Preparation of nano-sized manganese ferrite (MnFe_2O4) via coprecipitation method

摘要

Nano-sized manganese ferrite (MnFe_2O_4) powder has been synthesized via coprecipitation method, using FeSO_4.7H_2O and MnSO_4.H_2O 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_2O_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.