Ultrafine, perfectly spherical Ni–Zn ferrite nanoparticles, with ultranarrow distribution, isolated in a silica matrix, prepared by a novel synthesis method in the liquid phase Original Research Article

Nanocomposites of the type (Ni–Zn)Fe2O4/SiO2 have been synthesized using a novel chemical route involving the liquid phase. Metallic nitrates (MN)–ethylene glycol (EG)–silica gels were prepared as a result of the polycondensation reaction, using as precursors MN of Fe, Ni, Zn and tetraethylorthosilicate, to which EG was added. After gelling and drying, the sols were first subjected to a thermal treatment at a temperature of ∼140 °C, where heteropolynuclear complex combinations with carboxylic ligands are formed as a result of the redox reaction between EG and the nitrate ions. These have been investigated using Fourier transform infrared spectrometry and thermal analysis. The influence of EG on the gels was also studied. While observing the formation of Ni–Zn ferrite using this method, following the thermal treatment of the gels at higher temperatures (500–1000 °C), nanocomposites were obtained made up of ultrafine Ni0.65Zn0.35Fe2O4 nanoparticles (4–6 nm) that are perfectly spherical, with an ultranarrow distribution (∼1 nm) of diameters around the mean value and homogeneously dispersed in a solid SiO2 matrix. The synthesized nanocomposites were characterized by means of X-ray diffraction, high-resolution transmission electron microscopy and magnetic measurements.