Ferroelectrische

Ferroelectric materials are substances that exhibit spontaneous electric polarization, which can be reversed by applying an external electric field. This switchable polarization leads to a characteristic hysteresis loop in polarization versus electric field and underpins many practical devices. Ferroelectricity is a property of certain crystalline materials, often with non-centrosymmetric structures, that retain a polarization state in the absence of an external field.

The ferroelectric state typically arises below a characteristic temperature called the Curie temperature, at which the material undergoes a phase transition from a paraelectric to a ferroelectric phase. Polarization results from displacements of ions within the crystal lattice and from the formation of domains, regions where polarization is uniformly oriented. The orientation of these domains can be changed by electric fields, influencing dielectric, piezoelectric, and electro-optic properties.

Common ferroelectric materials include perovskites such as barium titanate (BaTiO3) and lead zirconate titanate (Pb(Zr,Ti)O3, PZT). A defining feature is strong piezoelectric coupling, meaning these materials can efficiently convert between electrical and mechanical energy. All ferroelectrics are piezoelectric, though not all piezoelectrics are ferroelectric.

Applications span non-volatile memory (ferroelectric RAM), capacitors, actuators, sensors, and electro-optic devices. In addition to performance, environmental and health considerations have driven ongoing research into lead-free ferroelectrics and alternative materials. Ferroelectricity was first observed in Rochelle salt in the 1920s, and the field has since evolved to include a wide range of oxides and related compounds.