Effect of precompression on isothermal decomposition kinetics of pure and doped potassium bromate

Pure and doped samples of potassium bromate (KBrO3) were subjected to precompression and their thermal decomposition kinetics was studied by thermogravimetry at 668 K. The samples decomposed in two stages governed by the same rate law (contracting square equation), but with different rate constants, k1 (for a α ≤ 0.45) and k2 (for α ≥ 0.45), as in the case of uncompressed samples. The rate constants k1 and k2 decreased dramatically on precompression, the decrease being higher for doped samples. Cation dopants (Ba2+, Al3+) caused more desensitization effect than the anion dopants (\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ {\text{SO}}_{4}{}^{ 2- } $$\end{document}, PO43−) of the same magnitude of charge and concentration. The results favor ionic diffusion mechanism proposed earlier on the basis of doping studies.