Preparation of lithium ferrites by coprecipitation

A new process for preparing coprecipitated lithium-containing ferrites is presented. Chemical coprecipitation results in a fine particle powder which, if properly sintered, yields fast switching memory cores. Ferrites containing Fe, Mn, Ni, Zn, etc., are readily coprecipitated because of the insolubility of their hydroxides and oxalates. Lithium, because of its solubility, cannot be precipitated as a hydroxide or oxalate in an aqueous solution, but it was found that it can be coprecipitated in the form of a stearate from an ammonium or tetramethylammonium hydroxide-stearic acid solution. The other elements are coprecipitated from the solution as hydroxides. The stearate is burned from the dried precipitate powder, leaving a ferrite with a specific surface area of 40 m²/g. The switching speed of cores fabricated from coprecipitated lithium manganese ferrite is improved compared to cores prepared by the mixed oxide process but only at the expense of a higher drive.