Polarization states and dielectric responses of elastically clamped ferroelectric nanocrystals

Azovtsev, Andrei V.; Pertsev, N. A.

doi:10.1063/1.4969048

Cited by 5 publications

(24 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For all we know, similar effects have not been observed previously in ferroelectric superlattices. And meanwhile, the same changes in the type of the phase transition were recordered in the calculation work on ferroelectric composites 21 .…”

Section: Resultsmentioning

confidence: 73%

Repolarization of Ferroelectric Superlattices BaZrO3/BaTiO3

Сидоркин

Nesterenko

Gagou

et al. 2019

Sci Rep

View full text Add to dashboard Cite

With the use of the modified Sawyer-Tower scheme and Merz technique, studies were conducted on the repolarization characteristics of ferroelectric (BaZrO3/BaTiO3) superlattices on monocrystalline MgO substrate. Studies of temperature changes in the dielectric hysteresis loops indicated a sufficiently smooth decrease in spontaneous polarization compared with homogeneous barium titanate near the phase transition temperature of the superlattice. Experimental studies of switched currents have shown that the switching processes in the synthesized superlattices are implemented in two stages: activation motion (“creep” mode) and non-activation motion (slip mode). The presence of the activation switching stage and the numerical estimates show that with high probability, the movement of domain boundaries accomplishes the processes of switching in the studied superlattice. The threshold field separating the stated stages decreases with increasing temperature up to the Curie point of the superlattice, similar to the coercive field. Detection of the non-strictly exponential dependence of the switching current on the reverse field strength in the activation stage was modulated by the dependence with the power-law exponent for the applied electric field. Both techniques indicate that the studied superlattices have a small internal displacement field directed from the superlattice to the substrate.

show abstract

Section: Resultsmentioning

confidence: 73%

Repolarization of Ferroelectric Superlattices BaZrO3/BaTiO3

Сидоркин

Nesterenko

Gagou

et al. 2019

Sci Rep

View full text Add to dashboard Cite

show abstract

“…For a homogeneously polarized ellipsoidal inclusion in a linear elastic medium, the equilibrium polarization state can be found via the minimization of a special thermodynamic potential G allowing for the mechanical inclusion-matrix interaction [6,8]. We shall consider only inclusions having the shape of ellipsoids of revolution (spheroids) with the symmetry axis x 3 parallel to the [0 0 1] crystallographic direction of the inclusion's prototypic cubic phase.…”

Section: Permittivities Of Strained Ferroelectric Nanocrystalsmentioning

confidence: 99%

“…In our calculations, the temperature dependence of the differential thermal strain ∆S T was approximated by a linear relation ∆S T = (β m − β p )(T − T 0 ), where β m and β p are mean thermal expansion coefficients of the matrix and the inclusion's prototypic cubic phase, respectively. The corrections Δα ij to the fourth-order thermodynamic coefficients, which are caused by elastic 3D clamping of inclusions by the matrix [8], were regarded as temperature-independent quantities.…”

Section: Permittivities Of Strained Ferroelectric Nanocrystalsmentioning

confidence: 99%

“…When the crystallite dimensions are much larger than the unit-cell size, the contribution to the total matrix effect, which is associated with short-range interfacial interactions, becomes less significant than the contribution of long-range mechanical and electric fields appearing inside the ferroelectric inclusion. The mechanical matrix effect, which involves the elastic three-dimensional (3D) clamping of ferroelectric inclusions and the generation of thermal stresses due to dissimilar thermal expansion of two contacting materials [5][6][7][8][9], should be especially important for ferroelectric nanocrystals surrounded by rigid dielectric matrices such as glasses. Such FE-DE nanocomposites have been fabricated in many laboratories by embedding ferroelectric substances into various porous dielectrics, including synthetic opals [10,11], silica glass [12,13], sodium borosilicate glass [14,15], and aluminum oxide [16].…”

Section: Introductionmentioning

confidence: 99%

“…For nanocrystals of perovskite ferroelectrics embedded into rigid glass media, thermodynamic theory predicts that the mechanical inclusion-matrix interaction shifts the temperature of paraelectric to ferroelectric phase transition, may change its order from first to second, and even qualitatively alters the evolution of ferroelectric states on cooling under certain conditions [8,9]. At a given temperature, the equilibrium polarization state of ferroelectric inclusion depends not only on the elastic stiffnesses of the surrounding medium, but also on the inclusion's shape.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Dielectric properties of ferroelectric nanocomposites: effects of thermal stresses and filler shape anisotropy

Nikitchenko

Azovtsev

Pertsev

2018

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Ferroelectric nanocomposites are intriguing nonhomogeneous materials, which may have unusual phase states and specific physical properties useful for practical applications. Here we theoretically describe dielectric properties of nanocomposites comprising single-domain ferroelectric nanocrystals embedded into a linear dielectric medium. First, small-signal intrinsic permittivities of spheroidal PbTiO and BaTiO crystallites surrounded by an isotropic matrix with linear elastic properties are calculated with the aid of a nonlinear thermodynamic theory. It is shown that thermal stresses caused by differences in thermal expansion between the inclusions and the matrix may strongly influence the intrinsic permittivities of ferroelectric nanocrystals. Second, macroscopic dielectric responses of ferroelectric-dielectric composites are evaluated in the Maxwell Garnett approximation. For effective permittivities of such composites, generalized relations are derived, which allow for both the shape and dielectric anisotropies of ferroelectric nanocrystals. Numerical calculations of the effective permittivities are performed for composites comprising PbTiO and BaTiO nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. For nanocomposites involving randomly oriented and similarly aligned spheroidal inclusions, temperature dependences of the effective permittivities are determined with the account of phase transitions occurring in strained ferroelectric nanocrystals and suppression of their dielectric responses due to the depolarizing-field effect created by low-permittivity matrix. Our theoretical calculations show that effective permittivities of composites comprising needle-like or disc-shaped ferroelectric inclusions could strongly exceed the permittivity of the matrix. Most importantly, we predict that BaTiO-KO-SiO composites with such inclusions should exhibit a broad dielectric peak around the room temperature, which is associated with shifted structural transitions in strained BaTiO nanocrystals. The presented theory provides guidelines for the development of ferroelectric nanocomposites with enhanced dielectric responses, which could be suitable for applications in supercapacitors and other advanced electronic devices.

show abstract

Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

Nikitchenko

Azovtsev

Pertsev

2017

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

Ferroelectric crystallites embedded into a dielectric matrix experience temperature-dependent elastic strains caused by differences in the thermal expansion of the crystallites and the matrix. Owing to the electrostriction, these lattice strains may affect polarization states of ferroelectric inclusions significantly, making them different from those of a stress-free bulk crystal. Here, using a nonlinear thermodynamic theory, we study the mechanical effect of elastic matrix on the phase states of embedded single-domain ferroelectric nanocrystals. Their equilibrium polarization states are determined by minimizing a special thermodynamic potential that describes the energetics of an ellipsoidal ferroelectric inclusion surrounded by a linear elastic medium. To demonstrate the stability ranges of such states for a given material combination, we construct a phase diagram, where the inclusion's shape anisotropy and temperature are used as two parameters. The 'shape-temperature' phase diagrams are calculated numerically for PbTiO and BaTiO nanocrystals embedded into representative dielectric matrices generating tensile (silica glass) or compressive (potassium silicate glass) thermal stresses inside ferroelectric inclusions. The developed phase maps demonstrate that the joint effect of thermal stresses and matrix-induced elastic clamping of ferroelectric inclusions gives rise to several important features in the polarization behavior of PbTiO and BaTiO nanocrystals. In particular, the Curie temperature displays a nonmonotonic variation with the ellipsoid's aspect ratio, being minimal for spherical inclusions. Furthermore, the diagrams show that the polarization orientation with respect to the ellipsoid's symmetry axis is controlled by the shape anisotropy and the sign of thermal stresses. Under certain conditions, the mechanical inclusion-matrix interaction qualitatively alters the evolution of ferroelectric states on cooling, inducing a structural transition in PbTiO nanocrystals and suppressing in BaTiO inclusions some transformations occurring in their bulk counterpart. The constructed phase maps open the possibility to calculate dielectric properties of strained PbTiO and BaTiO nanocrystals and ferroelectric nanocomposites comprising such crystallites.

show abstract

Polarization states and dielectric responses of elastically clamped ferroelectric nanocrystals

Cited by 5 publications

References 24 publications

Repolarization of Ferroelectric Superlattices BaZrO3/BaTiO3

Repolarization of Ferroelectric Superlattices BaZrO3/BaTiO3

Dielectric properties of ferroelectric nanocomposites: effects of thermal stresses and filler shape anisotropy

Phase diagrams of ferroelectric nanocrystals strained by an elastic matrix

Contact Info

Product

Resources

About