Dielectric electrostriction

The dielectric constants of amino acid solutions are very high. Thek ionic dipolar structures confer special vibrational spectra (Raman, k), as well as characteristic properties (specific volumes, specific heats, electrostriction) (34). 

Crystals with one of the ten polar point-group symmetries (Ci, C2, Cs, C2V, C4, C4V, C3, C3v, C(, Cgv) are called polar crystals. They display spontaneous polarization and form a family of ferroelectric materials. The main properties of ferroelectric materials include relatively high dielectric permittivity, ferroelectric-paraelectric phase transition that occurs at a certain temperature called the Curie temperature, piezoelectric effect, pyroelectric effect, nonlinear optic property - the ability to multiply frequencies, ferroelectric hysteresis loop, and electrostrictive, electro-optic and other properties [16, 388],... 

Pelrine, R., Kombluh, R., and Joseph, J.P., Electrostriction of pol3mier dielectrics with compliant electrodes as a means of actuation, J. Sensors Actuators, A Phy., 64, 77, 1998. 

Fig. 2.3 A schematic representation of the hydration layer near a small ion (left) and a large ion (right), showing the region where the water is dielectrically saturated (with a low relative permittivity e ), hence electrostricted (squeezed) and immobilized. The thickness of this layer, Ar, depends reciprocally on the size of the ion.

It must be noted that the above consideration for Case (A) assumes that the material is elastically heterogeneous but homogeneous in its dielectric property. If we assume heterogeneity in the electrostriction constant, CJC changes with strain, keeping //(//2 — ) constant, and hence another possibility of piezoelectricity may be introduced however, we will not take this complication into account in the following. 

Electrostriction Effect of Polymers Exhibiting Dielectric Relaxation... 

In this section we consider electrostriction in a polymer exhibiting dielectric relaxation. We assume for simplicity a single relaxation process ... 

Fig. 25. Ratio of electrostriction constant to dielectric constant of roll-drawn poly(vinylidene fluoride) film (draw-ratio = 2.3) plotted against angle 0 between elongational strain and draw-axis. Drawn after Nakamura and Wada [J. Polymer Sci. A-2,9,161 (1971)] by permission of John Wiley Sons, Inc.

Fig. 28. Piezoelectric stress constant obtained from inverse piezoelectric effect and electrostriction constant of drawn and polarized poly(vinylidene fluoride) film plotted against temperature. Draw ratio = 7. Polarized at 90° C under the field of 400 kV/ctn for 3 hours. Frequency of applied voltage = 37.5 Hz. (Oshiki and Fukada, 1971) Broken line represents dielectric constant at 21.5 Hz for roll-drawn poly (vinylidene fluoride) film (Peterlin and Eiweil, 1969)...

Converse piezoelectricity is a specific kind of a more general phenomenon known as electrostriction. Electrostriction is the deformation of a material exposed to an electrical field. Nearly all dielectrics... 

In conclusion the contribution to the dielectric response given by the third order susceptibility has different sources with opposite signs. Molecular simulations on ions in solution show that both dielectric saturation and electrostriction effects are presumably present and that for ions with a high charge density electric saturation predominates. This suggestion is in agreement with the general consensus that dielectric saturation is the first element to consider in the description of nonlinearities. 

We also quote the proposal, made by Luo and Tucker [19], of a model using a dielectric function with dependence of the dielectric constant on the electric field acting on the given position, used for supercritical liquids, in which the solvent density is particularly sensitive to the local value of external electric fields. Emphasis is given in this model to electrostriction effects. 

Shrout, T.R. et al. (1987) Grain size dependence of dielectric and electrostriction (properties) of Pb(Mgi/3Nb2/3)03 -based ceramics, Ferroelectrics, 76, 479-87. 

Electrostriction — The change of shape of an insulating material (dielectric) under the effect of an electric field. The deformation is proportional to the square of the polarization. 

A, the estimated dielectric constant is 63.5 from Eq. (35), and EA = 8.3 x 103 esu-cm 2. The estimated electrostrictional molar volume change (0.144 x 18) is 0.26 cm3-mole 1. This is in good agreement with the estimates of Desnoyers, Verrall, and Conway 8 for this field strength. The effect of the term (-Pu,iA.AA/2).dV on the interaction energy of interaction up to dielectric saturation is small, but not negligible. 

From tensor algebra, the tensor property relating two associated tensor quantities, of rank / and rank g, is of rank (/-b g). Hence, the physical property connecting /, and aj is the third-rank tensor known as the piezoelectric effect, and it contains 3 = 27 piezoelectric strain coefficients, dyk. The piezoelectric coefficients are products of electrostriction constants, the electric polarization, and components of the dielectric tensor. 

Additional difficulties beyond that of dielectric saturation already mentioned (page 527) have to do with the enormous electrostrictive pressures in the neighborhoods of ions. These can amount to some 10 to 10 atm and lead to serious changes in the properties of the solvent (unpublished work by the author). Note that these lead to an increase in dielectric constant due to compression of solvent and tend to cancel the effects of saturation. For some detailed discussion, see paper by H. S. Frank, J. Chem, Phys.j 23, 2023 (1966). 

Permittivity variations in a strong electric field non-linear and saturation behaviour progress of e gperimental methods molecular behaviour and various theoretical models molecular correlations complete dielectric saturation electrostriction and electrocaloric effect. 

Electrostriction. By the thermodynamics of dielectrics, the thermodynamic potential (Helmholtz function 10 of a didectric in a uniform external fidd Eo at constant pressure and temperature is ... 

In the general case, electrostriction is not isotropic even in isotropic dielectrics a field-induced anisotropy of electrostriction appears and is perceptible also in measurements of the static" and optical" Kerr effects. This anisotropy of electrostriction is particularly apparent if the field acting on the dielectric is strong, such as the intense electromagnetic field of a light wave, in which case the time-dynamics of the electrostrictive effect have to be studied s arately." ... 

---