Sh. Moradi - Chemistry Department, North Tehran Branch, Islamic Azad University, Tehran, Iran.
S. S. Madani - Chemistry Department, North Tehran Branch, Islamic Azad University, Tehran, Iran.
G. Mahmoudzadeh - Chemistry Department, North Tehran Branch, Islamic Azad University, Tehran, Iran.
M. Zhalechin - Chemistry Department, North Tehran Branch, Islamic Azad University, Tehran, Iran.
S. A. Khorrami - Chemistry Department, North Tehran Branch, Islamic Azad University, Tehran, Iran.

The aim of this study is to evaluate the influence of pH on the synthesis of nanocrystallines cobalt ferrite by combination of sol- gel auto combustion and ultrasonic irradiation methods. Two different fuels, urea and thiourea, along with metal nitrates (oxidant) were used to prepare CoFe۲O۴ powders. The morphology of the resulting powders was investigated. The powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Phase pure spinel cobalt ferrite powder was obtained at pH values ۶ and ۷ after the calcinations at ۷۵۰˚C when urea was used as the fuel; however, the samples obtained using thiourea fuel contained impurities. The average crystalline size was ۲۱ and ۳۷ nm, respectively, for the samples containing urea and thiourea.

Nanocrystalline, CoFe۲O۴, Sol-gel auto-combustion, Fuel, ultrasonic irradiation, XRD, SEM