Influence of the type of fuel used for the solution combustion synthesis on the structure, morphology and magnetic properties of nanosized NiFe2O4

Single phase nanosized NiFe2O4 powders were prepared by a solution combustion method with the use of four different types of fuel (two of them containing nitrogen and the other two - pure hydrocarbons). The resulting materials were characterized with respect to structural and morphological features by using appropriate methods. Magnetization curves were measured at room temperature (RT) using vibrating sample magnetometer (VSM) in fields up to 6 kOe. The study revealed that under identical external conditions such as, oxidizer to fuel ratio, temperature and time of thermal treatment, the type of the fuel used during the synthesis strongly influences the structure and morphology of the spinel oxide products and thus it determines their magnetic properties. The use of nitrogen-containing fuels leads to the preparation of materials with greater particle size (about 60 nm for samples treated at 700 °C), stronger aggregation ability and higher degree of cation ordering than materials prepared with pure hydrocarbons fuels (size 35-40 nm for samples treated at 700 °C). The magnetization for the NiFe2O4 materials with larger particle size, prepared from a nitrogen-containing fuel is 33-36 emu/g, which is higher that of the NiFe2O4 materials, prepared from pure carbohydrates at the same annealing temperatures (23-26 emu/g). The results obtained in the present study give an opportunity to alter the properties of NiFe2O4 powder materials by an appropriate choice of the fuel used in the synthesis.