Origin of the enhanced flexoelectricity of relaxor ferroelectrics

Abstract

We have measured the bending-induced polarization of Pb(Mg 1/3 Nb 2/3 )O 3 -PbTiO 3 single crystals with compositions at the relaxor-ferroelectric phase boundary. The crystals display very large flexoelectricity, with flexocoupling coefficients an order of magnitude bigger than the theoretical upper limit set by the theories of Kogan and Tagantsev. This enhancement persists in the paraphrase up to a temperature T* that coincides with the start of elastic softening in the crystals. Analysis of the temperature dependence and cross-correlation between flexoelectric, dielectric and elastic properties indicates that the large bendinginduced polarization of relaxor ferroelectrics is not caused by intrinsically giant flexoelectricity, but by the reorientation of polar nanotwins that become ferroelastically active below T*.

Large Flexoelectric Anisotropy in Paraelectric Barium Titanate

“…In contrast, Bersuker's theoretical analysis concludes instead that the large flexoelectric response is due to a flexoelectrically-induced alignment of precursor polarization that exists in the paraelectric phase of BTO [18]. In this scenario, BTO would behave similarly to relaxor ferroelectrics [19]. In this article we report a thorough experimental investigation on the magnitude and origin of the enhanced flexoelectricity in BTO single crystals.…”

Revisiting pyramid compression to quantify flexoelectricity: A three-dimensional simulation study

“…Common setups to induce strain gradients in simple geometries include bending of thin films [8][9][10] and compression of truncated pyramids or cones 11,12 . It has been found that flexoelectric coefficients are particularly large in materials with high dielectric constants, such as ferroelectrics 9,11,[13][14][15] . However, the magnitude of these coefficients greatly exceeds theoretical estimates 1, 16,17 .…”

Frequency dispersion of flexoelectricity in PMN-PT single crystal

“…Herein, the polar nano domain rotation polarization should be dominated to the flexoelectricity in PMN-PT single crystal. 29 As schematically shown in Fig. 4, at free state, the PNRs are randomly distributed in the crystal so that no net polarization can be observed.…”

“…The transverse flexoelectric coefficient was calculated to be as high as 100 µC/m at 12 Hz, which is comparable with that of some perovskite ceramics. 5, [12][13][14]29 The error bar of each measurement data in Fig. 2 originates from the small deviation of the collected charge under strain gradient.…”

“…Previous pioneering studies by Catalan et al have explicitly investigated the correlation between PNRs and flexoelectricity in other composition of PMN-PT single crystal. 29 Their result suggested that PNRs would be realigned and render to an extrinsic enhancement of flexoelectricity, which is proved by the cross correlation between the flexoelectric coefficients and elastic modulus during the phase transition. In this paper, we will further confirm the interpaly of PNRs and flexoelectricity by frequency characterization.…”