Dielectric Properties of Composites Based on Ethylene Vinyl Acetate Filled with a Hollandite-Like Ceramic Material K1.5Co0.75Ti7.25O16

Polymer-matrix composites based on ethylene vinyl acetate (EVA) and KxCoyTi8 – yO16 solid solution
with a hollandite-like structure (KCoTO(H)) are obtained and studied as promising materials for components
of electronic devices. The filler is synthesized by modifying X-ray amorphous potassium polytitanate
(PPT) K2O·nTiO2 (n = 4.3) in a CoSO4·7H2O solution under alkaline conditions, followed by thermal treatment
at 900°C. The structure of the synthesized material and the morphology of particles are studied by X-ray
phase analysis (XPA) and scanning electron microscopy (SEM), respectively. KCoTO(H) is introduced in the
EVA polymer matrix by mixing a preliminarily prepared polymer solution and a dispersion of filler powder in
an appropriate solvent in amounts of 10, 20, 30, 40, and 50 vol %. The frequency behavior of the permittivity,
dielectric loss tangent, and conductivity of the obtained composites is studied by impedance spectroscopy. It
is established that an increase in the KCoTO(H) content in the composite contributes to the growth of all the
studied dielectric characteristics of a relatively pure EVA polymer matrix in the entire frequency range of
0.1 kHz–1 MHz (the maximum values are noted at a 50 vol % of the filler and f = 102 Hz: ε = 518, tanδ = 4,
and σ = 1.35 S/cm).