Effect of La-doped on Structure of Nanosized SnO_2 by Chemical Co-precipitation Method

La-doped nanosized SnO_2 powders are prepared by chemical co-precipitation method using SnCl_4 and LaCl_3 as raw materials. The structure and granularity of nanosized SnO_2 are investigated by differential scanning calorimeter and thermo-gravimetric analysis (DSC-TG), X-ray diffraction (XRD) and transmission electron microscope (TEM), the main conclusions can be obtained as follows:(1) the calcination temperature can influence the production. For example, when the La/Sn hydroxide powders are calcinated under 400～650℃, the production is SnO_2, when it is 750℃ upwards, the major composition are La_2Sn_2O_7 and SnO_2.(2)La-doped can efficiently prevent the growing-up of nanosized SnO_2 by hinder the transformation of SnO_2 from non-crystal to crystal. Once the crystal is formed and the size reached a critical value, then La startes to separate from SnO_2 and the reaction production is La_2Sn_2O_7, here the function of preventing the growing-up of nanosized crystal disappeares, and the grain can growing-up quickly.