Switching of morphotropic phase boundary and large strain response in lead-free ternary (Bi0.5Na0.5)TiO3-(K0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3 system
Switching of morphotropic phase boundary and large strain response in lead-free ternary (Bi0.5Na0.5)TiO3-(K0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3 system
复制标题
无铅三元(Bi0.5Na0.5)TiO3-(K0.5Bi0.5)TiO3-(K0.5Na0.5)NbO3体系中同形相界的切换和大应变响应
DOI：
10.1063/1.4795511
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发表时间：
2013-03-21
影响因子：
3.2
通讯作者：
Gao, Xingyu
中科院分区：
文献类型：
--
作者：
Hao, Jigong;Shen, Bo;Gao, Xingyu
本文报道了无铅三元（1 -y）[(1 -x)(Bi0.5Na0.5) TiO3-x (Bi0.5K0.5)TiO3]-y(K0.5Na0.5)NbO3 （BNT-BKT-KNN）体系的相图，并研究了相变相界（MPB）的开关特性。KNN的加入从本质上改变了体系的结构性质，使MPB从铁电方面体和铁电四方相之间的MPB(I)转变为铁电方面体和弛豫赝赝相之间的MPB（II）。当MPB(I)切换到MPB（II）时，与MPB(I)附近BNT-0.20BKT获得的150pC/N相似的d（33）的大压电响应几乎消失。相反，在MPB（II）附近，由于铁电弛豫转变温度TF-R下降到室温，电场诱导应变S显著跃升至0.32%-0.46% （S-max/E-max = 400-575 pm/V）。在本研究中，在x = 0.20, y = 0.01的BNT-BKT-KNN体系中，一个非常狭窄的区域出现了类似0.46%的巨大应变，该区域位于菱形(R)，四边形(T)和伪锥面（Pc）相的三临界三相点上。外加电场的原位高能x射线散射实验表明，MPB（II）材料的Pc结构存在初始电场致畸变，而具有单R相的材料则不存在初始电场致畸变，这说明由于MPB（II）材料的结构相对不稳定，在MPB（II）附近产生的大应变可能是电场致结构畸变引起的。我们相信，在伪三元体系中发现应变响应一致可导的成分线，应该有助于通过搜索mpb在其他基于bbnt的体系中设计高性能压电材料。(C) 2013年美国物理研究所。[http://dx.doi.org/10.1063/1.4795511]
In this work, we report the phase diagram of lead-free ternary (1 - y)[(1 - x)(Bi0.5Na0.5) TiO3-x (Bi0.5K0.5)TiO3]-y(K0.5Na0.5)NbO3 (BNT-BKT-KNN) system and study the switching characteristics of the morphotropic phase boundary (MPB). The addition of KNN intrinsically changes the structural nature of the system with the shift of MPB from MPB(I) between ferroelectric rhombohedral and ferroelectric tetragonal phases to MPB(II) between ferroelectric rhombohedral and relaxor pseudocubic phases. As the MPB(I) switches to MPB(II), large piezoelectric response with d(33) similar to 150pC/N that obtained for BNT-0.20BKT near MPB(I) almost disappears. Instead, a significant jump of electric-filed-induced strain S up to 0.32%-0.46% (S-max/E-max = 400-575 pm/V) is achieved near MPB(II) due to the shift of the ferroelectric-relaxor transition temperature TF-R down to room temperature. In this study, giant strain similar to 0.46% occurs in a very narrow region in the BNT-BKT-KNN system with x = 0.20, y = 0.01, which lies on an underlying tricritical triple point of a rhombohedral (R), tetragonal (T), and pseudocubic (Pc) phases. In-situ high-energy X-ray scattering experiments with external electric field reveal an initial electric-field-induced distortion from the Pc structure for the MPB(II) compositions, while those with single R phase shows no such distortion, which suggests that the large strain achieved near the MPB(II) is likely to be induced by the electric-field-induced structure distortion due to its relative instability structure. We believe that the discovery of a compositional line in the pseudo-ternary system, where the strain response is consistently derivable, should be useful for designing high-performance piezoelectric materials in other BNT-based systems by searching MPBs. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4795511]