric hysteresis loop, which plots the electric polarization (P) as a function of the applied electric field (E). This loop demonstrates that the polarization does not change linearly with the electric field. When an electric field is applied, the electric dipoles within the material align, leading to a net polarization. Upon removal of the field, some residual polarization, known as remanent polarization, remains. To reduce this polarization to zero, a coercive field must be applied in the opposite direction. Reversing the direction of the applied field further can then reverse the spontaneous polarization, completing the loop.

Ferroelectric materials typically possess a crystal structure that is non-centrosymmetric in their polarized state. Above a certain critical temperature, known as the Curie temperature (Tc), the material loses its ferroelectric properties and becomes paraelectric, where the polarization is induced solely by an external electric field and vanishes upon its removal. Examples of common ferroelectric materials include barium titanate (BaTiO3), lead zirconate titanate (PZT), and Rochelle salt. These materials find applications in various electronic devices, such as non-volatile memory (FeRAM), sensors, actuators, and ceramic capacitors.