Some main group oxides on mullite phase formation and microstructure evolution

Abstract

Effects of some main group oxides, including SnO2, Sb 2O3 and Bi2O3, on phase formation and microstructural evolution of mullite ceramics in oxide mixtures, have been investigated. The presence of SnO2 has negligible effect on mullite phase formation, while that of Sb2O3 and Bi 2O3 accelerated mullitization, with Bi2O 3 more effective than Sb2O3. No reaction was found between SnO2 and Al2O3 or SiO 2. Sb2O3 reacted with Al2O 3 to form a new compound AlSbO4 at 1100°C, which decomposed at 1200°C. Bi2O3 was not detected by the X-ray diffraction (XRD) measurement even for samples with 20 mol% Bi 2O3. Bi2O3 doping showed a much better effect on densification behavior than SnO2 and Sb 2O3. The effects of the dopants on mullite phase formation and densification behavior could be attributed to their influence on the formation of the low-viscosity liquid phase in the systems. © 2003 Elsevier B.V. All rights reserved.