Abstract
Zn doped manganese ferrites (MZF)/SiO2 (Mn1−xZnxFe2O4/SiO2 (x=0.0, 0.2, 0.4, 0.6, 0.8, 1.0)) nanocomposites with different Mn contents were successfully synthesized by a modified sol–gel autocombustion route using citric acid as a chelating agent and tetraethyl orthosilicate (TEOS) as a source of silica matrix. Silica coatings were done via a modified Stöber method. Optical properties of MnZn-ferrites were improved by coating them with silica. The nitrate–citrate–silica gel exhibited self-propagating combustion behavior, and it is directly transformed into nanosized MnZn-ferrite nanoparticles with spinel cubic crystal structure. MZF/SiO2 nanocomposites show superparamagnetic behavior at room temperature (RT). The highest Ms value is about 73Oe for Mn0.6Zn0.4Fe2O4 sample. This value is slightly less than that of the bulk Mn-ferrite, which is about 80emu/g. The higher Ms value was attributed to cation distribution change from normal spinel to mixed structure. The diffuse reflectance (DR) measurements were applied to determine the band gap (Eg) of samples. The estimated Eg value of SiO2 coated ZnFe2O4 samples (1.95eV) is in accordance with the literature values. Silica coating has a positive impact on the optical band gap (Eg) of MZF/SiO2 nanocomposite. In addition, the raising optical Eg values by increasing Mn content were observed for MZF/SiO2 nanocomposites.
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