Elastic anomalies associated with domain switching in BaTiO3 single crystals under in situ electrical cycling

Abstract

The elastic response of BaTiO3 single crystals during electric field cycling at room temperature has been studied using in-situ Resonant Ultrasound Spectroscopy (RUS), which allows monitoring of both the elastic and anelastic changes caused by ferroelectric polarization switching. We find that the first ferroelectric switching of a virgin single crystal is dominated by ferroelastic 90° switching. In subsequent ferroelectric switching, ferroelastic switching is reduced by domain pinning and by the predominance of 180° ferroelectric domains, as confirmed by polarized light microscopy. RUS under in-situ electric field therefore demonstrates to be an effective technique for the investigation of electromechanical coupling in ferroelectrics.The process of polarization switching in ferroelectrics is generally not homogeneous and involves nucleation and growth of domains [1,2]. In prototypical tetragonal ferroelectrics, such as BaTiO3 at room temperature, two kinds of ferroelectric domains can nucleate [3]: 180° domains with polarizations antiparallel to each other, which minimize depolarization fields, and 90° domains with polarizations orthogonal to each other, which minimize strain via the formation of twins. During electrical poling, local strains are generated when 90° domains switch, but not when 180° domains switch. Limiting the mobility of domain walls by introducing specific point defects and domain engineering has proven an effective strategy to enhance piezoelectricity in BaTiO3 [4,5]. Large strains are desirable, e.g., to achieve giant magnetoelectric effects in multiferroic composites [6][7][8][9][10], and polarization switching without domain propagation is preferred for ferroelectric memory devices [11,12]. Separately, domain wall pinning and domain jamming may cause fatigue effects in ferroelectrics, hampering polarization switching upon repeated voltage cycling, ultimately limiting the performance of devices [13,14]. Understanding the role of domain structure on ferroelectric switching is thus of high technological relevance for the optimization

Beyond Substrates: Strain Engineering of Ferroelectric Membranes

“…Calculations show that the energy to create 90° domain boundaries is significantly lower than that of their 180° counterparts, [ 63 ] making it more favorable to realize the polarization reversal via two successive ferroelastic switching steps with creation of 90° domain walls, as observed experimentally in single crystals. [ 64 ] In epitaxial films, however, substrate clamping prevents the formation and propagation of these 90° domain walls during switching due to the large elastic energy cost. The removal of this constraint in the membranes—which are only weakly bonded to the silicon substrate—likely permits the local strains generated by 90° domain walls to be readily accommodated thus facilitating a lower‐energy switching process.…”

Giant caloric effects enhanced by the helix polarization at the 180° domain wall in tetragonal BaTiO3

“…The BTO keeps the 180° domain structure, and a slight movement of the domain wall can be detected when the electric field is smaller than 50 kV cm −1 , as shown in figure 1S iop.org/JPhysCM/31/495702/mmedia). Experimentally, it is reported that the 180° domain wall in the BTO crystals would move at a low electric field which is smaller than that predicted in this work [34]. It is mean that the small electric field should be chosen during the study of the influence of 180° domain wall on the electrocaloric effect in experimental.…”

Optical studies of ferroelectric and ferroelastic domain walls

“…Optical microscopy is a simple non-contact method ideal to observe in situ the response of ferroelastic domain walls to temperature [44][45][46][47][48], electric field [48][49][50][51][52][53][54][55][56][57][58][59][60][61] or stress [62,63]. In transmission, the use of crossed-polarizers, combined with a spatial resolution of the order of a half wavelength of light, produces high-contrast images of the domain structure.…”