Effect of powder characteristics on microstructures and dielectric properties of (Ba,Nb)-doped titania ceramics

The effect of powder characteristics on the microstructures and dielectric properties of (Ba,Nb)-doped TiO2 ceramics was investigated. Two powders were prepared: one by coprecipitation and the other from mixing of reagent oxides. The powder characteristics were determined by TEM, x-ray powder diffraction, SEM, and centrifugal particle analysis. Extensive abnormal grain growth is observed in samples sintered from coprecipitated powder, while it is not found in samples sintered from reagent oxide powder. The effects of crystallite size, agglomerate distribution, and chemical homogeneity on abnormal grain growth are discussed. A mechanism of abnormal grain growth is given, and chemical homogeneity is determined to be the main factor which caused abnormal grain growth. The effect of powder characteristics on dielectric properties is also described