Production of mullite-zirconia ceramic composites by reaction sintering

Mullite is gaining an increasing interest among ceramists due to its low thermal expansion coefficient, high melting point and reasonable mechanical strength at room temperature. The fracture toughness and strength of mullite can be improved by the addition of zirconia. Zirconia–mullite ceramic composites can be produced either by the addition of zirconia to mullite or by the reaction sintering of zircon (ZrSi04) and alumina mixtures to obtain zirconia dispersed in mullite matrix. In the present work, the reaction sintering of zircon and alumina has been studied. The bulk density, microstructure and X–ray diffraction studies were carried out on the samples sintered at 1450°C, 1500°C and 1600°C for 1, 2 and 4 hours. The strength of the materials at room temperature was measured by three–point bending and fracture toughness values were obtained by Vickers indentation tests.