Fracture Properties of Polycrystalline Lithia-Stabilized β“- Alumina

The critical stress-intensity factor, K1C, and the fracture strength, σf, have been investigated on both hot-pressed and sintered lithia-stabilized β”-alumina. The hot-pressed material possessed a strong preferred orientation with many of the basal planes aligned perpendicular to the direction of hot-pressing. Both K1C and σf were found to be orientation-dependent. Two regimes of fracture were identified. In fine-grained material (<120 μm), the strength was slightly dependent on grain size. For larger grain sizes, the strength decreased rapidly with increasing grain size and the fracture mode was almost entirely transgranular. The K1C values for sintered β”-alumina were in the same range as those obtained on the hot-pressed material.