Observations on the grain-boundary of Al2O3 bicrystals

Abstract

The grain-boundary thickness of alumina bicrystals, fabricated without the aid of sintering additives and pressure, was measured with an optical microscope. The thickness was 500 to 550 Å and independent of the tilt angle. Impurities segregated at the grain-boundary and the surface of the same sample was studied with an ion microanalyser. The segregation of Ca and Si at both interfaces was noticeable but that of Mg was not. The thickness of the segregation region for both interfaces was 600 to 800 Å. The spheroidization of tubular voids into pores at the grain-boundary was controlled by surface diffusion. Discussion of the fabrication process of the bicrystal in terms of initial sintering kinetics concluded that the process was controlled by the surface diffusion.