The thermal decomposition of pure and doped cadium carbonate: I. Kinetics

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Abstract
The thermal decomposition of both pure and doped cadmium carbonate has been studied. Doping was effected by adding 1, 5 and 10 atom‐% of Al3+, Li+, Zn2+, Ca2+, and Ba2+. Differential thermal analysis, as well as the kinetics of isothermal decomposition of the various carbonates, has been investigated between 310 and 560 °C. The decomposition of both the pure and doped samples was found to obey Mampel's theory. Rate constants were evaluated and found to be appreciably affected by the presence of foreign ions. Application of the Arrhenius equation gave an activation energy of 22.5 kcal/mol for pure cadmium carbonate which is comparable with the standard enthalpy of the reaction which is 22.0 kcal/mol. On the other hand, in applying the Arrhenius equation to the rate constant of the doped samples, no straight lines could be obtained indicating a continuous decrease in the activation energy with a rise of temperature. The activation energies were found to vary between 4.0 and 44.0 kcal/mol. Discussion is presented to account for the effect of the various dopes on the mechanism of thermal decomposition.

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