The preparation of mullite coatings through chemical vapor deposition (CVD) from mixtures of silicon tetrachloride, aluminum trichloride, carbon dioxide, and hydrogen is addressed in this study. The results of past experimental studies on the kinetics of this deposition system and the predictions of a mathematical model that involves detailed homogeneous and heterogeneous chemistry mechanisms for the codeposition process are used to identify operating conditions where deposition of coatings consisting of mullite or alumina-rich mullite is possible. Deposition experiments are carried out in a hot-wall reactor using as substrates both small thin plates and refractory wires traversing the centerline of the reactor. Results are presented on the dependence of the film composition in silica and alumina on temperature, pressure, and residence time of the reactive mixture in the reactor. The results showed that the alumina content of the deposits increased towards the entrance of the reactor, exceeding in many cases the value that corresponds to stoichiometric mullite. The microstructure and surface morphology of the deposit depended strongly on the operating conditions. In general, the deposition of material having the composition of mullite (2SiO(2) . 3Al(2)O(3)) or alumina-rich mullite was found to be favored by low operating pressures, high Si : Al feed ratios, and low residence times in the CVD reactor. (C) 2002 Elsevier Science B.V. All rights reserved.