Modelling effective electromagnetic properties of composites containing barium strontium titanate and/or nickel zinc ferrite inclusions from 1 to 4 GHz

摘要

The importance of nonlinear dielectric and magnetic materials for developing nonlinear transmission lines for high power microwave applications necessitates characterization of the behavior of composites containing these inclusions at microwave frequencies. Here, we apply commercial finite element software and various effective medium theories (EMTs) to predict the effective permittivity and permeability of composites containing inclusions with volume fractions of up to 25 % barium strontium titanate (Ba2/3Sr1/3TiO3, BST) and/or nickel zinc ferrite (Ni1/2Zn1/2 Fe2O4, NZF) in a silicon-based host from 1 to 4 GHz. The modelling results suggest that limited agglomerations of high dielectric contrast BST inclusions may create effective higher aspect ratio inclusions that may enhance the effective dielectric properties of BST composites. For the three-phase composites containing BST and NZF in polydimethylsiloxane (PDMS), we first treated the NZF and PDMS as an intermediate "host," which we subsequently mixed with BST inclusions to construct an effective two-phase EMT. The modelling results agree with the measured permittivity and permeability of the two- and three-phase composites in the linear region and may be used as predictive tools to guide composite design.