Structure of alumina grain boundaries prepared with and without a thin amorphous intergranular film

The presence of a thin amorphous intergranular film along grain boundaries in alumina is expected to affect the properties of the interface and hence those of the material. In the present study, two types of grain boundaries have been formed in hot-pressed alumina bicrystals. In one case, the surfaces of the sintered crystals were kept as clean as possible, while in the other a thin layer of SiO2 was intentionally deposited onto the surface of one crystal. The distribution of SiO2 was intentionally deposited onto the surface of one crystal. The distribution of SiO2 along the resulting grain boundary was then monitored by transmission electron microscopy and compared with the morphological features of the interface. In the cases chosen, the glass receded into large pores which grew into the alumina itself. However, the presence of the glassy phase during the early stages of sintering clearly did influence the characteristics of the resulting grain boundaries