Strength and fracture mechanisms in beta-alumina

The fracture stress, fracture initiation energy and work of fracture have been measured for a fine grained beta-alumina ceramic. The fracture stress has been shown to be naturally distributed and can be described by the Weibull distribution function. Values of the fracture initiation energy and work of fracture were found to be similar, 25 J m^–2.The microstructure of beta-alumina has been examined using transmission electron microscopy. In thin foils of the fine grained material cleavage cracks were invariably found to occur in the basal layers. The phenomena has been explained empirically in terms of atomic bonding of the mirror plane. Contributing terms to the fracture energy t have been discussed and it is suggested that lamination and deformation at the crack tip by generation and movement of dislocations along basal planes is a significant factor.