MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF TEXTURED AL2O3

The mechanical properties of a highly textured alumina have been studied and show a significant improvement in bend strength and Weibull modulus when compared to a randomly textured alumina of similar purity. The crystalline texture was due to growth of a small concentration of aligned and uniformly distributed alumina seed platelets into a fine-grained powder matrix during sintering. The (0001) texture of the sintered product gave a non-equiaxed, flattened grain structure, with the c-axis of the hexagonal unit cell approximately normal to the plane of the specimen tiles. This highly textured microstructure drastically reduces the residual stresses which are associated with thermal contraction anisotropy in polycrystalline alumina, and inhibits crack propagation in the through-thickness direction. Two platelet sizes were investigated, the smaller of which gave the smaller final grain size and the better mechanical properties. At 5 wt% of platelet additions the properties were significantly move reproducible than at 10 wt% of the platelets, probably because of significant interference in packing the platelets at the higher loading.