An investigation was carried out concerning the effect of mullite seed particles on phase development, densification behavior, and microstructure evolution in powder compacts prepared with silica/alumina microcomposite particles. The incorporation of ∼2 wt% seed particles in the microcomposite powder compacts had relatively little effect on densification, but resulted in significant decreases in the temperature for mullite formation and the grain sizes in mullitized samples. Samples could be sintered to almost full density and subsequently converted to mullite with average grain sizes ≤0.4 μm at temperatures in the range of 1300°‐1400°C. The available evidence indicated that mullite formation occurred primarily by nucleaton and growth in the siliceous matrix phase.

The microstructure and chemistry of grain-boundary phases in silicate-doped YZO3-ZrO2 ceramics were evaluated by analytical electron microscopy. Two different silicate compositions were used: one an aluminosilicate and the other a horosilicate glass. These grain-boundary phases had a significant impact on the grain morphology, the chemical composition of the grains, and the crystallization of second phases. These results indicate that controlled additions of specific glass phases may provide a means for tailoring the microstructure and physical properties of zirconia ceramics. [