Preparation and magnetic properties of barium ferrite fine particles by the coprecipitation salt-catalysis method

The authors describe catalytic action by NaCl in the reaction between α-Fe₂O₃ and BaCO₃ and the development of a new process for manufacturing barium ferrite fine particles. Pure α-FeOOH and reagent-grade BaCO₃ are mixed and heated at temperatures from 300 to 800°C with and without NaCl. The BaCO₃ and α-Fe₂O₃ powders which are formed during heating react and change to barium ferrite at temperatures 100°C lower than NaCl than without it. A hematite defect structure is maintained up to a relatively high temperature due to the presence of the salt, which promotes the formation of barium ferrite. The manufacturing process involves mixing an aqueous solution of metallic chlorides with a mixture of NaOH and Na ₂CO₃. This alkaline coprecipitate slurry is then neutralized by HCl solution, filtered, and dried. The dried powder, containing salts produced by the reaction, is heated at 840°C. After the salts are dissolved in water, barium ferrite fine particles are obtained