030070094 Buğra Çetinkaya 8th Week Definitions

1) Ferroelectricity (Material Property)

Previous Answer
Ferroelectric phase transtition discovered in Li-substiuated ZnO ceramics in 1996. Because of the easy fabrication of good-quality thin films on Si, sapphire and glass substrates, ZnO is one promising material for ferroelectric integrated devices and optoelectronic devices. The replacement of host Zn atoms by substitutional Li atoms, which was confirmed by X-ray structural analysis, play ana important role for the appearance of ferroelectricity. The mechanism of this novel ferroelectric phase transition has not been well understood yet.
(V. Stefan ,Ferroelectrics Vol.1 , pg:96)

New/Better Answer

Ferroelectricity is a spontaneous electric polarization of a material. Ferroelectric materials may exhibit a spontaneous dipole moment, the direction of which can be switched between equivalent states by the application of an external electric field. The term ferroelectricity is related to the concept of ferromagnetism, which has to do with the creation of a magnetic moment. Ferroelectrics are a subgroup of pyroelectrics.

Placing a ferroelectric material between two conductive plates creates a ferroelectric capacitor. Ferroelectric capacitors exhibit nonlinear properties and usually have very high dielectric constants. The fact that the internal electric dipoles can be forced to change their direction by the application of an external voltage gives rise to hysteresis in the "polarization versus voltage” property of the capacitor. In this case, polarization is defined as the total charge stored on the plates of the capacitor divided by the area of the plates. Hysteresis means memory and ferroelectric capacitors are used to make ferroelectric random access memory (RAM) for computers and radio frequency identification (RFID) cards.

(Jiri George Drobny, Polymers for Electricity and Electronics: Materials, Properties, and Applications, p. 22)