The influence of electric fields on grain boundary mobility in alumina

The influence of an electric field on grain growth of polycrystalline alumina was evaluated. Systematic annealing experiments on fully dense undoped alumina samples were performed in a spark plasma sintering (SPS) furnace at 1600 °C, where heating was either by a current through the graphite die (conventional SPS), or via external heating elements. The grain sizes after annealing in different atmospheres and for different times were measured from polished and thermally etched cross-sections of the samples. A significant increase in the average grain size as a function of time was observed for the samples annealed in SPS with an electric field. SPS with an applied electric field seems to promote grain growth in alumina, although alumina is a non-conductive ceramic (electronic or ionic).