Emergent Low‐Symmetry Phases and Large Property Enhancements in Ferroelectric KNbO3 Bulk Crystals |
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| Authors: | Tom T. A. Lummen J. Leung Amit Kumar X. Wu Y. Ren Brian K. VanLeeuwen Ryan C. Haislmaier Martin Holt Keji Lai Sergei V. Kalinin Venkatraman Gopalan |
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| Affiliation: | 1. Department of Materials Science and Engineering, Pennsylvania State University, University Park, PA, USA;2. School of Mathematics and Physics, Queen's University Belfast, University Road, Belfast, Northern Ireland, UK;3. Department of Physics, University of Texas at Austin, Austin, TX, USA;4. Center for Nanoscale Materials, Argonne National Laboratory, Argonne, IL, USA;5. Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN, USA |
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| Abstract: | The design of new or enhanced functionality in materials is traditionally viewed as requiring the discovery of new chemical compositions through synthesis. Large property enhancements may however also be hidden within already well‐known materials, when their structural symmetry is deviated from equilibrium through a small local strain or field. Here, the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3 is reported. This phase is found to coexist with the nominal orthorhombic phase at room temperature, and is both induced by and stabilized with local strains generated by a network of ferroelectric domain walls. While the local microstructural shear strain involved is only ≈0.017%, the concurrent symmetry reduction results in an optical second harmonic generation response that is over 550% higher at room temperature. Moreover, the meandering walls of the low‐symmetry domains also exhibit enhanced electrical conductivity on the order of 1 S m?1. This discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals. |
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| Keywords: | conducting domain walls ferroelectrics low‐symmetry phases thermotropic phase boundaries |
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