Nanoparticles of Barium Ferrite Synthesised Using a Water-in-Oil Microemulsion

The application of barium f&:e (BaFelZO19; BaF) in the magnetic media industry requires materials with strict control of homogeneity, morphology and magnetic properties resulting from their preparation and pretreatment. Here the use of water-in-oil microemulsions for the synthesis of nanoparticles of BaF is considered. Two microen~ulsions (containmg an aqueous phase, cetyltrimethylammonium bromide surfactant, n-butanol CO-surfactant and octane) were used. The aqueous phase of the first microemulsion contained femc/barium salts and the second cc-precipitant ammonium carbonate. On mixing, the aqueous cores acted as microreactors for cc-precipitation of the BaF precursor which was then separated, dried and annealed (1 198K, 24h) to form BaF. It is shown that microemulsions prepared with different surfactant concentrations lead to part~cles wlth variable but controlled morphology and magnetic properties. In particular, it 1s shown that selecting a microemulsion with a specific concentration can allow coercivity and particle size of product to be nano-engineered.