Ren Xiaobing
Materials Physics Group, National Institute for Materials Science, Tsukuba, 305-0047, Ibaraki, Japan.
Nat Mater. 2004 Feb;3(2):91-4. doi: 10.1038/nmat1051. Epub 2004 Jan 11.
Ferroelectric crystals are characterized by their asymmetric or polar structures. In an electric field, ions undergo asymmetric displacement and result in a small change in crystal dimension, which is proportional to the applied field. Such electric-field-induced strain (or piezoelectricity) has found extensive applications in actuators and sensors. However, the effect is generally very small and thus limits its usefulness. Here I show that with a different mechanism, an aged BaTiO(3) single crystal can generate a large recoverable nonlinear strain of 0.75% at a low field of 200 V mm(-1). At the same field this value is about 40 times higher than piezoelectric Pb(Zr, Ti)O(3) (PZT) ceramics and more than 10 times higher than the high-strain Pb(Zn(1/3)Nb(2/3))O(3)-PbTiO(3) (PZN-PT) single crystals. This large electro-strain stems from an unusual reversible domain switching (most importantly the switching of non-180 degrees domains) in which the restoring force is provided by a general symmetry-conforming property of point defects. This mechanism provides a general method to achieve large electro-strain effect in a wide range of ferroelectric systems and the effect may lead to novel applications in ultra-large stroke and nonlinear actuators.
铁电晶体的特征在于其不对称或极性结构。在电场中，离子发生不对称位移，导致晶体尺寸发生微小变化，该变化与施加的电场成正比。这种电场诱导应变（或压电性）已在致动器和传感器中得到广泛应用。然而，这种效应通常非常小，因此限制了其用途。在此我表明，通过一种不同的机制，一块老化的钛酸钡（BaTiO₃）单晶在200 V/mm的低电场下可产生0.75%的大的可恢复非线性应变。在相同电场下，该值比压电锆钛酸铅（Pb(Zr,Ti)O₃，PZT）陶瓷高约40倍，比高应变的铌锌酸铅 - 钛酸铅（Pb(Zn₁/₃Nb₂/₃)O₃ - PbTiO₃，PZN - PT）单晶高10倍以上。这种大的电致应变源于一种不寻常的可逆畴翻转（最重要的是非180度畴的翻转），其中恢复力由点缺陷的一般对称顺应特性提供。这种机制提供了一种在广泛的铁电系统中实现大电致应变效应的通用方法，并且该效应可能会在超大行程和非线性致动器中带来新的应用。
