Abstract:
This dissertation discusses the development, characterization and microwave absorption
properties of nanostructured Nickel Ferrite and Nickel-Zinc Ferrite and the influence of
temperature on crystallite size, lattice constant, saturation magnetization and reflection loss.
The effect of loading frequency selective surface (FSS) of double square and triple square
loop on reflection loss was also investigated. Synthesis of the material was carried out by a
sol-gel mediated auto-combustion technique and phase purity was determined by X-ray
diffraction studies and as prepared Nickel Ferrite and Nickel-Zinc Ferrite showed a minimum
reflection loss of-14 dB at 8.3 GHz with a layer thickness of 1.5 mm and -35 dB at 9.7 GHz
with 2.5 mm thickness, respectively. Nickel Ferrite and Nickel-Zinc Ferrite were heat treated
at 500°C and 700°C. The crystallite size of as synthesized samples of nickel ferrite and
nickel-zinc ferrite is 10.8 nm and 16.34 nm, respectively, as calculated by Scherrer's formula.
The complex permittivity, permeability and the reflection loss of the materials were measured
in X-band (8.2 GHz to 12.4 GHz) and the properties were compared for as prepared and heat
treated samples. The parameters such as thickness of layers and material sequences were
optimized using Genetic Algorithm and Artificial Neural Network (ANN). A comparison has
been done on the basis of optimised values for multilaycr absorber provided by two
techniques. The optimized values were then simulated using Ansys l-ligh Frequency
Structure Simulator' for multilayer, double-square and triple-square FSS elements. The
broadening of bandwidth was observed for as prepared Nickel Ferrite and Nickel-Zinc Ferrite
by almost 1 GHz and 1.5 GHz, respectively by the loading of double square FSS. The
fabrication process was proceeded with the as prepared samples and the experimental
verification was done through Attenuation Testing Device (ATD).
