The influence of composition, cooling rate and atmosphere on the synthesis and thermal stability of aluminum titanate

The formation and stability of tialite (Al2TiO5) have been studied in equimolar of Al2O3-TiO2 (AT) in specimen, mixtures with excess of alumina or rutile and specimen AT with graphite addition. After firing the specimens at 1400 degrees C/3 h in different atmospheres, they were cooled with two routs, slow cooling in the furnace, and special fast cooling. X-ray diffraction of powders showed that in oxidation atmosphere, tialite formed and some of corunclum and/or rutile remained. In reduction conditions at slow cooling rate in equimolar and nonequimolar Al2O3-TiO2 samples tialite was observed along with corundum, rutile and titanium suboxides but in graphite content specimens tialite was not detected. In fast cooling at AT sample tialite was present but in excess alumina or TiO2 contents and graphite addition specimens tialite was not present. The mechanism of instability of tialite in reducing condition without annealing process was investigated and microstructures of samples were observed. Results showed that in this condition due to transformation of rutile to titanium suboxides, tialite formation severely decreased and/or established at firing temperature during cooling at 1280-700 degrees C and intensively decomposed to parent oxides or high alumina and titania phases. (C) 2008 Elsevier B.V. All rights reserved.