Emergent low-symmetry phases and large property enhancements in Ferroelectric KNbO3 bulk crystals

Tom T. A. Lummen, J. Leung, Amit Kumar, X. Wu, Y. Ren, Brian K. Vanleeuwen, Ryan C. Haislmaier, Martin Holt, Keji Lai, Sergei Kalinin, Venkatraman Gopalan

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31 Citations (Scopus)
231 Downloads (Pure)

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 lowered from equilibrium through a small local strain or field. This work reports on the discovery of enhanced material properties associated with a new metastable phase of monoclinic symmetry within bulk KNbO3. This phase is found to co-exist 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 bulk ferroelectric crystals.
Original languageEnglish
Article number1700530
Pages (from-to)1
JournalAdvanced Materials
Volume29
Issue number31
Early online date19 Jun 2017
DOIs
Publication statusEarly online date - 19 Jun 2017

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