Journal
JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS
Volume 142, Issue -, Pages -Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jmps.2020.104020
Keywords
Flexoelectric effect; Piezoresponse force microscopy; Mixed finite element method
Funding
- Key-Area Research and Development Program of Guangdong Province [2018B010109009]
- National Natural Science Foundation of China [11627801, 11632014]
- Shenzhen Science and Technology Innovation Committee [JCYJ20170818163902553]
- National Key R&D Program of China [2017YFE0119800, B18040]
- Chang Jiang Scholar Program
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Flexoelectricity refers to phenomena that polarization is coupled with strain gradient and stress is coupled with electric gradient. It occurs in all dielectrics, and becomes significant under a sharp conductive tip in piezoresponse force microscopy (PFM), under which large gradients in electromechanical field naturally arise. Here we analyze direct and converse flexoelectric effects under such a scanning probe, using mixed finite element method (FEM) developed under the phenomenological continuum framework. The FEM was first validated by analytic solutions for simple axially-symmetric tubes, and then applied to analyze two different modes of PFM experiments. It reveals that the flexoelectric effect accounts for less than 20% of the measured piezoresponse in a typical piezoelectric material, while mechanical switching via flexoelectricity is only possible for ferroelectric materials having upward polarization, with the switching zone confined to a small region near surface. These analyses explain a number of experimental observations well, and shed insight into complex electromechanical phenomenon under a sharp PFM tip. The theoretical and computational framework developed can also be applied to study flexoelectric effect in other structural configurations. (C) 2020 Elsevier Ltd. All rights reserved.
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