Multi-Disciplinary Materials Research Center, Frontier Institute of Science and Technology, and State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, Xi'an 710049, China.
National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, 305-0047, Ibaraki, Japan.
Phys Rev Lett. 2019 Sep 27;123(13):137601. doi: 10.1103/PhysRevLett.123.137601.
In ferroelectric and relaxor-ferroelectric materials, piezoelectric and dielectric properties are significantly enhanced at the morphotropic phase boundary (MPB), a boundary between different ferroelectric phases with different macroscopic symmetries. By contrast, in relaxor systems, such an MPB does not exist because relaxors of different compositions possess the same macroscopic symmetry. Here, we report the existence of a morphotropic relaxor boundary (MRB) in the single phase relaxor region of a K_{0.5}Na_{0.5}NbO_{3}-xBaTiO_{3} system, which is a composition-induced boundary between two relaxors with different local polar symmetries (tetragonal versus rhombohedral) but with the same macroscopic cubic symmetry. At the MRB the electrostrain increases by ∼3 times and the permittivity increases by ∼1.5 times over a wide temperature range of more than 100 K, as compared with off-MRB compositions. Our Letter demonstrates that the MRB may become an effective mechanism to enhance the dielectric and electrostrictive properties of relaxors.
在铁电体和弛豫铁电体材料中，在形态相变边界（MPB）处，压电和介电性能显著增强，这是不同具有不同宏观对称性的铁电相之间的边界。相比之下，在弛豫体系统中，由于不同组成的弛豫体具有相同的宏观对称性，因此不存在这样的 MPB。在这里，我们报告了在 K_{0.5}Na_{0.5}NbO_{3}-xBaTiO_{3} 体系的单相弛豫体区域中存在形态弛豫边界（MRB），这是两种具有不同局部极对称性（四方相对于菱方）但具有相同宏观立方对称性的弛豫体之间的组成诱导边界。在 MRB 处，电致伸缩应变在超过 100 K 的宽温度范围内增加了约 3 倍，介电常数增加了约 1.5 倍，与非-MRB 组成相比。我们的信件表明，MRB 可能成为增强弛豫体的介电和电致伸缩性能的有效机制。
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