Sintering of mixtures of seeded boehmite and ultrafine α-alumina

alpha-Alumina was fabricated by dry pressing mixtures of seeded boehmite and fine alpha-alumina (i.e., 0.2 and 0.3 mu m diameter) to reduce the large shrinkage of boehmite-derived alpha-alumina. The maximum green density was obtained with mixtures containing similar to 70% alpha-alumina for both alumina powders. The similar to 15% linear shrinkage and microstructures of these samples were comparable to 100% alumina powder samples. Samples with 0.2 mu m alumina sintered to densities >95% at 1300 degrees C whereas 1400 degrees C was needed for samples with 0.3 mu m alumina. These results indicate that boehmite can be used as a substitute for relatively expensive ultrafine alpha-alumina powders.