Síntese, caracterização e estudo das propriedades dielétricas de ferritas Ni1-Xznxfe2o4

Abstract

The ferrites are compounds with molecular formule AB2O4 type (where A is a divalent cation in tetrahedrical site and B is a trivalent cation in an octahedrical site) and generally have a spinel structure. They are materials that show ferrimagnetic behavior. The ferrites can be synthesized in some ways, which are: co-precipitation route, solid-state route, sonochemical, sol-gel, hydrothermal, and some others synthetic routes. The coprecipitation method was the synthetic route chosen to synthesize Ni0,5Zn0,5Fe2O4 and ZnFe2O4 ferrites. When the ferrites show nanometrics dimensions (nanoparticles), they show superparamagnetic character if they have dimensions smaller than the critical size Tc. They also can be a ceramic, with its due crystalline structure. This kind of material can have many types of applications due its dielectric and magnetic properties. These properties are directly linked with the crystalline arrangement of material, and for this, x-ray diffraction method was used for structural characterization of material. For determination of dielectric properties (real permissivity, imaginary permissvity and dielectric loss) were made measurements in an impedance spectrometer in radiofrequency and microwaves range. Changing in temperature changes the vibrational state of atoms in material structure, which consequently, changes its properties, for this reason, impedance measurements in radiofrequency range was made with system temperature changing. The ceramics can resound an electromagnetic radiation with some frequencies within it, in this form is possible determine the frequency of TE 011 (transversal electric mode), this frequency was determinated by the Hakki-Coleman method in microwaves range. This frequency was used to measure antenna properties of material.