Domain Structures In Ferroelectric Materials Research Articles

Micro-electromechanical system-based cryogenic and heating in situ transmission electron microscopy for investigating phase transitions and domain evolution in single-crystal BaTiO3

Investigating phase transitions between ferroelectric states is crucial for understanding the nucleation, dynamics, and kinetics of domains, both before and after transformation. Here, we assess all phase transitions and domain evolutions in single-crystal BaTiO3 by implementing microelectromechanical systems (MEMS)-based in situ cryogenic (cryo-) and heating transmission electron microscopy (TEM) by continuously varying sample temperatures from -175 °C to 200 °C. Every possible phase-cubic, tetragonal, orthorhombic, and rhombohedral - was identified. An ultra-stable imaging condition was achieved with a mean drift speed of 1.52 nm/min, providing unique opportunities for atomic resolution in situ scanning TEM with a wide temperature range. Furthermore, domain nucleation and evolution across phase transitions were investigated using complementary dielectric measurements, optical microscopy, and a phenomenological model. This study underscores the effectiveness and utility of MEMS-based in situ cryo-/heating TEM in revealing phase transitions and domain structures in ferroelectric materials.

Strain Engineering of Domain Coexistence in Epitaxial Lead-Titanite Thin Films

Phase and domain structures in ferroelectric materials play a vital role in determining their dielectric and piezoelectric properties. Ferroelectric thin films with coexisting multiple domains or phases often have fascinating high sensitivity and ultrahigh physical properties. However, the control of the coexisting multiple domains is still challenging, thus necessitating the theoretical prediction. Here, we studied the phase coexistence and the domain morphology of PbTiO3 epitaxial films by using a Landau–Devonshire phenomenological model and canonic statistical method. Results show that PbTiO3 films can exist in multiple domain structures that can be diversified by the substrates with different misfit strains. Experimental results for PbTiO3 epitaxial films on different substrates are in good accordance with the theoretical prediction, which shows an alternative way for further manipulation of the ferroelectric domain structures.

Study on the Crystal and Domain Structures in Ferroelectric Materials during a Waste Heat Recovery Operation from Temporal Temperature Variation

Study on the Crystal and Domain Structures in Ferroelectric Materials during a Waste Heat Recovery Operation from Temporal Temperature Variation

The effective point charge of probe tip in piezoresponse force microscopy

Abrasions of the probe apexes always happen during piezoresponse force microscopy (PFM) experiments, resulting in variation of distribution of the electroelastic field in piezoelectric materials, which finally influences the spatial resolution of PFM. In this paper, we find the effective point charges coupled with the piezoelectric coefficients for three probe models including the modified point charge model, the sphere-plane model, and the disk-plane model, through the fully-coupled electromechanical method. It is proved that the wear of the probe apex induces spreading of electroelastic field from the contact area to the surrounding area, and the electroelastic fields computed using the coupled method are much more localized than that computed by the decoupled method. The piezoresponses underneath the probe apexes have no correlation with the geometries of the probes, yet strongly depend on the choices of calculation methods. This analysis paves new ways for studies of the piezoresponses in complicated domain structures in ferroelectric materials.

Flexoelectricity, strain gradients, and singularities in ferroelectric nanostructures

The effect of flexoelectricity on the formation and evolution of domain structures in ferroelectric materials is developed by integrating strain gradient theory into a finite element phase field model. Length scales associated with elastic strain gradients and the corresponding polarization gradient across a domain wall are integrated into the time-dependent Ginzburg–Landau theory and numerical simulated. Theoretical relations of a shear strain gradient along an electrode/dielectric interface are first solved and verified numerically using the finite element model. A singularity in the strain gradient–induced polarization is shown to occur as the elastic strain gradient length scale approaches a flexoelectric length scale. The theory and finite element modeling is then extended to quantify strain gradient electromechanics near 180° and 90° tetragonal phase domain structures. It is shown that the strain gradient length scale [Formula: see text] strongly influences changes in strain across the domain walls but has a negligible effect on the polarization. Strain gradient effects become negligible when [Formula: see text], where [Formula: see text] is the polarization domain wall length scale.

Phase field simulation of domain structures in ferroelectric materials within the context of inhomogeneity evolution

A phase field model for simulating the domain structures in ferroelectric materials is proposed. It takes mechanical and electric fields into account, thus allowing for switching processes due to mechanical and/or electrical loads. The central idea of the model is to take the spontaneous polarisation as an order parameter and to provide an evolution law for this parameter. The concept of evolving inhomogeneities (configuratioanl forces) can be used in this context, as the Spatial distribution of the spontaneous polarisation describes the inhomogeneity of the system. The evolution is found to be in agreement with the second law of thermodynamics and to resemble the (classical) Ginzburg-Landau equation. Numerical simulations show the features of the model and the interaction of domain structures with defects.

IMAGING AND CONTROL OF DOMAIN STRUCTURES IN FERROELECTRIC THIN FILMS VIA SCANNING FORCE MICROSCOPY

▪ Abstract Scanning force microscopy (SFM) is becoming a powerful technique with great potential both for imaging and for control of domain structures in ferroelectric materials at the nanometer scale. Application of SFM to visualization of domain structures in ferroelectric thin films is described. Imaging methods of ferroelectric domains are based on the detection of surface charges in the noncontact mode of SFM and on the measurement of the piezoelectric response of a ferroelectric film to an external field applied by the tip in the SFM contact mode. This latter mode can be used for nondestructive evaluation of local ferroelectric and piezoelectric properties and for manipulation of domains of less than 50 nm in diameter. The effect of the film thickness and crystallinity on the imaging resolution is discussed. Scanning force microscopy is shown to be a technique well suited for nanoscale investigation of switching processes and electrical degradation effects in ferroelectric thin films.

Studies of herringbone domain structures in lead titanate by electron back-scattering patterns

A new approach for studying domain structures in ferroelectric materials using electron back-scattering patterns (EBSP) is described. The herringbone-type domain structures in lead titanate single crystals were examined in detail. Three different EBS patterns, representing three possible polarization directions in the tetragonal phase, were obtained. Detailed analyses for identifying the major zone axes of the EBS patterns were correlated with the results from X-ray powder diffraction. Comparing the results from X-ray analysis and EBSP, the differences in the measurements of the interzonal angles were observed to be less than 1 degree. A simple rule for identifying domain structures from EBS patterns was obtained. EBSP provides quick but comparable structural information on domains compared with that from other advanced methods, such as TEM.