Temperature dependence of flexural strength and microstructure of Al2O3/Y3Al5O12/ZrO2 ternary melt growth composites

New Al2O3/Y(3)Al(5)O(1)2(YAG)/ZrO2 ternary Melt Growth Composites (MGCs) with a novel microstructure have been fabricated by unidirectional solidification. These MGCs displayed superior high-temperature strength characteristics. The flexural strength increases progressively in the range 650-800 MPa with a rise in temperature from room temperature up to 1873 K. These excellent high-temperature characteristics are closely linked to such factors as: a microstructure consisting of three-dimensionally continuous and complexly entangled single-crystal Al2O3 with a hexagonal structure, single-crystal YAG with a garnet structure and fine ZrO2 with a cubic structure; characteristic dimensions of the microstructure of Al2O3/YAG/ZrO2 ternary eutectic ceramics of around 2-3 mum for YAG, around 2-3 mum for Al2O3 and around 0.4-0.8 mum for ZrO2; and the fact that no amorphous phase is formed at interfaces between any of the phases. (C) 2002 Kluwer Academic Publishers.