Dislocation-density changes upon poling of polycrystallineBaTiO3

Abstract

We report evidence for a significant increase of bulk dislocation density upon poling of polycrystalline BaTiO 3. The synchrotron high-resolution x-ray-diffraction measurements yield a dislocation density on the order of 10 9 /cm 2 and an associated strain-energy increase of about 20 kJ/m 3. This implies that the application of an external poling field generates defects in the structure and increases the internal stress. Possible consequences in both bulk and thin-film applications include accelerated aging and microcracking. ͓S0163-1829͑99͒06005-1͔

Highly localized strain fields due to planar defects in epitaxial SrBi2Nb2O9 thin films

“…2 In recent years, several authors evidenced that this regular stacking along the ͓001͔ direction can be disrupted so as to form stacking faults, [3][4][5][6][7][8] i.e., the number of BO 6 octahedra sheets can locally differ from its average value m = 2. 14 Moreover, in addition to structural defects, inhomogeneous strain fields related to defects [15][16][17][18] and homogeneous strain fields ͑mostly related to the lattice mismatch in the case of thin films͒ 19,20 are known to seriously affect the properties of ferroelectric materials as well. As the ferroelectric properties of Aurivillius phases arise from the perovskite layer, 9,10 stacking faults are critically important to the ferroelectric properties.…”

On the polarization dynamics in the presence of flexoelectricity and morphotropic phase boundary in ferroelectrics

“…The broadening of diffraction lines in polycrystalline BaTiO 3 indicates large microstructural changes, especially along the direction of polarization and polarizing field , ( 2 ) where is the permittivity tensor, E is the applied external ac electric field, and is the dielectric susceptibility (independent of the field strength). According to the data of [32], the inhomogeneous deformation along the polarization direction is of the same order of magnitude as the deformation caused by electrostriction, which indicates a significant growth in the dislocation density.…”

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Effect of strain on tunability in Ba0.60Sr0.40TiO3 thin films on Pt–Si substrates

“…30,31 Again, these defects will have bigger effect at high electric fields where the electromechanical deformation is large. The theory deviates from experimental data at high fields and increases monotonically.…”

“…The theory deviates from experimental data at high fields and increases monotonically. 30,31 The relation between the grain size and the physical properties needs to be addressed theoretically, a task that is inherently difficult even for "passive" materials. We attribute this to grain boundaries and other defects that are present in the films.…”