electromagnetism In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interacti ...

, electrostriction is a property of all electrical non- conductor or

dielectrics In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the materia ...

. Electrostriction causes these materials to change their shape under the application of an

electric field An electric field (sometimes called E-field) is a field (physics), physical field that surrounds electrically charged particles such as electrons. In classical electromagnetism, the electric field of a single charge (or group of charges) descri ...

. It is the dual property to

magnetostriction Magnetostriction is a property of magnetic materials that causes them to change their shape or dimensions during the process of magnetization. The variation of materials' magnetization due to the applied magnetic field changes the magnetostrictive ...

Explanation

Electrostriction is a property of all dielectric materials, and is caused by displacement of

ion An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

s in the crystal lattice upon being exposed to an external electric field. The cause of electrostrictive is linked to anharmonic effects. Positive ions will be displaced in the direction of the field, while negative ions will be displaced in the opposite direction. This displacement will accumulate throughout the bulk material and result in an overall strain (elongation) in the direction of the field. The thickness will be reduced in the orthogonal directions characterized by

Poisson's ratio In materials science and solid mechanics, Poisson's ratio (symbol: ( nu)) is a measure of the Poisson effect, the deformation (expansion or contraction) of a material in directions perpendicular to the specific direction of loading. The value ...

. All insulating materials consisting of more than one type of atom will be ionic to some extent due to the difference of electronegativity of the atoms, and therefore exhibit electrostriction. The resulting strain (ratio of deformation to the original dimension) is proportional to the square of the polarization. Reversal of the electric field does not reverse the direction of the deformation. More formally, the electrostriction coefficient is a rank four

tensor In mathematics, a tensor is an algebraic object that describes a multilinear relationship between sets of algebraic objects associated with a vector space. Tensors may map between different objects such as vectors, scalars, and even other ...

(

Q_

), relating the rank two strain tensor (

\varepsilon_

) and the electric

polarization density In classical electromagnetism, polarization density (or electric polarization, or simply polarization) is the vector field that expresses the volumetric density of permanent or induced electric dipole moments in a dielectric material. When a die ...

vector (i.e. rank one tensor;

P_k

) :

\varepsilon_ = Q_P_k P_l.

The electrostrictive tensor satisfies :

Q_ = \frac\frac.

The related

piezoelectric effect Piezoelectricity (, ) is the electric charge that accumulates in certain solid materials—such as crystals, certain ceramics, and biological matter such as bone, DNA, and various proteins—in response to applied stress (mechanics), mechanical s ...

occurs only in a particular class of dielectrics. Electrostriction applies to all crystal symmetries, while the piezoelectric effect only applies to the 20 piezoelectric point groups. Piezoelectricity is a result of electrostrictive in ferroelectric materials. Electrostriction is a quadratic effect, unlike piezoelectricity, which is a

linear In mathematics, the term ''linear'' is used in two distinct senses for two different properties: * linearity of a '' function'' (or '' mapping''); * linearity of a '' polynomial''. An example of a linear function is the function defined by f(x) ...

effect.

Materials

Although all dielectrics exhibit some electrostriction, certain engineered ceramics, known as relaxor ferroelectrics, have extraordinarily high electrostrictive constants. The most commonly used are * lead magnesium niobate (PMN) * lead magnesium niobate-lead titanate (PMN-PT) * lead lanthanum zirconate titanate (PLZT)

Magnitude of effect

Electrostriction can produce a strain on the order of 0.1% for some materials. This occurs at a field strength of 2 million volts per meter (2 MV/m) for the material PMN-15. Electrostriction exists in all materials, but is generally negligible.

Applications

Sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances ( ranging), communicate with or detect objects o ...

projectors for submarines and surface vessels *

Actuator An actuator is a machine element, component of a machine that produces force, torque, or Displacement (geometry), displacement, when an electrical, Pneumatics, pneumatic or Hydraulic fluid, hydraulic input is supplied to it in a system (called an ...

s for small displacements * Sensors, provided a bias electric field or pre-stress is present.

Explanation

Materials

Magnitude of effect

Applications

See also

References

Further reading