The nanosized particle materials of doped-TiO2 with Y2O3 were prepared by means of sol-gel technique for use in electrorheological(ER)fluids,and their crystal structures were measured by X-ray diffraction(XRD)analysis.To compare with the pure TiO2,a distinct enhancement in the shear stress under dc electric field was found by using such materials.This can be explained by the increase of the dielectric loss and dielectric constant at low frequency.The effects of the crystal structure of the particles on the dielectric property and ER performance of materials were investigated.