Ultrafine spherical boehmite (AlOOH) particles were prepared from aluminum sulfate and aluminum chloride solution with urea as precipitant at 90 degrees C. It was observed that mixed surfactants tween80-sodium stearate could improve dispersion of AlOOH particles. While the concentrations of tween80 and sodium stearate were 0.75 wt.% and 0.14 wt.% respectively, particles with spherical degree of 11 and size of 0.36 mu m could be achieved. The thermogravimetric (TG) and Fourier transform infrared spectroscopy (FTIR) showed that sodium stearate molecules were bonded upon the surface of particles forming a coating layer to prevent agglomeration. Addition of NaCl could further improve dispersion of particles, spherical AlOOH particles with average size of 0.38 mu m and nanosized spherical particles could be obtained when the concentration of NaCl was 0.05 M and 0.1 M. At the same time. Al2O3 powders obtained from precursor with NaCl showed much better sintering behavior. (C) 2012 Elsevier B.V. All rights reserved.