The addition effects of alkaline earth ions in the chemical synthesis of ε-Fe2O3 nanocrystals that exhibit a huge coercive field -: art. no. 10K312

An iron oxide/silica composite material, which was prepared by combining reverse-micelle and sol-gel techniques, exhibited a huge coercive field H-c of 20 kOe (1.6 X 10(5) Am-1) in our previous work. The key of this synthetic procedure was the added Ba2+ ions that created a single phase of epsilon-Fe2O3. In the present work, the addition effect of Ca2+ ions to this procedure was investigated. Consequently, rod-shape epsilon-Fe2O3 nanocrystals (40-120 nm X 15-20 nm) were obtained and a H-c value of 20 kOe was observed. Thermodynamical analysis that considered the surface energy of nanoparticle suggested that a single epsilon-Fe2O3 Phase was generated by retarding the crystal growth of Fe2O3 particles under the presence of alkaline earth ions. (c) 2005 American Institute of Physics.