Microwave Dielectric Properties of CCTO/PVA Composites

M P F Graça,K D A Sabóia,F Amaral,L C Costa

doi:10.1155/2018/6067519

Abstract

The CaCu3Ti4O12 (CCTO) ceramic powder was inserted in the polyvinyl alcohol (PVA) polymeric matrix, with an increasing weight fraction of the filler, to form a flexible and high dielectric constant composite at the GHz region. The structural characterization of the samples was performed using X-ray diffraction and scanning electron microscopy (SEM). The complex permittivity was calculated by the small perturbation theory using two resonant cavities (2.7 GHz and 5.0 GHz). Several classical models (Maxwell Garnett, Lichtenecker, effective medium theory (EMT), and Yamada) were used to fit the real part of the complex permittivity of the composite as a function of the weight fraction of CCTO powder inserted in the PVA matrix. The best predictions for the dielectric behavior of these samples were obtained with the EMT and Yamada models.

Highlights

Materials with excellent dielectric properties, such as a highdielectric constant, low dissipation factor, and good stability over a broad frequency and temperature ranges, are required for some of modern electronic applications
The dielectric constant (ε′) increases with the weight fraction of CCTO, for each of the analyzed frequencies, and a similar behavior is observed for ε. e real part of the complex permittivity for the pure polyvinyl alcohol (PVA) samples was 5.5 at 2.7 GHz and 5.3 at 5.0 GHz
Two resonant cavities with 2.7 GHz and 5.0 GHz resonant frequencies were used to measure the complex permittivity of polymer matrix composites, prepared by the dispersion of CCTO (CaCu3Ti4O12) powders, prepared by the solid-state method, in a polyvinyl alcohol (PVA) matrix

Summary

Introduction

Materials with excellent dielectric properties, such as a highdielectric constant, low dissipation factor, and good stability over a broad frequency and temperature ranges, are required for some of modern electronic applications. In the last few years, it has emerged an increasing interest in size reduction and performance enhancement of embedded passive components, especially for embedded capacitors [1,2,3]. Materials for such kind of applications must present (beyond the already mentioned properties) good dielectric and thermal stability over a broad frequency and temperature ranges. The final piece should be manufactured in a simple way, with low production costs To achieve this goal, many trials were performed with ceramic-polymer composites with high-dielectric constant [4,5,6,7]. It is well known that, for some applications, they are too brittle which becomes a critical factor

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Conclusion