An additive-free hydrothermal approach has been developed for the large-scale synthesis of lamellar morphology boehmite powders by merely using Al(NO3)(3) and urea as raw materials conducted in an autoclave of 10 L capacity. The hydrothermal synthetic and calcined products were characterized by techniques of X-ray diffraction(XRD), transmission electronic microscopy(TEM), scanning electron microscope(SEM), Fourier transform infrared spectrometry (FOR) and thermogravimetric analysis (TGA/DTA). The microscope analysis manifested that the lamellar boehmite was around 100-200 nm in width and 500-1000 nm in length. The opportune influence factors on boehmite morphology, such as dosage of urea and reaction temperature were determined by single-factor experiment method. To investigate its crystal form and lamellar morphology evolution process, samples subjected to different reaction durations from 2 h to 12 h were prepared and characterized by techniques of TEM, SEM and XRD. A spontaneous morphology evolution mechanism driven by Ostwald ripening was proposed based on the experimental facts. (C) 2013 Elsevier B.V. All rights reserved.