Influence of synthesis method on structural and magnetic properties of cobalt ferrite nanoparticles

Abstract

The Co-ferrite nanoparticles having a relatively uniform size distribution around 8 nm were synthesized by three different methods. A simple coprecipitation from aqueous solutions and a coprecipitation in an environment of microemulsions are low temperature methods (50°C), whereas a thermal decomposition of organo-metallic complexes was performed at elevated temperature of 290°C. The X-ray diffractometry (XRD) showed spinel structure, and the high-resolution transmission electron microscopy (HRTEM) a good crystallinity of all the nanoparticles. Energy-dispersive X-ray spectroscopy (EDS) showed the composition close to stoichiometric (*CoFe 2 O 4 ) for both co-precipitated nanoparticles, whereas the nanoparticles prepared by the thermal decomposition were Co-deficient (*Co 0.6 Fe 2.4 O 4 ). The X-ray absorption near-edge structure (XANES) analysis showed Co valence of 2? in all the samples, Fe valence 3? in both coprecipitated samples, but average Fe valence of 2.7? in the sample synthesized by thermal decomposition. The variations in cation distribution within the spinel lattice were observed by structural refinement of Xray absorption fine structure (EXAFS). Like the bulk CoFe 2 O 4 , the nanoparticles synthesized at elevated temperature using thermal decomposition displayed inverse spinel structure with the Co ions occupying predominantly octahedral lattice sites, whereas coprecipitated samples showed considerable proportion of cobalt ions occupying tetrahedral sites (nearly 1/3 for the nanoparticles synthesized by co-precipitation from aqueous solutions and almost 1/4 for the nanoparticles synthesized in microemulsions). Magnetic measurements performed at room temperature and at 10 K were in good agreement with the nanoparticles' composition and the cation distribution in their structure. The presented study clearly shows that the distribution of the cations within the spinel lattice of the ferrite nanoparticles, and consequently their magnetic properties are strongly affected by the synthesis method used.Electronic supplementary material The online version of this article

Effect of zinc concentration on the structural and magnetic properties of mixed Co–Zn ferrites nanoparticles synthesized by sol/gel method

“…Co-precipitation 800 [8] Co-precipitation 850 [30] Co-precipitation in reverse microemulsion 700 [8] Thermal decomposition 1900 [8] Combustion 2002 [30] Sol/Gel (citrate method) 2000 This work Table 3 …”

“…Several preparation techniques have been used for the synthesis of ferrites nano-particles, which exhibit novel properties. Gyergyek et al [8] has reported the synthesis method effect on particles sizes and magnetic properties in Cobalt ferrite using three different techniques: co-precipitation, microemulsion method and thermal decomposition. The results show a significant variation of saturation magnetization and coercitivity.…”

Issues Affecting the Synthetic Scalability of Ternary Metal Ferrite Nanoparticles

“…The syntheses that do exist are often limited to a few selected types of nanoparticles and only use a few different synthetic protocols, despite the fact that the syntheses used may not be the best method to use to make nanoparticles with specific properties [1,2]. It has been shown that different syntheses can lead to vastly different properties, even if the nanoparticles appear the same or very similar in terms of size and shape [1,[3][4][5].…”

Studies on NO2 gas sensing properties of sprayed Co1−xMnxFe2O4 (0≤x≤0.5) spinel ferrite thin films

“…The extensive research on CoFe 2 O 4 thin films has been carried out because of their incredible applications such as gas sensor [5], fabrication of higher frequency device etc., [6][7][8][9]. Recently, cobalt ferrite thin films, substituted cobalt ferrite, and their composites have been used as potential materials for gas sensing applications [10][11][12][13].…”