Effects of pH and citric acid contents on characteristics of ester-derived BaFe12O19 powder

The single domain size of BaFe12O19 powder with crystallite sizes less than 200 nm was produced using a citric acid precursor method. Fe3+ and Ba2+, in a molar ratio of 12, were chelated by COOH- in an aqueous solution. After ethylene glycol additions, esterification, dehydration, and calcination led to the formation of ester-derived BaFe12O19 powder. High pH and/or high citric acid contents in the starting solution are required to complete chelate metallic ions in the solution and to form pure barium ferrite powder at 1073 K. Pure single magnetic domain BaFe12O19 particles of M(30 kOe) approximate to 54 emu/g, M-r approximate to 28 emu/g, and H-c approximate to 3.7 kOe were produced using [citric acid]/[metallic ions] = 1.5 and pH greater than or equal to 7. (C) 2002 Elsevier Science B.V. All rights reserved.