Role of Microstructures in the Dielectric Properties of PVDF-Based Nanocomposites Containing High-Permittivity Fillers for Energy Storage.

Polymer-based nanocomposites containing inorganic ferroelectric inclusions, typically ABO perovskites, have emerged as innovative dielectric materials for energy storage and electric insulation, potentially coupling the high breakdown strength (BDS) and easy processing of polymers with the enhancement of dielectric constant provided by the ferroelectric phase. In this paper, experimental data and three-dimensional finite element method (3D FEM) simulations were combined to shed some light on the effect of microstructures on the dielectric properties of poly(vinylidene fluoride) (PVDF)-BaTiO composites. The existence of particle aggregates or touching particles has a strong effect on the effective dielectric constant and determines an increase of the local field in the neck region of the ferroelectric phase with a detrimental effect on the BDS.

Influence of Ferroelectric Filler Size and Clustering on the Electrical Properties of (Ag-BaTiO)-PVDF Sub-Percolative Hybrid Composites.

The paper presents a study concerning the role of ferroelectric filler size and clustering in the dielectric properties of 20%BaTiO-80%PVDF and of 20% (2%Ag-98%BaTiO)-PVDF hybrid nanocomposites. By finite element calculations, it was shown that using fillers with ε > 10 does not provide a permittivity rise in the composites and the effective dielectric constant tends to saturate to specific values determined by the filler size and agglomeration degree. Irrespective of the ferroelectric filler sizes, the addition of metallic ultrafine nanoparticles (Ag) results in permittivity intensification and the effect is even stronger if the metallic nanoparticles are connected to a higher degree with the ferroelectric particles' surfaces.

Optimization of Processing Steps for Superior Functional Properties of (Ba, Ca)(Zr, Ti)O Ceramics.

Lead-free piezoelectric ceramics with nominal composition at morphotropic phase boundary BaCaTiZrO (BCTZ) prepared by different processing routes and sintered either by conventional solid-state reaction or by spark plasma sintering (SPS) techniques were comparatively investigated to observe the role of structural modifications and of microstructures on the dielectric, ferroelectric, piezoelectric and electrocaloric responses. The ceramics presented relative densities from 75% to 97% and showed variations in their phase composition as a result of variable mixing and different synthesis and sintering parameters providing local compositional heterogeneity. As result, all of the ceramics showed diffuse phase transition and ferroelectric switching responses, with parameters affected mostly by density ( between 3.

Mesoscale Models for Describing the Formation of Anisotropic Porosity and Strain-Stress Distributions during the Pressing Step in Electroceramics.

Porous ceramics are often produced by using pyrolisable additives to generate porosity during the sintering step. The examination of the experimental microstructures of the resulted porous ceramics revealed certain levels of anisotropy, even if the original soft additives used as pore forming agents were spherical. The paper shows that anisotropic porosity may result in ceramics when using equiaxed soft polymeric additives for generating porosity, due to the deformation of soft inclusions during the pressing step.

Increasing Permittivity and Mechanical Harvesting Response of PVDF-Based Flexible Composites by Using Ag Nanoparticles onto BaTiO Nanofillers.

The role of Ag addition on the structural, dielectric, and mechanical harvesting response of 20%(Ag - (1 - )BaTiO) - 80%PVDF ( = 0, 2, 5, 7 and 27 vol.%) flexible composites is investigated. The inorganic fillers were realized by precipitating fine (~3 nm) silver nanoparticles onto BaTiO nanoparticles (~60 nm average size).

Preparation and Functional Properties of BaTiO-BaGeO Ceramics.

The phase formation and functional properties (dielectric, ferroelectric switching, and tunability) in x BaGeO-( 1- x )BaTiO ceramics with compositions x = 0 , 0.01, 0.018, 0.

Ferroelectric order driven Eu photoluminescence in BaZrTiO perovskite.

The ability to tune and enhance the properties of luminescent materials is essential for enlarging their application potential. Recently, the modulation of the photoluminescence emission of lanthanide-doped ferroelectric perovskites by applying an electric field has been reported. Herein, we show that the ferroelectric order and, more generally the polar order, has a direct effect on the photoluminescence of Eu in the model BaZrTiO perovskite even in the absence of an external field.

Monte Carlo simulations for describing the ferroelectric-relaxor crossover in BaTiO₃-based solid solutions.

The properties induced by the M(4+) addition (M = Zr, Sn, Hf) in BaM(x)Ti(1-x)O(3) solid solutions have been described on the basis of a 2D Ising-like network and Monte Carlo calculations, in which BaMO(3) randomly distributed unit cells were considered as being non-ferroelectric. The polarization versus temperature dependences when increasing the M(4+) concentration (x) showed a continuous reduction of the remanent polarization and of the critical temperature corresponding to the ferroelectric-paraelectric transition and a modification from a first-order to a second-order phase transition with a broad temperature range for which the transition takes place, as commonly reported for relaxors. The model also describes the system's tendency to reduce the polar clusters' average size while increasing their stability in time at higher temperatures above the Curie range, when a ferroelectric-relaxor crossover is induced by increasing the substitution (x).