Preparation method of nanocrystalline ferrite powders using mechanical alloying process

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PURPOSE : Provided is a method for preparing nanosized Sr-ferrite powder having high coercivity at a lower temperature than a conventional temperature without the use of additives by mechanical alloying process. CONSTITUTION : The nanosized Sr-ferrite, expressed by the formula SrO·n(Fe2O3), 5<=n<=7, is prepared by the following steps of : (i) mixing raw materials and milling mixed powder to nanosized particles by shaker mill, wherein Sr is partially substituted by at least one element selected from Y-contained rare earth elements or Bi, and Fe is partially substituted by at least one element selected from Al, Si, Ti, V, Cr, Mn, Co, Ni, Cu, Zn, etc.; (ii) thermal-treating nanosized mixed powder at 600-1100deg.C; (iii) milling thermal treated powder by roller mill; (iv) annealing milled ferrite powder. The ferrite magnetics are produced by adding SiO2, SrCO3, CaCO3, Al2O3 or Cr2O3 to the step (i), following the step (ii), (iii) and (iv), forming ferrite powder from the step (iv), and sintering. © KIPO 2005