STRUCTURE AND GRAIN COARSENING DURING THE SINTERING OF ALUMINA

The pore surface area and grain-boundary area (S**g**b) were measured during the sintering of undoped and doped (100 ppm MgO) alumina compacts. Since the presence of the additive affects only S**g**b (raising it at a given value of the density), pinning of the boundaries by solid-solution drag is the only additive function evidenced by the results. The importance of such pinning even at densities as low as 75% of theoretical is linked to the existence of microstructural inhomogeneities.