Sol–gel auto-combustion synthesis of Ni0.5Zn0.5Fe2O4/(SiO2)x (x = 10, 20, 30 wt.%) nanocomposites and their characterizations

A nitrate–citrate–silica gel was prepared from metallic nitrates, citric acid and tetraethoxysilane (TEOS) by sol–gel process, and it was further used to synthesize Ni0.5Zn0.5Fe2O4/SiO2 nanocomposites by auto-combustion. The obtained Ni0.5Zn0.5Fe2O4/(SiO2)x (x = 10, 20, 30 wt.%) samples were characterized by IR, 29Si CP/MAS NMR, XRD, TEM, EPR and impedance analyzer measurements. Particle size of these composites was calculated from Scherrerʹs formula, and that decreased with increasing SiO2 content. The content of TEOS in the starting solution affects the interaction between NiZn ferrite and silica, and then determines the particle size, dielectric properties and the EPR properties (ΔHPP, g factor, NS and T2) of the as-synthesized powder.