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Encyclopedia > Ferroelectricity

In physics, the ferroelectric effect is an electrical phenomenon whereby certain 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 used in analogy to ferromagnetism, in which a material exhibits a permanent magnetic moment. Physics (Greek: (phúsis), nature and (phusiké), knowledge of nature) is the branch of science concerned with the fundamental laws of the universe. ... Electrical phenomena are commonplace and unusual events that can be observed which illuminate the principles of the physics of electricity and are explained by them. ... This article is about the electromagnetic phenomenon. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... A bar magnet. ...


There are two main types of ferroelectrics: displacive and order-disorder. The effect in barium titanate, a typical ferroelectric of the displacive type, is due to a polarization catastrophe, in which, if an ion is displaced from equilibrium slightly, the force from the local electric fields due to the ions in the crystal increase faster than the elastic-restoring forces. This leads to an asymmetrical shift in the equilibrium ion positions and hence to a permanent dipole moment. In an order-disorder ferroelectric, there is a dipole moment in each unit cell, but at high temperatures they are pointing in random directions. Upon lowering the temperature and going through the phase transition, the dipoles order, all pointing in the same direction within a domain. Barium titanate is an oxide of barium and titanium with the chemical formula BaTiO3. ... It has been suggested that optical field be merged into this article or section. ... In physics, a net force acting on a body causes that body to accelerate; that is, to change its velocity. ...


Another important ferroelectric material is lead zirconate titanate. Lead zirconium titanate (PZT, also Lead zirconate titanate) is a ceramic perovskite material that shows a marked piezoelectric effect - that is, it develops a voltage difference across two of its faces when compressed, and ferroelectric effect. ...


Ferroelectric crystals often show several transition temperatures and domain structure hysteresis, much as do ferromagnetic crystals. By analogy to magnetic core memory, this hysteresis can be used to store information in ferroelectric RAM, which has ferroelectric capacitors as memory cells. The nature of the phase transition in some ferroelectric crystals is still not well understood. Crystal (disambiguation) Insulin crystals A crystal is a solid in which the constituent atoms, molecules, or ions are packed in a regularly ordered, repeating pattern extending in all three spatial dimensions. ... Hysteresis is a property of systems (usually physical systems) that do not instantly follow the forces applied to them, but react slowly, or do not return completely to their original state: that is, systems whose states depend on their immediate history. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... A 16×16 cm area core memory plane of 128×128 bits, i. ... Ferroelectric RAM (FRAM or FeRAM) is a type of non-volatile computer memory, similar to EEPROM but based on electric field orientation and with near-unlimited number (exceeding 1010 for 5V devices and even more for 3. ... Ferroelectric capacitor is a capacitor used in digital electronics as a component of computer memory. ... In physics, a phase transition, (or phase change) is the transformation of a thermodynamic system from one phase to another. ...


Ferroelectrics often have very large dielectric constants, and thus are often used as the dielectric material in capacitors. They also often have unusually large nonlinear optical coefficients. The relative dielectric constant of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux. ... Capacitors: SMD ceramic at top left; SMD tantalum at bottom left; through-hole tantalum at top right; through-hole electrolytic at bottom right. ... Nonlinear optics is the branch of optics that describes the behaviour of light in nonlinear media, that is, media in which the polarization P responds nonlinearly to the electric field E of the light. ...


Older publications used the term electret for ferroelectric materials. Electret (formed of elektr- from electricity and -et from magnet) is material that has been permanently electrically charged (polarised). ...


The ferroelectric effect also finds use in liquid crystal physics by incorporation of a chiral dopant into an achiral smectic C matrix. These liquid crystals exhibit the Clark-Lagerwall effect[1] which effects a change in one bistable state to another upon switching of electric field direction. Schlieren texture of Liquid Crystal nematic phase Liquid crystals are substances that exhibit a phase of matter that has properties between those of a conventional liquid, and those of a solid crystal. ...

Contents

References

  1. ^ Noel A. Clark, Sven Torbjörn Lagerwall: Submicrosecond Bistable Electro-Optic Switching in Liquid Crystals, Appl. Phys. Lett. 36, 899 (1980)

Applied Physics Letters is a weekly peer-reviewed journal published by the American Institute of Physics devoted to the publication of new experimental and theoretical papers about applications of physics to science, engineering, and modern technology. ...

See also

Physics

Paraelectricity is a phenomene, or rather crystal phase, where electric dipoles are unaligned (i. ... Piezoelectricity is the ability of crystals, certain ceramic materials, (and to some degree, all materials) to generate a voltage in response to applied mechanical stress. ... Pyroelectricity is the ability of certain materials to generate an electrical potential when they are heated or cooled. ... Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ... Unsolved problems in physics: Is it possible to construct a practical electronic device that operates on the spin of the electron, rather than its charge? Spintronics (a neologism for spin-based electronics), also known as magnetoelectronics, is an emergent technology which exploits the quantum spin states of electrons as well... Fixed Partial Denture, or Bridge The word ceramic is derived from the Greek word κεραμικός (keramikos). ...

People

Oliver Heaviside (May 18, 1850 – February 3, 1925) was a self-taught English electrical engineer, mathematician, and physicist who adapted complex numbers to the study of electrical circuits, developed techniques for applying Laplace transforms to the solution of differential equations, reformulated Maxwells field equations in terms of electric and...

Lists

Electrical phenomena are commonplace and unusual events that can be observed which illuminate the principles of the physics of electricity and are explained by them. ... This page aims to list all Wikipedia articles that are related to physics. ... This is a list of communications, computers, electronic circuits, fiberoptics, microelectronics, medical electronics, reliablity, and semiconductors. ...

External links

  • A useful starter on ferroelectrics
  • [1]

  Results from FactBites:
 
Ferroelectric - definition of Ferroelectric in Encyclopedia (241 words)
In physics, the ferroelectric effect is an electrical phenomenon whereby certain ionic crystals may exhibit a spontaneous dipole moment.
The effect in barium titanate, a typical ferroelectric of the displacive type, is due to a polarization catastrophe, in which, if an ion is displaced from equilibrium slightly, the force from the local electric fields due to the ions in the crystal increase faster than the elastic restoring forces.
Ferroelectrics often have very large dielectric constants, and thus are often found in capacitors.
  More results at FactBites »

 
 

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