Large strain electrostrictive actuation in barium titanate

Abstract

Large strain electrostriction in single-crystal ferroelectric materials is investigated. The mode of electrostriction is based on a combined electromechanical loading used to induce cyclic, 90°domain switching. Experiments have been performed on crystals of barium titanate with constant compressive stress and oscillating electric-field input. Induced strains of more than 0.8% have been measured. Strains as large as 5% are predicted for other materials of the same class. The results demonstrate a possible avenue for obtaining large actuation strains in electromechanical devices. © 2000 American Institute of Physics. ͓S0003-6951͑00͒01137-2͔Ferroelectric ceramics are used in a variety of sensor and actuator applications. In particular, they are one of the basic building blocks of smart structures which have been successfully used for active damping and damage detection. The behavior of conventional materials is characterized by good high-frequency response and low hysteresis, but unfortunately, very small strains ͑limited to about 0.1%͒. A variety of methods have been developed for creating large displacement actuators by using monomorph or bimorph benders, functionally graded ceramics, and single crystals. Research on single-crystal ferroelectric materials for sensor and actuator applications have recently focused on exotic relaxorbased systems, formulated near the morphotropic phase boundary, that take advantage of phase transition to produce large actuation strains. 1 The current investigation focuses on the use of domain reorientation to generate a large actuation strain in a ferroelectric single crystal of a simple perovskite structure. Experiments have been performed on barium titanate (BaTiO 3 ), a common ferroelectric, generating strains of more than 0.8%.The current study is motivated by the theoretical work of Shu and Bhattacharya who developed a model of a ferroelectric single crystal using the setting of finite deformations. 2 They assume the existence of a crystal free-energy density W, which is dependent on the deformation gradient (F), polarization ( P), and temperature ( ). For a flat plate configuration with electrodes on two faces, the total energy G can be expressed in three terms consisting of the crystal freeenergy density, and external mechanical and electrical work:where T o is stress and E o is the applied electric field. For a material such as barium titanate, there exist six possible ground states with the polarization vector in one of the six pseudocubic ͗100͘ directions. These ground states correspond to multiple energy wells of W. When considering a compressive stress and electric field across the ferroelectric plate, minimization of the total energy results in a phase diagram describing the exchange of stability of the different directions of polarization in the stress-electric-field space.The analysis further suggests that there exists a low-energy path for switching from one polarization to another. Thus, domain polarization can be switched by electric field or applied stress. Fur...

Domain patterns, texture and macroscopic electro-mechanical behavior of ferroelectrics

“…It turns out that in this formula (3) above, one may replace W with a relaxed or mesoscale energy W which may be defined for each y by holding it constant in the formula (3). W is the effective energy density of the single crystal.…”

“…It begins with a classical and phenomenological Landau-Ginzburg-Devonshire type theory, shows that this theory reveals important aspects of domain patterns, and tries to systematically average their effect to larger scales. It reports on the work of Shu and Bhattacharya [2] and Burscu, Ravichandran and Bhattacharya [3] on single crystals and then summarizes the work of Li and Bhattacharya [4] on polycrystals. This line of research parallels recent work in the study of the shape-memory effect in martensitic materials [5][6][7][8], and magnetostriction in the recently developed ferromagnetic shape-memory alloys [9,10].…”

A Mesoscopic Electromechanical Theory of Ferroelectric Films and Ceramics

“…It has recently been recognized that it is possible to obtain large actuation strains in ferroelectric single crystals through polarization rotation [1,2], or by domain switching as a result of applied electric field and mechanical stress [3,4]. However, large strains cannot usually be obtained in a polycrystalline ferroelectrics due to the incompatibility between neighboring grains.…”

Phase switching at low field and large sustainable strain output in domain engineered ferroic crystals

“…A combined mechanical stress and electric field are used to induce 908 domain switching in FE tetragonal single crystal BaTiO 3 [14]. A complete switching of polarization direction by 908, i.e., from a-to c-domains will result in a large lattice strain of approximately 1% (c/a $ 1.01) at $3 MV m À1 .…”