REACTION SINTERING OF ALUMINUM TITANATE .2. EFFECT OF DIFFERENT ALUMINA POWDERS

Reaction sintering of aluminium titanate was studied starting from different commercial alumina powders and rutile. The formation of titanate, the successive sintering process and the corresponding microstructure evolution have been investigated using differential dilatometry, X-ray powder diffraction and scanning electron microscopy. Reaction sintering of pure Al2TiO5 results in a coarse-grained material with low density; the dependence of the average grain size of the resulting material from the level of impurities of the starting alumina is qualitatively discussed; the purest aluminas result in the largest grains. Addition of 2 wt% of MgO changes the mechanism of titanate formation, resulting in a strong reduction of the average grain size and remarkable influence on densification of the final material. Since final microstructure is mainly determined by the amount of MgO added, the influence of the nature of alumina powder is less pronounced in comparison with pure Al2TiO5.