Flexoelectric Poling of Functionally Graded Ferroelectric Materials

Abstract

Flexoelectricity is a phenomenon that can yield an electromechanical coupling in all dielectric materials, whereas piezoelectricity presents itself in specially treated (electrically poled) ferroelectric materials. The present study explores the possibility of achieving electrical poling in a material, purely by mechanical means, by virtue of flexoelectricity and thereby harnessing the potential of coexistence of the two phenomena. A theoretical investigation on a functionally graded ferroelectric material sample of square shape with barium titanate and polyvinylidene fluoride as its constituents is conducted in this direction using isogeometric analysis based computational framework. Applied mechanical load on the material results in varying magnitude of electric field inside the material, which in some fraction of the material reaches a magnitude sufficient enough to yield a permanent poling. Simulation results suggest that it is possible to achieve poling of up to 75% of the material volume. This partially poled material is later considered for its contribution in the total electromechanical coupling of the material. The combination of piezoelectric and flexoelectric effects is found to enhance the equivalent piezoelectric coefficient in converse electromechanical (by up to 90%) coupling while a detrimental effect is observed in direct equivalent piezoelectric coefficient (by up to 89%) due to this combination.

Flexoelectricity and surface effects on coupled electromechanical responses of graphene reinforced functionally graded nanocomposites: A unified size-dependent semi-analytical framework

“…Here the FGM system with a regular shaped (square) geometry is considered for analysis because it exhibits a more prominent flexoelectric effect due to the large strain gradient and can reduce the geometry dependency requirement of flexoelectricity (Sharma et al, 2021). In this paper, both flexoelectric and surface effects are considered.…”

“…Schematically, this can be expressed by the following relation: 𝑃 𝑖 ≈ d ijk ε jk + μ ijkl dir ε jk,l ; where μ ijkl dir and d ijk are direct flexoelectric (non-zero for all-dielectric materials) and piezoelectric constant (zero for non-piezoelectric materials), respectively (Chandratre and Sharma, 2012;Shu et al, 2019). Sharma et al (2021) reported the substantial enrichment in resultant coupling in the presence of flexoelectricity and piezoelectricity both in an electrically poled material sample. Besides the piezoelectric and flexoelectric effects, the surface effect is a size-dependent property that has a significant impact on the elastic response of structural building block elements.…”

Extended Isogeometric Analysis of Cracked Piezoelectric Materials in the Presence of Flexoelectricity

“…[ 9 ] So it is essential to incorporate flexoelectricity while designing micro and nano‐level piezoelectric devices. [ 21 ]…”

“…IGA, capable of modeling gradients, was applied to capture flexoelectricity in many works. [ 21,44–48 ] Yvonnet et al. [ 49 ] used Argyris elements in their study, which provides C 1 continuity to the displacement field.…”

Universal converse flexoelectricity in dielectric materials via varying electric field direction

“…For this purpose, cantilever-shaped energy harvesters and sensors, due to the presence of nonuniform strain in bending, have been vastly investigated in the past [22][23][24][25][26][27][28][29][30][31][32][33] Variable mechanical characteristics can result in varying strain distribution within the domain. A few studies have suggested the use of special composite materials to achieve variation in mechanical properties and thereby a strain gradient [34][35][36][37][38][39]. This method eliminates the need for special designs and dimensions of the devices to be employed, however, it requires an additional effort at manufacturing stage for compositional variation.…”