Flexoelectricity

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Flexoelectricity is a property of a dielectric material where there is coupling between electrical polarization and a strain gradient. Flexoelectricity is closely related to piezoelectricity, but while piezoelectricity refers to polarization due to uniform strain, flexoelectricity refers specifically to polarization due to strain that changes from point to point in the material. This nonuniform strain breaks centrosymmetry, meaning that unlike in piezoelectricity, flexoelectric effects occur in both centrosymmetric and asymmetric crystal structures. [1] Flexoelectricity is not the same as Ferroelasticity. Flexoelectricity plays a critical role in explaining many interesting electromechanical behaviors in hard crystalline materials and core mechanoelectric transduction phenomena in soft biomaterials. [2] Most excitingly, flexoelectricity is a size-dependent effect that becomes more significant in nanoscale systems, such as crack tips. [3]

Contents

In common useage flexoelectricity is the generation of polarization due to a strain gradient; inverse flexoectricity is when polarization, often due to an applied electric field, generates a strain gradient. Converse flexoelectricity is where a polarization gradient induces strain in a material. [4]

The electric polarization due to mechanical strain of in a dielectric is given by

where the first term corresponds to the direct piezoelectric effect and the second term corresponds to the flexoelectric polarization induced by the strain gradient.

Here, the flexoelectric coefficient, , is a fourth-rank polar tensor and is the coefficient corresponding to the direct piezoelectric effect.

See also

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References

  1. Pavlo Zubko, Gustau Catalan, and Alexander K. Tagantsev (2013). "Flexoelectric Effect in Solids". Annual Review of Materials Research . 43: 387–421. Bibcode:2013AnRMS..43..387Z. doi:10.1146/annurev-matsci-071312-121634. hdl: 10261/99362 .{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. Thanh D. Nguyen, Sheng Mao, Yao-Wen Yeh, Prashant K. Purohit, Michael C. McAlpine (2013). "Nanoscale Flexoelectricity". Adv. Mater. 25 (7): 946–974. doi:10.1002/adma.201203852. PMID   23293034.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  3. Hongguang Wang, Xijie Jiang, Yi Wang, Robert W. Stark, Peter A. van Aken, Jochen Mannhart, Hans Boschker (2020). "Direct observation of huge flexoelectric polarization around crack tips". Nano Lett. 20 (1): 88–94. doi:10.1021/acs.nanolett.9b03176. PMID   31851827.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  4. Abdollahi A, Domingo N, Arias I, Catalan G (2019). "Converse flexoelectricity yields large piezoresponse force microscopy signals in non-piezoelectric materials". Nature Communications. 10 (1): 1266. Bibcode:2019NatCo..10.1266A. doi: 10.1038/s41467-019-09266-y . PMC   6427004 . PMID   30894544.