The effect of post annealing treatment on the citrate sol-gel derived nanocrystalline BaFe12O19 powder: structural, morphological, optical and magnetic properties

The nanocrystalline BaFe12O19 powders were obtained from citrate sol-gel combustion-derived powder upon annealing at 800-1100 degrees C, and explored their structural, micro-structural, optical and magnetic properties. The thermal decomposition of citrate sol-gel combustion product was verified by means of thermogravimetric and differential thermal analysis. Structural identification of the citrate sol-gel combustion powder and annealed samples were investigated by powder X-ray diffraction. Though the combustion product exhibits cubic spinel phase material, the annealed powder yields good quality nanocrystalline hexagonal BaFe12O19 phase materials. The thin plate-like flakes morphology with random particle sizes of similar to 100-200 nm with slightly agglomerated particles of BaFe12O19 phase is analyzed by high resolution scanning electron microscopy for the good quality annealed sample. Photoluminescence emission spectrum of BaFe12O19 material reveals broad emission peak at similar to 360 nm under the excitation wavelength of 270 nm. Interestingly, the near infrared relative reflectivity of the nanocrystalline BaFe12O19 materials obtained by citrate sol-gel synthesis method is higher than the nanocrystalline BaFe12O19 materials obtained by mechano-thermal and co-precipitation method. The present dark brown colored BaFe12O19 materials can be applied as a ceramic color pigment which includes several applications. The room temperature magnetic hysteresis loop of the annealed BaFe12O19 sample exhibits a ferromagnetic saturation magnetization, M-s of 55.774 emu/g at 15 kOe.