Effects of various atmospheres and some metal oxide additives on the thermal decomposition on ammonium chromate

The thermal decomposition of ammonium chromate (AC) in dynamic air, CO₂ and N₂ and in static atmospheres and in the presence of MoO₃, V₂O₅, Fe₂O₃, CuO, MnO₂ and Nd₂O₃ additives was studied by means of TG, DTA, IR spectroscopy and electrical conductivity measurements. It was found that AC decomposes in four stages, forming unstable intermediates which produce Cr₂O₃ as a final product. The presence of the different atmospheres and the oxide additives affected the decompositions of these intermediates and the oxidation state of the chromium ions. Finally, the mechanisms associated with the different decomposition stages are discussed.