The Effect of Ultrafine Ferroelectric Material Grain Size on Energy Storage Density

Using molecular dynamics simulation, we conducted a study to investigate the relationship between the hysteresis loop, residual polarization, coercive field, and dielectric constant of barium titanate polycrystals under the influence of different electric fields, in relation to grain size. The smaller the grain size, the greater the electric field required for complete polarization domain reversal. As grain size increases, the non-linear correlation of the ferroelectric hysteresis loop strengthens, but it becomes challenging to achieve saturation polarization at low electric fields. Additionally, we observed the formation, migration, and annihilation of polarization vortex domains. These vortex domains initially appear near grain boundaries, then migrate into the interior of the grains, and eventually vanish. The speed of vortex domain movement is directly proportional to the energy density of the polycrystal. It's worth noting that energy efficiency decreases with the increase of grain size and electric field magnitude.