The main goal of the present research is to study the influence of impurities, at concentrations below the solubility limit, on the evolving microstructure of alumina. The microstructure of a sintered body strongly depends on the composition of the powder used for the sintering process, where dopants and impurities are known to affect sintering rates and grain growth. In this study, the impurity content was varied by doping alumina with different amounts of CaO, below the solubility limit. The Ca concentration was determined by conducting fully standardized wavelength dispersive spectroscopy (WDS) and the change in grain boundary mobility as a function of the amount of dopant was characterized by quantitative analysis of grain size as a function of annealing time, using scanning electron microscopy. Unlike segregating dopants which reduce grain boundary mobility by solute-drag, CaO increases the rate of grain growth. Possible mechanisms by which CaO increases grain boundary mobility will be discussed.
