Effects of Zn2+-Zr4+ ions on the structural, mechanical, electrical, and optical properties of cobalt ferrites synthesized via the sol-gel route

In the present study, we examined the effects of doping with Zn-Zr on the structural, optical, electrical, and mechanical properties of cobalt ferrite. Nanocrystalline cobalt ferrites comprising CoZnxZrxFe2-2xO4 (x = 0.0 to 0.4, Delta x = 0.1) were prepared via the sol-gel route. X-ray diffraction analysis indicated the formation of a spinel phase in the ferrites. An additional ZrO2 phase was observed for x = 0.3. Characteristic absorption bands at frequencies of 580-610 cm(-1) and 375-400 cm(-1) related to spinel structures were observed in the Fourier transform infrared FTIR spectra obtained for the ferrites. The elastic constants decreased as the Zn-Zr contents increased. The longitudinal and shear velocities of ultrasound through the ferrite materials were measured using the ultrasonic pulse transmission method. The variations in the ultrasound velocities could be attributed to the changes in density. The dielectric parameters epsilon' (dielectric constant) and tan delta (dielectric loss tangent) were analyzed as functions of the frequency and Zn-Zr composition. Both epsilon' and tan delta decreased as the frequency and Zn-Zr contents increase. The variations in the values of parameters epsilon' and tan delta were explained using Maxwell-Wagner interfacial polarization according to Koops phenomenological theory. The values of the activation energy and Curie temperature were calculated based on plots of the thermal variation in the direct current resistivity. The activation energy values indicated that electron hopping was the mechanism responsible for conduction in the ferrites.