Electrostrictive material

Electrostrictive materials are materials that exhibit a quadratic relationship between mechanical stress and the square of the electric polari2ation (14,15). Electrostriction can occur in any material. Whenever an electric field is appHed, the induced charges attract each other, thus, causing a compressive force. This attraction is independent of the sign of the electric field and can be approximated by... 

The strain j Hes along the axis of the electric field, E, or most often along the axis of the induced polari2ation, P. The electrostrictive coefficients for the electric field and polari2ation are M and respectively. Electrostriction is a small effect. In contrast to pie2oeIectric materials, electrostrictive materials... 

Typical electrostrictive materials include such compounds as lead manganese niobate lead titanate (PMN PT) and lead lanthanium 2irconate titanate (PLZT). Electrostriction is a fourth-rank tensor property observed in both centric and acentric insulators (14,15). 

Uchiko K., Piezo/Electrostrictive Materials, Morikita Publishing Co. Ltd., Tokyo, 1986. 

Magnetostrictive materials are analogs of electrostrictive materials that change shape when exposed to a magnetic field. The phenom-... 

This indicates that, if a biasing field Eh is applied to an electrostrictive material, there will be a direct proportionality between changes in strain and small changes in field (Eh 5E). 

Electrostrictive materials offer important advantages over piezoelectric ceramics in actuator applications. They do not contain domains (of the usual ferroelectric type), and so return to their original dimensions immediately a field is reduced to zero, and they do not age. Figure 6.24(a) shows the strain-electric field characteristic for a PLZT (7/62/38) piezoelectric and Fig. 6.24(b) the absence of significant hysteresis in a PMN (0.9Pb(Mg1/3Nb2/303-0.1 PbTi03) electrostrictive ceramic. 

A specific type of electrostrictive material with large electrostrictive coupling coefficients, and important for applications that require high... 

Fig. 15 Approximate performance limits of various mechanical driving principles used in alternators. Generally, higher frequency means lower work done per unit of pump mass. The dependence roughly follows the lines of constant specific power. A useful exception are the modem high-performance electrostrictive materials...

Relaxor-type electrostrictive materials, such as those from the lead magnesium niobate-lead titanate, Pb(Mgp 3Nb2/3)03-PbTi03 (or PMN-PT), solid solution are highly suitable for actuator applications. This relaxor ferroelectric also exhibits an induced piezoelectric effect. That is, the electromechanical coupling factor kt varies with the applied DC bias field. As the DC bias field increases, the coupling increases and saturates. Since this behavior is reproducible, these materials can be applied as ultrasonic transducers which are tunable by the bias field [12]. 

The most popular smart materials are piezoelectric materials, magnetostric-tive materials, shape-memory alloys, electrorheological fluids, electrostrictive materials, and optical fibers. Magnetostrictives, electrostrictives, shape-memory alloys, and electrorheological fluids are used as actuators optical fibers are used primarily as sensors (see Shape Memory Polymers)... 

Piezoelectric and electrostrictive materials are materials having the abihty to convert electric energy into mechanical energy. The effect is called piezoelectric if the generated surface charge density is linearly proportional to the... 

Electrostriction can generate mechanical deformation that is independent of the polarity of the electric field. It exists in almost all materials but is usually too weak for any practical use. However, it can be very large in electrostrictive materials, such as lead magnesium niobate (PMN) systems [11]. The nonlinearity often works to the advantage in such systems since it can produce tunable functional properties. As the effect is nonre-versible, electrostrictive materials are better for actuator applications. Unlike the piezoelectric effect, electrostriction can even exist in systems with center symmetry. Electrostrictive materials become piezoelectric under a dc bias field. 

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