Phase formation and texture development in mullite/zirconia composites fabricated by templated grain growth

Mullite is a promising candidate for advanced ceramic applications but its low fracture toughness and difficulties in sintering are the main limitations for more widespread industrial applications. Therefore, mullite/zirconia composites were prepared from a reactive mixture of alumina and zircon powders. Additives, TiO2 and MgO, were used to modify aluminosilicate glass to increase densification and <001> aluminum borate templates were incorporated to texture mullite in [001] by templated grain growth. Mullite/zirconia phase formation was complete at 1450◦C in the presence of both templates and additives, as compared to 1500◦C for the samples with only additives and to 1600◦C for the samples with only templates. Dense mullite/zirconia composites with highly <001>-textured mullite grains (Lotgering factor ∼1) and a retention of ∼13% tetragonal ZrO2 were fabricated after sintering at 1450◦C for 2 h. A high quality of mullite texture with a degree of orientation parameter of 0.22 and a narrow distribution of elongated mullite grains within 8.8◦ around [001] were successfully obtained in the composites. C 2006 Springer Science + Business Media, Inc.