The evolution of ferroelectric domain structures inside a single grain embedded in a polycrystalline BaTiO3 ceramic was investigated under temperature and electric field using the three-dimensional X-ray diffraction (3D-XRD) method. The orientation of domains within the grain was studied during the phase transformation from the cubic to tetragonal crystal structure. The peak widths broadened from 0.10 ± 0.01• to 0.29 ± 0.08• along the azimuthal direction during cooling. Four individual tetragonal domain structures were developed from the cubic grain. A twinning model based on {101} habit planes is discussed. While the twinning model predicts 89.47• misorientation between 90• domains and 1.049• misorientation between domain variants, the measured misorientations neither support the twinning model nor are the domain structures mutually orthogonal. The average misorientation of the domain structures at room temperature with respect to the cubic grain was about 0.3• . Upon application of an electric field, the volume fractions of the domain structures changed systematically favoring growth of domain structures with small polarization angle with respect to applied field direction. No rotation of domain structures was observed upon application of an electric field which is consistent with domain boundary migration.
The twinning structure of the orthorhombic α martensite phase in alpha + beta Ti-3.5Al-4.5Mo (wt%) titanium alloy was studied using X-ray diffraction and transmission electron microscopy by water quenching from below transus temperatures. While water quenching from 910 • C induced the formation of {110} • twins, quenching from 840 • C formed the α martensite with {111} • type I twins. The effect of the principle strains on the twinning structure was discussed. As compared to the previous studies, the principle strains play an important role in the formation of the twinning type.
The evolution of ferroelectric domains inside a single grain of a polycrystalline BaTiO 3 ceramic was investigated under quasistatic heating by using polychromatic scanning X-ray microdiffraction (µSXRD). Four domain orientations were observed, three of which exhibited a classic ~90° ferroelastic relationship. The fourth domain orientation was found to be crystallographically related to one of the other orientations by a rotation of either 180.47° or 0.47°. While heating the polycrystalline BaTiO 3 from room temperature to above the Curie temperature (125°C), all four ferroelectric domain orientations rotated towards a paraelectric cubic orientation which was found to be at an intermediate orientation relative to the four domain orientations. The crystallographic relationships of the domains with respect to paraelectric phase were explained using a domain structure model by Nepochatenko.
Strain and texture evolution (domain switching) of polycrystalline, ferroelectric BaTiO 3 was investigated in four-point bending geometry. Lattice strains were measured by in situ synchrotron X-ray diffraction to address problems related to modeling the constitutive behavior of highly asymmetric ferroelectrics. The hkl-dependent strain measured by X-ray diffraction was found to be smaller relative to both bulk strain measured by conventional, contact-based techniques and elastically computed strain, and reasons for this inconsistency are discussed. A self-consistent model with capabilities of quantifying domain switching and estimating hkl-dependent strain is applied to allow a direct comparison with diffraction data.
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