Synthesis of nanosized MgFe 2 O 4 powders by microwave hydrothermal method Seema Verma, P.A. Joy * , Y.B. Khollam, H.S. Potdar, S.B. Deshpande National Chemical Laboratory, Physical and Materials Chemistry Division, Pune 411008, India Received 16 May 2003; accepted 15 August 2003 Abstract Nanosized magnesium ferrite, MgFe 2 O 4 , is synthesized under mild microwave hydrothermal (MH) conditions. Powder X-ray diffraction and transmission electron microscopic studies showed that the average particle size of the ferrite obtained is f 3 nm, with a narrow size distribution. Vibrating sample magnetometric studies showed the existence of superparamagnetic state of the ferrite particles. D 2003 Elsevier B.V. All rights reserved. Keywords: Microwave hydrothermal method; Nanomaterials; MgFe 2 O 4 ; Superparamagnetism 1. Introduction Synthesis of nanosized spinel ferrite particles has become an important part of modern ceramic research. Study of nanosized spinel ferrite particles has great relevance to modern technologies including contrast en- hancement of magnetic resonance imaging, high density data storage and magnetic carriers for site-specific drugs delivery [1]. Moreover, synthesis and study of nanosized spinel ferrite particles is of great fundamental interest such as in macroscopic quantum tunnelling [2]. There are several methods for synthesizing nanosized spinel ferrite particles, such as, hydrothermal, coprecipitation, combus- tion, sol–gel, precursor, spray drying and freeze drying, microemulsion and reverse micelle method [3–10] . Among these methods, the hydrothermal method is an efficient low-temperature method of synthesis of ceramic oxides, which is also environmental friendly [11]. How- ever, this method requires prolonged reaction time at low temperatures. The introduction of microwave energy into a chemical reaction, which has at least one component capable of coupling strongly with the microwaves, leads to higher heating rates [12]. Microwave hydrothermal (MH) method is a relatively new technique where the advantages of both microwave heating and hydrothermal method are being made use of. The microwave-assisted hydrothermal route of chemical synthesis of ceramic oxides is yet another novel method of synthesis and is a rapidly developing area of research [13,14]. In recent years, there are several reports where conventional hy- drothermal preparative techniques have been substituted by the microwave hydrothermal method because this method offers rapid heating, faster kinetics, homogeneity, higher yield, better reproducibility, and is economical and energy saver [15–17]. Magnesium ferrite, MgFe 2 O 4 , is one of the important magnetic oxide with spinel structure. Apart from its magnetic applications [18], Mg ferrite is used as catalyst [19], humidity sensor [20], etc. Maehara et al. have recently shown that Mg ferrite is more applicable in achieving local hyperthermia, when compared to other ferrites [21]. Synthesis of nanosized MgFe 2 O 4 is important for its novel magnetic properties, particularly superpara- magnetic behavior [22], and such superparamagnetic par- ticles can be used for different biomedical applications. To the best of our knowledge, no one has reported the synthesis of nanosized MgFe 2 O 4 particles using microwave hydrothermal route. Therefore, in the present investigation, an attempt is being made to synthesize single phase, nanosized, MgFe 2 O 4 particles, with narrow size distribu- tion, by microwave hydrothermal (MH) method, under mild conditions. 0167-577X/$ - see front matter D 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2003.08.025 * Corresponding author. Tel.: +91-20-393300x2273; fax: +91-20-589- 3044. E-mail address: joy@dalton.ncl.res.in (P.A. Joy). www.elsevier.com/locate/matlet Materials Letters 58 (2004) 1092 – 1095