Nature of abnormal grain growth in (Ba,Nb)-doped TiO2 ceramics and effect of crystal phases in starting powders

[[abstract]]The effect of crystal phase in the starting powder of (Ba,Nb)-doped TiO2 ceramics on abnormal grain growth was investigated. The abnormal grain growth took place mainly during the cooling period after the second phase precipitated. The extent of abnormal grain growth is higher in an anatase powder sample than in a rutile powder sample and is highest at an intermediate rate of cooling for both powders. The nature of abnormal grain growth is suggested to be the Ba flow resulting from the concentration gradient of Ba between neighboring grains as the second phase precipitated. The reason for the greater abnormal grain growth in the anatase powder sample is proposed to be the higher dissolution of Ba in the grain which can be explained by the more open crystal structure of anatase with respect to rutile. The amount of second phase on the surface is greater than that in the interior, especially in the anatase powder sample. Characteristic features of the structure of anatase were calculated[[fileno]]2020301010030[[department]]材料科學工程學