Dielectric permittivity of nickel ferrites at microwave frequencies 1 MHz to 1.8 GHz

Abstract

NiFe 2 O 4 prepared via the sol-gel technique were pre-sintered at 900°C and synthesized at different sintering temperatures from 1,000°C to 1,200°C at 100°C intervals. The samples were characterized for microwave dielectric properties. These samples were measured using Agilent Impedance/Material Analyzer at frequencies 1 MHz to 1.8 GHz. Results showed a decrease in the dielectric constant and loss factor with frequency except at the turning point, around 150 MHz, where the loss factor showed a gradual increase. However, both the dielectric constant and loss factor increase with increasing sintering temperature. The grain size and density also increased with increasing sintering temperature, but the porosity and grain boundary density showed a decrease.

Morphology and dielectric properties of single sample Ni0.5Zn0.5Fe2O4 nanoparticles prepared via mechanical alloying

“…This is because both porosity and density are inversely proportional to each other and are fractions of theoretical density of the material. The sintered density of the sample is between 4.575 g/cm 3 and 5.179 g/cm 3 or about 86%-97% of the theoretical density of 5.3573 g/cm 3 . The sintering of the nanocrystalline material influences the particle size, shape and crystallization.…”

“…The sample shows high values of   for frequencies lower than 10 3 Hz, but at high frequencies (10 3 -10 6 Hz) as the temperature increases   decreases. At low frequencies the charges have time to accumulate at the borders of the conducting regions causing   to increase, while at higher frequencies the charges do not have time to accumulate and polarization does not occur since the charge displacement is small compared to the dimensions of the conducting region [15].…”

“…The theoretical density for Ni 0.5 Zn 0.5 Fe 2 O 4 is 5.3573 g/cm 3 . The activation energy for grain growth can be predicted from the behavior of particle growth by using the Arrhenius equation below [10]:…”

“…The theoretical density of Ni 0. 5 3 . For the dielectric measurements, the Ni-Zn ferrite pellet was sandwiched between two brass electrodes.…”

“…, where   is the dielectric constant which is the ability of a material to polarize and store a charge within it, whereas the imaginary part   is the loss factor which is a measure of the loss of power usually in the form of heat [3]. Nanoparticles can be synthesized by various physical, chemical and mechanical methods.…”