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

Abstract

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 degrees C in the presence of both templates and additives, as compared to 1500 degrees C for the samples with only additives and to 1600 degrees C for the samples with only templates. Dense mullite/zirconia composites with highly < 001 >-textured mullite grains (Lotgering factor similar to 1) and a retention of similar to 13% tetragonal ZrO2 were fabricated after sintering at 1450 degrees 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 degrees around [001] were successfully obtained in the composites. (c) 2006 Springer Science + Business Media, Inc.