Faceting behavior of Al2O3 in the presence of glassy phase

Abstract

It is well known that A1203 can reach near-theoretical density by a liquid-phase sintering process in which an amorphous glass phase containing SiO2, CaO and Al2O3 helps density Al2O3. Understanding the faceting behavior of Al2O3 in the presence of such a glass phase is important since the movement of the facets and the type of facets that form during the liquid-phase sintering process determine the final microstructure of the grain boundaries that ultimately control the properties of Al2O3 compacts. As a part of a larger study on the role of impurities in the sintering process of Al2O3 compacts, a new investigation has been carried out to examine the nature and the type (e.g. facet planes) of the crystalline Al2O3, / amorphous glass interface in systematic experiments in which densification aids such as SiO2, CaO and MgO are reacted with single crystal Al2O3. Substantial anisotropy, both from an energy consideration and a kinetics consideration, in the Al2O3/ glass interface is to be expected, and has been observed in this investigation.