TITLE:
Evaluation of Dielectric Mixing Models for the Relative Permittivity of Epoxy/Barium Hexaferrite (BaO·6Fe2O3) Particulate Composites
AUTHORS:
Bekarys Bazarbekuly Tashmukhanbet
KEYWORDS:
Polymer Composite, Barium Hexaferrite, Relative Permittivity, Dielectric Mixing Rules, Effective Medium Theory, Epoxy Resin
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.16 No.7,
July
15,
2026
ABSTRACT: Dispersion-filled polymer composites allow the dielectric response of an insulating matrix to be tailored through the type, size and loading of an embedded second phase. In the present work, the relative permittivity of a two-phase system, consisting of an ED-20 epoxy matrix (ε1 = 3) filled with micron-sized barium hexaferrite (BaO·6Fe2O3, ε2 = 15, effective density 5200 kg·m−3) particles, was studied as a function of filler content and particle size. Composites with spherical filler particles of diameter 2 µm and 20 µm were measured at filler fractions of 0%, 20%, 40% and 60%. Seven classical effective-medium and mixing relations, the Maxwell-Garnett, Lichtenecker, Wagner, Birchak (square-root), Hashin-Shtrikman, Spichnyak-Novikov and Lorentz-Lorenz models—were compiled and evaluated against the data. The effective permittivity increased monotonically with filler content, from 3 for the neat resin up to 9.2 (2 µm) and 5.2 (20 µm) at 60% loading. The fine-particle system is described well by the square-root mixing rule, whereas the coarse-particle system falls below all classical isotropic predictions, indicating a pronounced particle-size (interfacial-area) contribution that the classical size-independent rules do not capture.