YVO4 photocatalysts with different grain sizes were obtained by annealing the YVO4 nanopowders synthesized via microwave irradiation. The products were characterized by X-ray diffractometer (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), surface area and porosity analyzer, and ultraviolet-visible (UV-vis) spectrophotometer. Photocatalytic measurements showed that the YVO4 nanopowders with grain size of about 5 nm possess superior photocatalytic properties in decolorization of methyl orange solution. (c) 2006 Elsevier B.V. All rights reserved.