Solid-state decomposition studies on fluoroperoxo species of transition metals: Part XIII. Kinetics of isothermal decomposition of K 2[V 2O 3(O 2)F 2] and K 3[Ta(O 2) 2F 4

Abstract

Listen

Translate article

The kinetics of isothermal decomposition of K 2[V 2O 3(O 2) 2] and K 3[Ta(O 2) 2F 4] have been investigated in the temperature range 413–493 K using a constant volume apparatus. The α vs. time plots for both these solids are sigmoidal in nature. The kinetics obey the Avrami-Erofeev equation ( n = 2) for the initial stage of the decomposition. The contracting volume equation fits well for the deceleratory region. The activation energies are 164.8 and 105.4 kJ mol −1 for K 2[V 2O 3(O 2) 2F 2], and 85.2 and 76.6 kJ mol −1 for K 3[Ta.(O 2) 2F 4]. The absence of lattice water in these two solids may be responsible for the appearance of a short induction, followed by an acceleratory region in pristine solids, in contrast to hydrated fluoroperoxo zirconates, wherein the dehydration step preceding peroxide decomposition leads to facile nucleation and a deceleratory nature of decomposition. The kinetic characteristics of the decomposition of fluoroperoxo species so far studied are summarized and discussed.