Ferroelectricity

Ferro electricity (Qualitative)

Dielectric materials which possess electric polarization even in the absence of electric field (spontaneous polarization) are known as ferroelectric materials. They exhibit electrical hysteresis for the variation of polarization P with the applied electric field E analogous to the way ferromagnetic material exhibit magnetic hysteresis for variation of B with H.

Ferroelectric materials possess very high values of e_r of the order of 1000 to 10000. In ferroelectric materials the value of e_r changes with temperature according to the relation, e_r = C/T-T_C above T_C, where T_C is called Curie temperature. This is known as Curie-Wiess law of ferroelectrics. Rochelle salt, BaTiO₃ and PbTiO₃ are examples of ferroelectric materials. These materials are widely used in capacitors, electronic circuits and in memory devices.