Influence of Depolarizing Fields and Screening Effects on Phase Transitions in Ferroelectric Composites.

Boris Darinskii,Alexander Sidorkin,Nadezhda Popravko,Alexander Sigov

doi:10.3390/ma11010085

Boris Darinskii, Alexander Sidorkin + Show 2 more

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https://doi.org/10.3390/ma11010085

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Abstract

The temperature of the transition to the polar state in ferroelectric composites, representing spherical ferroelectric inclusions embedded in a dielectric matrix, under a depolarizing field effect is investigated. This temperature is determined both in the absence and presence of screening effects of the depolarizing field of the bound charges of spontaneous polarization at the inclusions surface. The absence case shows that the Curie point shift is determined by the ratio of the Curie constant of the ferroelectric inclusion to the permittivity of the matrix. Screening effects show that the transition temperature shift decreases through multiplying the value by a decreasing factor equal to the ratio of the screening length to the radius of the ferroelectric inclusion. Examples of the materials for the position of the Curie point on the temperature scale, largely determined by the tilting action of the depolarizing field and the compensating shielding effects, are given.

Highlights

The general increase in the requirements for functional opportunities of different devices has sharply increased the demands placed on their elemental base
The present work calculates depolarizing fields arising near the boundaries of a spherical ferroelectric inclusion in an isotropic dielectric environment and evaluates the effect of these fields, and screening effects on the Curie point in the composites
Nanocrystalline cellulose with ferroelectric sodium nitrite particles and silica with triglycine sulfate particles were considered to be representative samples of these materials

Summary

Introduction

The general increase in the requirements for functional opportunities of different devices has sharply increased the demands placed on their elemental base. Natural materials no longer satisfy the growing technological and operational requirements, due to the limited range of operating parameters, randomness of their characteristics, and the absence of possibilities for changing functional parameters. Ferroelectric nanocomposites are one such object, whose properties are extremely sensitive to size effects caused by the increased role of surface or boundary effects. The special sensitivity of these materials is caused by phase transitions, which increase the compliance of the structure to various impacts. Identification of linkages between various characteristics and the structure of these materials will allow researchers to find new ways of controlling their parameters, which is essential for practical materials science. The changes in the dielectric constant, including the dispersion of the permittivity of ferroelectric composites, their piezoelectric and pyroelectric properties, have been considered in several pieces of research [4–14]

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