Microwave absorption studies of BaCoTi ferrite composites (original) (raw)
A ferrit e series of the compos iti on BaFeI2_2,CoxTixOI9. wherein x varies from 0.0 to 0.9 in steps of 0.2. has been prcpared by the standard ceramic technique. The microwave absorption studies of ferrite-polymer composites with different till-factors have been made in the freq uency range from 8.6-12.4 GHz. A maximum return loss of 14.7 dB has been obtained for compos ites with x equ al 0.3 and absorber thickness of 4.0 mm at 9.2 GH z. The dependence of matching frequency on composition is appa rent for this thickness. The maximum values of dc resistivity and th e Curie tem perature have been found to be 234.8 kQ and 469°C respectively. These values correspond to the same composition for which the return loss is the maximum. A dependence of return loss on complex dielectric constant and permeability has been investigated in the X-band. The magnetic dielectrics, such as M-type hexaferrites, are known to be effective microwave absorbers due to their lossy interaction with the electric and magnetic fields of microwaves, which transforms the microwave energy to thermal energyl.5. The complex permeability and permittivity affect the reflection and atten uation characteristics of these materials. The composites of such ferrites with suitable polymers are quite useful as they can be easily shaped and converted into a paste or a paint that can be applied on the objects of interest. The absorption characteristics of ferrite-po lymer composites depend on the composition of ferrite, nature of polymer, fill factor and thickness of composite layer and can be tailor-made by altering these parameters. Barium hexaferrite has been extensively used for producing permanent magnets and microwave devices 6. The substitution of C0 2 +Ti 4 + ions for Fe 3 + ions in Ba-ferrite is expected to change the anisotropy constant and modify the properties so as to make them effective microwave absorbers. In the present work, we report the microwave absorpt ion characteristics of substituted BaCoTi hexaferrites obtained fro m the observed variations of permeability and permittivity as a function of C0 2 +Ti 4 +-content at different frequencies. It helps to determine the optimum amount of C0 2 +Ti 4 + ions in Ba-ferrite, which yields a minimum reflection loss over a wide freq uency range.
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