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Defect‐Driven Structural Distortions at the Surface of Relaxor Ferroelectrics
Author(s) -
Kong Scarlet,
Kumar Nitish,
Checchia Stefano,
Cazorla Claudio,
Daniels John
Publication year - 2019
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201900344
Subject(s) - materials science , piezoelectricity , characterization (materials science) , ferroelectricity , stress (linguistics) , diffraction , perovskite (structure) , ceramic , condensed matter physics , polar , surface stress , dielectric , nanotechnology , composite material , optoelectronics , optics , surface energy , crystallography , linguistics , philosophy , physics , chemistry , astronomy
Relaxor‐ferroelectric materials find application in a broad range of technological devices, including ultrasonic imaging transducers, nanopositioning, and high‐performance capacitors. They generally exhibit occupationally disordered structures creating local polar fluctuations that are highly sensitive to applied electric or stress fields. The sensitivity of the material structure to external field and stress conditions also makes them likely to develop skin or surface phases that are unique from the bulk. Surface layers can adjust the material response and also lead to ambiguity in structural characterization. Here, using a combination of X‐ray diffraction methods, it is shown that a ≈20 µm skin structure commonly exists in the lead‐free relaxor‐ferroelectric ceramic (Na 1/2 Bi 1/2 )TiO 3 –BaTiO 3 . Using experiments and density functional theory calculations, it is shown that the combined action of oxygen vacancies providing internal chemical pressure and the surface plane stress state dictates the stability and structure of the skin layer. This work can be extended to all perovskite relaxor ferroelectrics and provides new insights into the origin of skin layers in these materials. The opportunity exists to further enhance the functionality of these materials through engineering of surface structures using the methods outlined here.