Physical and Dielectric Properties of MnFe2O4 Doped by Mo

Abstract

Background: The properties of spinel ferrites are known to be dependent on many various factors and mainly on the cations distribution among the tetrahedral and octahedral sites. Therefore, they are sensitive to the presence of doping cations, the type and the amount of these cations. Many researchers have focused on investigating the effect of doping on spinel ferrites nanoparticles with various types of dopants. Among the dopants, transition metal (TM) ions have shown significant effects and changes on the structural, optical, electric and magnetic properties of spinel ferrites nanoparticles. Objective: The goal of this work is to investigate the effect of the TM ions Mo5+ on the several properties of manganese ferrites nanoparticles. Methods: Mo-doped manganese ferrites nanoparticles with the general formula MnFe2-xMoxO4 (0≤x≤ 0.1) were prepared by co-precipitation technique using two different methods, depending on the molarity of NaOH and the annealing temperatures. The characterization of the prepared samples was conducted by X-ray powder diffraction (XRD), Energy-Dispersive X-ray (EDX), Transmission Electron Microscopy (TEM), ultraviolet-visible (UV-Vis) absorption spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy in order to investigate the effect of Mo-doping on the structure, crystallite size, morphology, energy gap and functional groups of MnFe2O4 nanoparticles. Vibrating sample magnetometer (VSM) was used to study the magnetic hysteresis of the samples. Results: The XRD patterns show the segregation of MnFe2O4 phase into α-Fe2O3 and Mn2O3 for samples prepared at 4 M NaOH and annealing temperature of 873 K. Whereas, samples prepared at 2 M NaOH without annealing process, obtained a single phase of MnFe2O4. The Eg of both samples decreases with the increase in Mo-doping. FTIR confirms the presence of Fe-O bands corresponding to α-Fe2O3 for annealed samples, and the metal-O bands corresponding to octahedral and tetrahedral sites in non-annealed samples. Magnetic measurements show that annealed samples are antiferromagnetic whereas ferromagnetic behavior is observed in non-annealed samples. Dielectric measurements, for both samples, indicate that the dielectric parameters are strongly dependent on both Mo-concentrations and temperatures. Conclusion: In order to get a single phase of MnFe2O4 nanoparticles, thermal treatment at high temperature and high molarity of NaOH are not recommended. Mo-doping has significant influences on the optical, magnetic and dielectric properties and therefore future studies on the Mo-doping with different and new doping percentages are recommended.