Influences of the controlled decomposition rate and controlled residual pressure on the thermal decomposition process of synthetic bayerite were investigated by applying a method of controlled rate evolved gas detection (CREGD). Comparing with the conventional process under linearly increasing temperature, the thermal decomposition process of the synthetic bayerite at a controlled decomposition rate (similar to10(-2) Mg min(-1)) under controlled residual pressure (similar to10(-3) Pa) was characterized by the lowered reaction temperature profile and small changes in the specific surface area of the sample during the course of reaction. Formation of an amorphous alumina as the decomposition product is another important result of the process control by the present CREGD. The amorphous alumina crystallizes to eta-Al2O3 at around 1100 K. It is worth noting that the characteristics of the reaction process under controlled rate conditions and the formation of amorphous alumina as the decomposition product are very similar to those of mechanochemically activated bayerite under conventional linear heating. (C) 2004 Elsevier B.V. All rights reserved.