Soaking time effect on the structural and dielectric properties of microwave sintered cobalt ferrite nanomaterials

Abstract Auto-combustion method was employed to synthesize cobalt ferrite nanopowders having structural formula CoFe2O4. Then the as-prepared sample was calcined at 600°C in a microwave furnace for 30 minutes at 5°C/min heating rate. The calcined sample was given microwave sintering at 700°C at the same heating rate for three different soaking time viz. 2 hours, 4 hours and 6 hours. Phase confirmation of the sintered samples was done using XRD data. The presence of metal oxide bonds in the samples was confirmed by FTIR spectra. From the XRD spectra, crystallite sizes, lattice constants, theoretical densities and porosities of the samples were found out. Dielectric properties such as dielectric constant, dielectric loss, impedance and ac conductivity of all the samples were studied using Agilent LCR meter in the frequency ranging from 20 Hz to 2 MHz. Variation of dielectric constant and dielectric loss with frequency showed normal dispersive behaviour of ferrites which can be explained using the Maxwell-Wagner model. With increasing soaking time, the dielectric loss increased but the opposite trend was observed for the dielectric constant at the higher frequency region. As the frequency increased, the ac conductivity of the samples increased owing to enhanced hopping of electrons between cations. Impedance values of the samples were found to decrease slightly in the low-frequency region and swift decrease in the high-frequency region. Soaking time effects on the ac conductivity were also reported.