Lv Xiang, Zhang Junwei, Liu Yao, Li Fei, Zhang Xi-Xiang, Wu Jiagang
Department of Materials Science, Sichuan University, Chengdu 610065, China.
Division of Physical Science and Engineering, King Abdullah University of Science and Technology, Thuwal 23955-6900, Kingdom of Saudi Arabia.
ACS Appl Mater Interfaces. 2020 Sep 2;12(35):39455-39461. doi: 10.1021/acsami.0c12424. Epub 2020 Aug 18.
Although the pronounced piezoelectricity was obtained in (K, Na)NbO piezoceramics with the phase boundary engineering (PBE), the physical mechanisms remain pending. Here, we revealed for the first time how PBE influences the piezoelectric properties through synergetic contributions. Cryogenic experiments confirm that PBE constructs a phase coexistence, consisting of rhombohedral (R), orthorhombic (O), and tetragonal (T) phases, with a structural softening, by which a high piezoelectric coefficient of 555 pC/N and the enhanced temperature stability of strain are achieved. The phenomenological theory and transmission electron microscopy demonstrate that the superior hinges on the flattened Gibbs free energy and the abundant nanodomains (10-80 nm), which induce the enhanced permittivity and the coexisting single domain and multidomain zones, respectively. In particular, we disclosed a trade-off relationship between ferroelectric domains and polar nanoregions (PNRs) and found the "double-edged sword" role of PNRs in the piezoelectricity enhancement. Therefore, this work helps understand the physical mechanisms of the piezoelectricity enhancement, benefiting the future research of lead-free piezoceramics.
尽管通过相界工程（PBE）在（K，Na）NbO压电陶瓷中获得了显著的压电性，但其物理机制仍不明确。在此，我们首次揭示了PBE如何通过协同作用影响压电性能。低温实验证实，PBE构建了一种由菱面体（R）、正交（O）和四方（T）相组成的相共存结构，并伴随着结构软化，由此实现了555 pC/N的高压电系数以及应变温度稳定性的增强。唯象理论和透射电子显微镜表明，其优异性能取决于扁平化的吉布斯自由能和丰富的纳米畴（10 - 80纳米），它们分别导致了介电常数的增强以及单畴和多畴区域的共存。特别是，我们揭示了铁电畴与极性纳米区域（PNRs）之间的权衡关系，并发现了PNRs在增强压电性方面的“双刃剑”作用。因此，这项工作有助于理解压电性增强的物理机制，有利于未来无铅压电陶瓷的研究。
