期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 141, 期 35, 页码 13987-13994出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.9b07188
关键词
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资金
- National Natural Science Foundation of China (NSFC) [51722208]
- Key Technologies Research and Development Program of Sichuan Province [2018JY0007]
- Ministry of Education, Singapore, under its Tier 2 Grant [MOE2017-T2-1-129]
Owing to growing environmental concerns, the development of lead-free piezoelectrics with comparable performance to the benchmark Pb(Zr,Ti)O-3 (PZT) becomes of great urgency. However, a further enhancement of lead-free piezoelectrics based on existing strategies has reached a bottleneck. Here we achieve a slush polar state with multiphase coexistence in lead-free potassium-sodium niobate (KNN) piezoceramics, which shows a novel relaxor behavior, i.e., frequency dispersion at the transition between different ferroelectric phases. It is very different from the conventional relaxor behavior which occurs at the paraelectric-ferroelectric phase transition. We obtain an ultrahigh piezoelectric coefficient (d(33)) of 650 +/- 20 pC/N, the largest value of nontextured KNN-based ceramics, outperforming that of the commercialized PZT-5H. Atomic-resolution polarization mapping by Z-contrast imaging from different orientations reveals the entire material to comprise polar nanoregions with multiphase coexistence, which is again very different from conventional ferroelectric relaxors which have polar domains within a nonpolar matrix. Theoretical simulations validate the significantly decreased energy barrier and polarization anisotropy, which is facilitated by the high-density domain boundaries with easy polarization rotation bridging the multiphase-coexisting nanodomains. This work demonstrates a new strategy for designing lead-free piezoelectrics with further enhanced performance, which should also be applicable to other functional materials requiring a slush (flexible) state with respect to external stimulus.
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