We reported the preparation of polycrystalline sub-micro ZnO powder using a two-step microwave-assisted synthesis method in which urea and zinc nitrate was used as precipitate to form a uniformity deposition and microwave radiation was employed to form spherical for polycrystalline ZnO particle. The as-prepared ZnO powder was characterized by X-ray diffraction (XRD)

scanning electron microscopy (SEM) and photoluminescence spectra (PL). The results showed that zinc nitrate was in decomposing urea solution at 90℃ accompany by methyl methacrylate for 2 h. After microwave-assisted radiation

the uniform ZnO spheres were obtained and the par-ticle size was about 50~100nm. For comparing

the non-microwave-assisted sample was also characterized which were c-axis oriented and in rod-like shape. The mechanism on preparation of spherical ZnO powder was discussed in this work. By treatment of microwave radiation

the precursor could be heated in uniform so that Zn

2+

and O

2-

on the surface resolved homogeneously and to promoting spherical ZnO particles easily. X-ray powder diffraction patterns of ZnO sub-micro particles are illustrated. All peaks can be well indexed to the zincite phase of ZnO. No peaks from any other phase of ZnO and impurities were observed

it indicated the high purity of the obtained ZnO sub-micro particles. The PL spectrum showed that there were two main emission peaks in near ultraviolet and visible region respectively. The violet emission located at 420nm with a FWHM of 60nm was assigned to a donor-acceptor-type transition or radiative recombination of electrons in conductive band and holes from the valence band. The blue one at 470nm with 30nm FWHM was at-tributed to recombination of trapped electrons and holes from the valence band. ZnO particle morphologies were very complex and diversiform in comparison with that of any other semiconductor. So far

monodispersed ZnO particles with well-defined morphological characteristics

such as

ellip-soidal

needle

prismatic

and rod-like shapes have been obtained

but spherical shape have not been discussed extensively. This paper pointed out a new application of microwave technology in the preparation of spherical ZnO.