Electromechanical Response of Polycrystalline Barium Titanate Resolved at the Grain Scale

Abstract

Ferroic materials are critical components in many modern devices. Polycrystalline states of these materials dominate the market due to their cost effectiveness and ease of production. Studying the coupling of ferroic properties across grain boundaries and within clusters of grains is therefore critical for understanding bulk polycrystalline ferroic behavior. Here, three-dimensional X-ray diffraction is used to reconstruct a 3D grain map (grain orientations and neighborhoods) of a polycrystalline barium titanate sample and track the grain-scale non-180°ferro-electric domain switching strains of 139 individual grains in situ under an applied electric field. The map shows that each grain is located in a very unique local environment in terms of intergranular misorientations, leading to local strain heterogeneity in the as-processed state of the sample. While primarily dependent on the crystallographic orientation relative to the field directions, the response of individual grains is also heterogeneous. These unique experimental results are of critical importance both when building the starting conditions and considering the validity of grain-scale modeling efforts, and provide additional considerations in the design of novel ferroic materials. K E Y W O R D Sdomains, microstructure, polycrystalline materials, X-ray methods

Multistep stochastic mechanism of polarization reversal in rhombohedral ferroelectrics

“…In this respect, piezoresponse force microscopy (PFM) and transmission electron microscopy (TEM) disclosed clustering during polarization reversal which ranges from a few [40] to 10 2 -10 3 grains [41,42] in polycrystalline thin films. In contrast to the latter results, in bulk ceramics the grain-resolved three-dimensional X-ray diffraction revealed a collective dynamics at a scale of about 10-20 grains [43][44][45] that roughly corresponds to the next neighbors. The study of polarization and electric field correlations by means of the self-consistent mesoscopic switching model (SMS) [46][47][48], revealed that the electric fieldmediated correlations in bulk ceramics have a typical scale of a grain size.…”

Stochastic multistep polarization switching in ferroelectrics

“…1(b), because the possible polarizations of grains are specified by their crystallographic orientations, which are randomly distributed. Additionally, in bulk polycrystals, domains can interact across grain boundaries leading to longer length-scale coupling of domain dynamics [30,31,59]. The c-axis directional distribution should be taken into account and the simplified formula for ∆𝑆 𝑚𝑎𝑥 has to be generalized to ∆S max_real = (Q 12 − Q 11 )P s 2 < (sin 2 θ) > 𝑚𝑎𝑥 (26) where < sin 2 θ > 𝑚𝑎𝑥 defines a maximum possible value for (P 𝑥 2 + 𝑃 𝑦 2 )/P s 2 compatible with the tetragonal symmetry of grains when polarization tries to avoid z-direction.…”

“…Thus, the switching of different regions in a ceramic can still be considered as statistically independent with regard to electrical interactions. Correlations in polarization switching, observed between tens of grains in bulk samples [30,31] or up to thousand grains in films [32][33][34], seem to be related to the elastic rather than to the electric interactions. Therefore, the original definition of different regions has to be extended to take elastic interactions into account.…”

Grain interaction mechanisms leading to intragranular orientation spread in tensile deformed bulk grains of interstitial-free steel

“…For completeness applications of 3DXRD to minerals (Borthwick et al, 2012;Hall and Wright, 2015;Sørensen et al, 2012a), deep earth science (Nisr et al, 2014(Nisr et al, , 2012Rosa et al, 2015), nuclear materials (Brown et al, 2014;X. Zhang et al, 2015), superalloys (Sedmák et al, 2016) and ferroelectrics Majkut et al, 2016;Varlioglu et al, 2010) should also be mentioned.…”