Publication

Abstract : Phase pure U type hexaferrites having molecular formula Ba4Co2Fe36O60 is synthesized through solid state route as filler for the fabrication of magneto-dielectric (MD) composite. Being a MD material the U type hexaferrite has a promising future in information and communication sector as a base substrate for electronic circuits. Since they exhibit both electric and magnetic properties, they can contribute effectively to circuit miniaturization and bandwidth enhancement compared to an antenna printed on a dielectric substrate. The filler material is then blended with PP (Poly Propylene) matrix and Magneto dielectric substrates are produced via hot pressing technique. Filler concentration has been varied from 70 to 90 wt. % in PP matrix and ascertained amount of optimum filler fraction for dimensionally stable substrate having acceptable properties. Dielectric and magnetic characterizations have been done using Impedance analyzer. It is found that the density of the composite and the dielectric constant is increasing with the increase in filler loading up to an optimum level and further filler loading reduces the density as well as the dielectric constant due to increased porosity. For optimum filler loading a maximum density of 2.96 g/cm3 is achieved. Relative permeability values are found increasing with filler loading even beyond the optimum filler loading. The optimum loaded poly Propylene/Ba4Co2Fe36O60 composite has an effective dielectric constant of 9.21, loss tangent of 0.083, relative permeability of 3.6 and a magnetic loss of 0.060 at 1MHz. Coefficient of thermal expansion (CTE) of the composite has been investigated using thermo mechanical analyzer. Moisture absorption rate of the optimum filler loaded composite is studied and found to be less than 0.1%. Relatively good dielectric constant, low loss tangent together with better relative permeability make the Ba4Co2Fe36O60 filled PP composites an excellent choice as Microwave substrate.