Preparation of Co₂Z-Ferrite Fine Powder by Gel-Combustion

抄録

Gel-combustion synthesis was used to synthesize a fine powder of Co₂Z-ferrite (Ba₃Co₂Fe₂₄O₄₁). Either citric acid or glycine was added, as a peptizer, to the mixed aqueous solution of Ba(NO₃)₂, Co(NO₃)₂•6H₂O and Fe(acac)₃. The product gel was ignited at 150°C and then fired again in a temperature range of between 500°C and 1200°C. The ignited product was a mixture of CoFe₂O₄ and Ba(NO₃)₂ when citric acid was used as a gelling agent. Its fired product was a mixture of Co₂Z-, CoY-, BaM-ferrites and BaFe₂O₄. A higher temperature was attained during the ignition of the glycine gel rather than the citric acid gel. The ignited product of the glycine gel was a mixture of CoFe₂O₄ and BaFe₂O₄. Pure Co₂Z-ferrite fine powder was subsequently obtained by firing this ignited product at 1000°C. This temperature is much lower than the firing temperature of 1300°C required by the solid state reaction. Its crystallite and average particle sizes were 42∼48 nm and 180∼200 nm, respectively. Saturation magnetization was 45∼47 emu/g and coercivity was 0.59∼0.90 kOe.