Effect of microstructure, grain size, and rare earth doping on the electrorheological performance of nanosized particle materials

Nanosized particle materials with different structures and grain sizes were prepared by doping TiO2 or ZrO2 with rare earth (RE) elements, and by changing the method of treatment. Their microstructures were confirmed by X-ray diffraction (XRD) analyses and measurements of the surface areas, pore volumes, and pore sizes of the particles. The electrorheological (ER) performance and dielectric properties of these materials, and the relationship between ER activity, microstructure, and grain size of these particle materials were investigated. The results have shown that RE doping can either increase or decrease the ER activity of a material, which is related to the pore volume in the grain. Body-centered tetragonal TiO2 and tetragonal ZrO2 possess higher ER activity than tetragonal TiO2 and monoclinic ZrO2, respectively. The effect of grain size on ER performance should not be neglected for different materials in a system with identical crystal structure and composition, and the co-action of both larger grain size and larger pore volume can play a very important role in nanosized particle materials. Optimal matching between appropriate RE-doping, microstructure and particle size, which can be achieved by fine-tuning the production process of a material, may provide a basis for producing an ER material with high activity.