Catalytic effects of lanthanide oxides on the thermal decomposition of barium perchlorate

Catalytic activities exerted by the lanthanide oxides Ln(2)O(3) (Ln=La, Sm, Gd and Dy) (0.25 mol%) on the thermal decomposition of barium perchlorate were studied gasometrically at 718 K. The alpha vs. t plot for the salt alone displays (i) initial gas evolution (ii) an induction period, (iii) a short acceleratory stage and (iv) a long decay stage. For the mixtures with Ln(2)O(3), phenomena (i) and (ii) are not observed. Ln(2)O(3) enhances the rate of reaction in both the acceleratory and the decay stage, and increases the fraction decomposed, alpha, in the sequence La2O3> Gd2O3> Sm2O3,> Dy2O3. The influence of Dy2O3 (0.25-2.0 mol%) on the decomposition of Ba(ClO4)(2) at 718 K indicates that such admixture facilitates the process and the effect increases with increasing concentration. The salt alone and the mixtures decompose through the same stages in the temperature range 703-733 K as at 718 K. The data on both types of samples fit well to the Prout-Tompkins and the Avrami-Erofeev mechanism, suggesting that nucleation takes place in a chain-branching manner and that the two-dimensional growth of the nuclei occurs during the process. Admixture enhances the rate of reaction marked without affecting the energy of activation.