Beijing Advanced Innovation Center for Materials Genome Engineering, University of Science and Technology Beijing, 100083, Beijing, China.
Department of Physical Chemistry, University of Science and Technology Beijing, 100083, Beijing, China.
Nat Commun. 2023 Feb 23;14(1):1007. doi: 10.1038/s41467-023-36749-w.
Relaxor ferroelectrics are known for outstanding piezoelectric properties, finding a broad range of applications in advanced electromechanical devices. Decoding the origins of the enhanced properties, however, have long been complicated by the heterogeneous local structures. Here, we employ the advanced big-box refinement method by fitting neutron-, X-ray-based total scattering, and X-ray absorption spectrum simultaneously, to extract local atomic polar displacements and construct 3D polar configurations in the classical relaxor ferroelectric Pb(MgNb)O-PbTiO. Our results demonstrate that prevailing order-disorder character accompanied by the continuous rotation of local polar displacements commands the composition-driven global structure evolution. The omnidirectional local polar disordering appears as an indication of macroscopic relaxor characteristics. Combined with phase-field simulations, it demonstrates that the competing local polar order-disorder between different states with balanced local polar length and direction randomness leads to a flattening free-energy profile over a wide polar length, thus giving rise to high piezoelectricity. Our work clarifies that the critical structural feature required for high piezoelectricity is the competition states of local polar rather than relaxor.
弛豫铁电体以其出色的压电性能而闻名，在先进的机电设备中有着广泛的应用。然而，长期以来，由于局域结构的不均匀性，对增强性能的起源的解码一直很复杂。在这里，我们采用先进的大盒子精修方法，通过同时拟合中子、基于 X 射线的全散射和 X 射线吸收谱，提取局域原子极性位移并构建经典弛豫铁电 Pb(MgNb)O-PbTiO3 中的 3D 极性构型。我们的结果表明，普遍存在的有序-无序特征伴随着局部极性位移的连续旋转，控制着组成驱动的全局结构演化。各向同性的局部极性无序是宏观弛豫特征的表现。结合相场模拟，它表明不同状态之间局部极性的竞争有序-无序导致局部极性长度和方向随机性的平衡，从而在较宽的极性长度范围内导致自由能曲线变平，从而产生高的压电性。我们的工作表明，高压电性所必需的关键结构特征是局部极性的竞争状态，而不是弛豫。
