A study of the thermal decomposition of BaCO3

In the present work, the decomposition reaction, BaCO3 (solid) = BaO (solid) + CO2 (gas), was investigated by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) methods. Both shallow powder beds and densely compacted spheres of the carbonate were employed, In the case of the shallow powder beds, TGA and DTA were carried out simultaneously. The DTA curves showed that BaCO3 exhibited two phase transformations, the transformation of orthorhombic to hexagonal occurring at 1079 K and that of hexagonal to cubic at 1237 K. The activation energy and the forward reaction rate constant of the decomposition of BaCO3 were evaluated from the thermogravimetric results of the powder beds. The activation energy of the decomposition was found to be 305(+/- 14) KJ . mole(-1). The experimental results obtained with the compacted spheres were compared with those corresponding to the powder beds. After the initial stages, the formation of liquid due to the eutectic reaction between BaCO3 and BaO appears to play an important role in the reaction kinetics.