Effect of ZrSiO2 and MgO additions on reaction sintering and properties of Al2TiO5-based materials

Two sets of Al₂TiO₅-based composites were prepared by reaction sintering of (a) Al₂O₃/TiO₂/ZrSiO₄ and (b)Al₂O₃/TiO₂/ZrSiO₄/MgO powder mixtures. The influence of the variation of ZrSiO₄ content (0 to 10wt%) and the addition of 2 wt% MgO on the reaction-sintering process, microstructure, mechanical and thermal properties, were evaluated. ZrSiO₄ addition shifted the Al₂TiO₅ formation to higher temperatures, whereas MgO accelerated both Al₂TiO₅ formation and ZrSiO₄ decomposition. The presence of ZrSiO₄ and an excess of Al₂O₃ generated a dispersion of ZrO₂ and mullite particles in the grain boundaries and enhanced simultaneously the densification process. After sintering in the temperature range 1350 to 1500 ° C, the obtained composites exhibited significantly higher bending strength than the monophasic aluminium titanate (up to 80 M Pa). Al₂TiO₅ (80wt%)-mullite-ZrO₂ composites which combined good mechanical strength (55MPa), low thermal expansion (_20–1000C < 1 × 10^–6 K^–1) and excellent thermal stability were obtained by reaction and sintering of powder mixtures containing both ZrSiO₄ and MgO.