Fu Zhengqian, Chen Xuefeng, Nie Henchang, Liu Yanyu, Hong Jiawang, Hu Tengfei, Yu Ziyi, Li Zhenqin, Zhang Linlin, Yao Heliang, Xia Yuanhua, Gao Zhipeng, An Zheyi, Zhang Nan, Cao Fei, Cai Henghui, Zeng Chaobin, Wang Genshui, Dong Xianlin, Xu Fangfang
State Key Laboratory of High Performance Ceramics and Superfine Microstructures & Key Lab of Inorganic Functional Materials and Devices, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, China.
School of Aerospace Engineering, Beijing Institute of Technology, Beijing, China.
Nat Commun. 2022 Mar 16;13(1):1390. doi: 10.1038/s41467-022-29079-w.
Phase boundary provides a fertile ground for exploring emergent phenomena and understanding order parameters couplings in condensed-matter physics. In Pb(ZrTi)O, there are two types of composition-dependent phase boundary with both technological and scientific importance, i.e. morphotropic phase boundary (MPB) separating polar regimes into different symmetry and ferroelectric/antiferroelectric (FE/AFE) phase boundary dividing polar and antipolar dipole configurations. In contrast with extensive studies on MPB, FE/AFE phase boundary is far less explored. Here, we apply atomic-scale imaging and Rietveld refinement to directly demonstrate the intermediate phase at FE/AFE phase boundary exhibits a rare multipolar Pb-cations ordering, i.e. coexistence of antipolar or polar displacement, which manifests itself in both periodically gradient lattice spacing and anomalous initial hysteresis loop. In-situ electron/neutron diffraction reveals that the same parent intermediate phase can transform into either FE or AFE state depending on suppression of antipolar or polar displacement, coupling with the evolution of long-/short-range oxygen octahedra tilts. First-principle calculations further show that the transition between AFE and FE phase can occur in a low-energy pathway via the intermediate phase. These findings enrich the structural understanding of FE/AFE phase boundary in perovskite oxides.
相界为探索凝聚态物理中的涌现现象和理解序参量耦合提供了丰富的研究领域。在Pb(ZrTi)O中，存在两种与成分相关且具有技术和科学重要性的相界，即把极性区域分隔成不同对称性的准同型相界（MPB）以及划分极性和反极性偶极构型的铁电/反铁电（FE/AFE）相界。与对MPB的广泛研究相比，FE/AFE相界的研究要少得多。在此，我们应用原子尺度成像和Rietveld精修来直接证明FE/AFE相界处的中间相呈现出罕见的多极Pb阳离子有序排列，即反极性或极性位移的共存，这在周期性梯度晶格间距和异常的初始磁滞回线中均有体现。原位电子/中子衍射表明，同一母体中间相可根据反极性或极性位移的抑制情况以及长/短程氧八面体倾斜的演变而转变为FE态或AFE态。第一性原理计算进一步表明，AFE相和FE相之间的转变可以通过中间相以低能量路径发生。这些发现丰富了对钙钛矿氧化物中FE/AFE相界的结构理解。
