A citrate process to synthesize nanocrystalline zinc ferrite from 7 to 23 nm crystallite size

Nanosized zinc ferrite of controlled crystallite size has been prepared by calcining an amorphous zinc-iron-citrate precursor at different temperatures up to 650 degreesC. The variation of crystallite size with calcination temperature has been investigated using X-ray diffraction (XRD), thermogravimetry-differential thermal analysis (TG-DTA), and transmission electron microscopy (TEM), and a recipe for the preparation of nano zinc ferrite of desired size has been developed. Zinc ferrite has been found to crystallize at temperatures as low as 200 degreesC and calcination time as little as 1 h. The crystallite size varied from 7 to 23 nm as the calcination temperature was increased from 200 to 600 degreesC. It has been observed that the crystallization of zinc ferrite from the amorphous powder is complete at 350 degreesC, forming 7-nm crystallites. Calcination at higher temperatures leads to a linear growth of the crystallites from 7 nm at 350 degreesC to 23 nm at 600 degreesC. (C) 2003 Elsevier Science B.V. All rights reserved.