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Phase-transformations in amorphous 3Al2O3-2SiO2 system prepared by Sol-Gel method

1988; Elsevier BV; Volume: 14; Issue: 2 Linguagem: Inglês

10.1016/s0272-8842(88)80002-6

1873-3956

Suchitra Sen, S. Thiagarajan,

Microwave Dielectric Ceramics Synthesis

Binary gels of SiO2-Al2O3 of different compositions were prepared, using alkoxides, by the sol-gel technique. In this communication, we report the preparation and phase-transformations of 3Al2O3-2SiO2 (mullite) gel. The material obtained was dried and heat-treated at different temperatures for dehydration-polymerization. Further heat-treatment above 900°C promoted crystallization, a metastable phase first being formed leading to the stable mullite phase. The kinetics and the microstructural evolution of these transformations were studied by X-ray diffraction, differential thermal analysis, electron microscopy, infrared spectroscopy and refractive index measurements. It was found that in this gel material the high-temperature heat-treatment at 1450°C produced pure well-crystallized mullite (particle size ∼ 0.07–0.15 μm) of prismatic shape contrary to its characteristic acicular habit.