Abstract: The particles of zinc magnesium aluminum hydrotalcite like compound(Zn-Mg-Al-HTlc) were synthesized by nonsteady coprecipitation method. Their chemical composition, crystal structure, particle morphology and the influence of material ratio were studied. The results show that the molar ratio of (Zn+Mg) to (Zn+Mg+Al) in preparing Zn Mg Al HTlc samples is lower than that of the material, and so is the molar ratio of Zn to (Zn+Mg+Al). However, the molar ratio of Mg to (Zn+Mg+Al) has no changes basically. Pure HTlc phase forms when molar ratio of Al to (Zn+Mg+Al)(x) is between 0.22 and 0.40, and different phases will form beyond this range. When x is lower than 0.22 or higer than 0.40, ZnOor Al(OH)₃ will emerge respectively. The lattice parameters of Zn-Mg-Al-HTlc particles, a = 0.27 -0.32 nm; c =2.27-2.42 nm; basal spacing is in the range of 0.75-0.81 nm. The height of gallery is about 0.30 nm. It was found that the particles of prepared samples are comparatively complete hexagonal plate particles. The particle size is determined respectively by TEM, particle size instrument and XRD-Scherrer formula. It is proved by XRD-scherrer formula that the particle′s mean crystal grain is between 30- 45 nm . The TEM results show that the mean particle size decreases with the decreasing of x . That is, when the content of divalent metal cations increases, the mean particle size decreases. When x is lower than 0.33, the mean particle size is basically lower than 100 nm. Remaining constant x, the mean particle size has an increasing tendency with the increasing of Zn content; with the increasing of Mg content, the mean particle size has a decreasing tendency.

Key words: Hydrotalcite-like compound, Mixed metal hydroxide, Coprecipitation, Ultrafine particle, Sol