Solid way synthesis of barium aluminate. Kinetic study of the formation of intermediate compounds

Abstract

Synthesis of barium aluminate BaAl 2O 4 (noted BA) by solid-solid reaction at 900°C between powdered reactants of barium carbonate and alumina in stoichiometric proportions has been studied. During the synthesis and under particular gaseous atmospheres, the aluminate BA reacts with the carbonate to form an intermediate product Ba 3Al 2O 6 (noted B 3A). When barium carbonate has completely disappeared, B 3A and remaining alumina lead to the barium aluminate BA. In the present study, new experiments at 900°C using pellets made of each reactant BaCO 3 and Al 2O 3 as starting materials are described. All the information collected from the experimental results agreed with those mentioned in literature and allowed us to propose mechanisms for this reaction synthesis. An explanation of the formation of intermediate aluminates is also attempted. The mechanisms described include two kinds of oxygen transfer, either in the solid state, or in the gaseous atmosphere. Kinetic developments corresponding to the most probable rate determining steps in each case are carried out and summarized. The importance of the various chemical parameters which modify the reaction process are discussed and the influence of the gaseous atmosphere is particularly followed.