NANO-MAGNETODIELECTRIC COMPOSITE BASED SUBSTRATE FOR USE IN MICROWAVE PLANAR DEVICES IN X-BAND

Arunav Phukan, Nidhi S Bhattacharyya

Abstract: Magnetodielectric materials provide a new dimension for developing miniaturized substrates for microwave applications. Miniaturization in microwave planar devices depends on both the real part of complex permittivity (er) and complex permeability (µr) of the substrate. Major shortfalls of using high er substrates are lowering of radiation efficiency, pattern degradation (due to excitation of surface waves) and lowering of impedance bandwidth. Miniaturization can also be achieved by modifying the other parameter µr . Bulk ferrites, generally, have high saturation magnetization and dispersive magnetic losses and needs strong external dc-bias fields to alter its permeability property, making it unsuitable for compact applications. Nano sized ferrites are reported to have low saturation magnetizations and low eddy current losses. Composites made using nano ferrite inclusions in polymers can result in natural magnetodielectric materials with low magnetic losses. The current study aims to develop low loss flexible nano-magnetodielectric composite based substrates for use in microwave planar devices in X-band (8.2-12.4 GHz). Co0.65Ni0.35Fe2O4 embedded in SiO2 matrix is synthesized using a modified sol-gel method starting from tetraethylorthosilicate (TEOS) and metal (FeIII , CoII , NiII) nitrates and ethylene glycol. Two synthesis routes are chosen (one with H2O being added externally and one without) and the obtained powders are annealed at different temperatures (500-1000 0C) and characterized using XRD. The powders are mixed in 1:1 ratio with silicone for obtaining a flexible structure. Microwave characterizations of the flexible substrates are then carried out to determine the losses in the X-band regime.

Keywords: COMPOSITE

DOI: https://doi.org/10.15623/ijret.2017.0613009