Abstract
In this study, CoFe2O4 nanoparticles were synthesized using simple, economic and environmentally friend auto-combustion methods including citrate sol-gel, urea, sucrose, Egg-white, gelatin and chitosan methods. Differential thermal analysis-thermogravimetry-differential scanning calorimetry (DTA-TG-DSC) techniques were used to characterize auto-combustion reactions and followed ferrites formation. Structural, morphological, magnetic and electrical properties were studied using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Transmission electron microscopy (TEM), vibrating sample magnetometer (VSM) and conductivity as well as dielectric measurements. XRD showed singlephase ferrites with sizes ranging between 30 and 62 nm depending on the utilized method. TEM showed spherical agglomerated particles with some irregularity in shape with sizes agreed well with those estimated through XRD. FT-IR spectra showed the two characteristic ferrite bands attributed to the stretching frequency of the octahedral and tetrahedral sites. The broadening of the tetrahedral band in case of urea and gelatin methods can be attributed to the low crystallinity. VSM exhibited ferromagnetic characteristics with high remanences and coercivities. The highest magnetization was obtained via sucrose method (67.6 emu/g) while the lowest one was obtained for egg-white route (44 emuig). The obvious variation in the saturation magnetization with different methods can was possibly attributed to the change in sizes as well as the entire cation distribution. The high coercivities obtained suggested their using as permanent magnets or as magnetic recording media. ac-conductivity as a function of temperature indicating semi-conducting behavior with conductivity increases with decreasing size. The changes in the real (epsilon') and imaginary (epsilon") parts of dielectric constant as a function of both frequency and temperature indicated, in accordance with the ac-conductivity study, magnetic transition from ferro- to paramagnetic characteristics for all the samples except for those prepared via sucrose and citrate method. This behavior was discussed in view of the obtained magnetization values. (C) 2017 Elsevier Ltd. All rights reserved.