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 °C. 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 °C 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 °C. It has been observed that the crystallization of zinc ferrite from the amorphous powder is complete at 350 °C, forming 7-nm crystallites. Calcination at higher temperatures leads to a linear growth of the crystallites from 7 nm at 350 °C to 23 nm at 600 °C.