مكانيزم تشكيل بلورهاي در حد نانومتر هگزافريت باريم در روش سل - ژل احتراقي

Mechanism of the Formation of Nano -crystalline Barium Hexaferrite in the Sol-Gel Combustion Method

Nano crystalline particles of baruim hexaferrite (BaFe12O19) have been prepared at a relatively low temperature of 700°C by a sol-gel combustion technique using a gel including citric acid as a fuel/reluctant and nitrates as oxidants. The results revealed that the nitrate citrate gels exhibit a self-propagating behavior after ignition. The thermal decomposition process of the nitrate citrate gels and as-burnt powders was investigated by XRD and DTAITG techniques to study phase evolution. Unlike other ferrites, Ba-hexaferrite was not synthesized directly by sol-gel combustion method, but was formed gradually from some intermediate phases due to its complicated crystalline structure. The SEM investigation revealed that the mean particle size of barium hexaferrite increases with increasing calcination temperature. The magnetic properties measured using a VSM showed relatively high values of coercivity (5.lkOe) and saturation magnetization (61.2emu/g), at 14kOe, for well crystallized BaFe12O19 sample calcined at 1000°C.