Studies on characterization, microstructures and magnetic properties of nano-size barium hexa-ferrite prepared through a hydrothermal precipitation-calcination route

An attempt was made to prepare nano-size barium hexa-ferrite particles following a hydrothermal precipitation-calcination route using barium and iron nitrate solutions. During hydrothermal treatment at 180 degreesC (2 h precipitation time) barium carbonate and hematite phases were formed. This precursor was calcined at 800, 1000 and 1200 degreesC to determine the conditions for obtaining barium hexa-ferrite. The characterization studies on calcined products revealed that up to 800 degreesC, the major crystalline phases (barium carbonate and hematite) of the precursor were retained. At 1000 degreesC, formation of barium hexa-ferrite started and at 1200 degreesC, though most of the major peaks of X-ray diffractogram corresponded to barium hexa-ferrite, a number of peaks corresponding to hematite were also present. Some low intensity peaks for barium carbonate were observed. The average particle size was 40 nm. Saturation magnetization, remanence magnetization and coercivity were found to be 40.0, 21.6 emu g(-1) and 2.87 kOe, respectively. The values obtained both for coercivity and magnetization for the present sample were lower than the reported bulk values which could be due to the fact that the sample prepared through the present technique was not mono-phasic. (C) 2004 Elsevier B.V. All rights reserved.