Barium ferrite nanoparticles prepared directly by aerosol pyrolysis

BaFe12O19 nanoparticles. 10 nm in diameter, have been obtained by combination of two methods, the citrate precursor and the aerosol pyrolysis technique. For the first time, well-crystallised barium ferrite particles were obtained by pyrolysis of an aerosol, produced by ultrasonic frequency spraying of a barium iron citrate aqueous solution, in a tubular furnace at 1000 degrees C, without further heat treatment. The reason why the hexaferrite phase forms at lower temperatures than by other methods is the nature of the precursor aerosol solution. The particle size was increased up to 100 nm in diameter by heat treatment at 1000 degrees C in an oven. The obtained particles are spherical aggregates of 400 nm, which can be easily disaggregated by grinding in a mortar. Changes in par-tide size and aggregation state are reflected as changes in the magnetic properties. Saturation magnetisation and coercivity values obtained for the largest particles were similar to those found for commercial Figments, 50 emu/g and 5600 Oe, respectively. (C) 2000 Elsevier Science B.V. All rights reserved.