Preparation and magnetic properties of La-Mn and La-Co doped barium hexaferrites prepared via an improved co-precipitation/molten salt method

LaMn and LaCo doped barium hexaferrites of formula Ba(1-x)LaxFe(12-x)MxO19 (M=Mn, Co) (x=0.05 to 0.40) were prepared with an improved co-precipitation/molten salt method. For the synthesis, aqueous solutions of the appropriate metal chlorides were prepared in the ratio required except that the initial mole ratio of Fe and dopants to Ba was chosen to be 11:1, and then mixed with excess Na2CO3. The solutions were then cooled, filtered off, dried, then mixed with KCl flux, and heated at 450 degrees C and for 2 h. The temperature was then raised to 950 degrees C and kept for 4 h, then cooled. This new synthesis method, which employs a lower temperature and shorter reaction time, gives products with improved crystallinity and purity while the saturation magnetization and coercivity values are comparable with those synthesized via the high temperature method. (C) 2010 Elsevier B.V. All rights reserved.