Preparation of nano‐sized manganese ferrite (MnFe₂O₄) via coprecipitation method

Abstract

Abstract Nano‐sized manganese ferrite (MnFe 2 O 4 ) powder has been synthesized via coprecipitation method, using FeSO 4 ·7H 2 O and MnSO 4 ·H 2 O as starting materials. An aqueous solution of the starting materials, containing Fe 2+ and Mn 2+ in the ratio required in the ferrite, was poured into an NaOH alkaline solution. A greenish precipitate was formed, which carefully washed and dried for 6 h at 80 °C. The dried powder was then heated for 2 h at different temperatures in argon atmosphere and then rapidly cooled to room temperature, using water quenching. XRD patterns of the samples show that the sample annealed at 1050 °C is single phase. Also using Scherrer's formula a mean crystallite size of 80 nm was obtained. Magnetic measurements were performed on cold pressed pellets, using a sensitive permeameter with a maximum field of 1.2 T. The results show that a single phase MnFe 2 O 4 nano‐sized powder can be obtained at annealing temperature of 1050 °C, which is lower than 1250 °C related to the annealing temperature of the same ferrite, prepared by the conventional ceramic technique. Saturation magnetization of the single‐phase sample was 1330 G, which is lower than 5000 G related to a bulk sample. The difference between the values is reasonable, because the magnetic measurements were performed on cold‐pressed unsintered nano sized powders. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)