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Title: Emergent Low-Symmetry Phases and Large Property Enhancements in Ferroelectric KNbO 3 Bulk Crystals [Emergent Low-Symmetry Phases with Large Property Enhancement in Ferroelectric KNbO 3 Bulk Crystals]

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 KNbO 3 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 β‰ˆ0.017%, 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. In conclusion, this discovery reveals a potential new route to local engineering of significant property enhancements and conductivity through symmetry lowering in ferroelectric crystals.
 [1] ;  [1] ;  [2] ;  [3] ;  [3] ;  [1] ;  [1] ;  [4] ;  [3] ;  [5] ;  [1]
  1. Pennsylvania State Univ., University Park, PA (United States)
  2. Queen's Univ. Belfast, Northern Ireland (United Kingdom)
  3. Univ. of Texas at Austin, Austin, TX (United States)
  4. Argonne National Lab. (ANL), Argonne, IL (United States)
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357; DMR-1420620; DMR-1210588; DMR-1649490
Accepted Manuscript
Journal Name:
Advanced Materials
Additional Journal Information:
Journal Volume: 29; Journal Issue: 31; Journal ID: ISSN 0935-9648
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22); National Science Foundation (NSF)
Country of Publication:
United States
36 MATERIALS SCIENCE; conducting domain walls; ferroelectrics; low-symmetry phases; thermotropic phase boundaries
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1375060