A simple and novel method was developed to synthesize Mg-Al-CO₃ hydrotalcite. With this method, Mg^2＋/Al^3＋/CO₃^2－ hydrotalcite with molar ratio of 6∶2∶1 was hydrothermally synthesized. The synthesized Mg-Al-CO₃ hydrotalcite samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FE-SEM), transmission electron microscope (TEM), high resolution transmission electron microscopy (HRTEM) and thermal analysis (TG-DSC). The FE-SEM, TEM and HRTEM images show that the hydrotalcite has morphology of a homogeneous and regular hexagonal sheet with thickness of about 20 nm. The XRD results indicated that the synthesized Mg-Al-CO₃ hydrotalcite was well crystallized. Furthermore, the distribution of particle size was analyzed with dynamic light scattering technique. The results are consistent with the SEM images and the measured diameter of each hexagon in hydrotalcite is about 350 nm. The effects of preparation condition on the micro-structure were also investigated. It is found that the diameter of the sheet crystal, rather than the morphology, is influenced by hydrothermal treatment temperature and time, indicating that increasing treatment temperature and time only results in larger hexagonal crystal.

Key words: hydrotalcite, hydrothermal synthesis, crystal morphology, particle size