The WO3 powder was prepared by a hydrothermal method using formaldehyde as an organic inducer, and characterized by XRD, SEM, TEM and BET. Furthermore, its photochromic properties were studied by a color difference meter. The results indicate that the WO3 is hexagonal and has a particular structure. Under the SEM and TEM observations, it was found that these WO3 microspheres induced by HCOH comprised many WO3 cubes. The edge lengths of the WO3 cube range from 20 to 50 nm, and the average diameter of these microspheres is 500～800 nm. Moreover, the special structure of this induced product provides a better proton diffusion path, thus resulting in its high photochromic properties.

Key words: WO3 powder, photochromism, formaldehyde, organic induce