Processing of (BaSr)Fe12O19 for antenna miniaturization

Hexaferrites of M-type are investigated for high-frequency applications, owing to their higher ferro-magnetic resonances as compared to traditional magnetic materials, thus ensuring a less dispersive behaviour of the material at microwave frequencies. Here we present the experimental work concerning the ceramic process for the production of the barium-strontium hexaferrite (BSFO). The critical issue in the production of this material is to obtain a fully dense and homogeneous microstructure. These aspects have been addressed by introducing powder grinding processes, and by varying the cold consolidation conditions of the powders. A number of samples of the material have been produced, both for morphological and microstructural characterization and a demonstrator antenna, onto which conductive patches were applied, and the radiating properties of which were tested. Barium-strontium hexaferrite as supporting material for antennas - while allowing substantial device miniaturization - displays relatively high dielectric and magnetic losses.