Mechanism of thermal decomposition of irradiated and unirradiated KIO4 and X.R.D spectroscopy

The thermal decomposition of γ-ray irradiated KIO4 hase been studied. The decomposition isotherms present a saturation value at long heating times. Also a saturation value has been observed for the decomposition fraction as a function of the absorbed γ-ray dose. Kinetic analysis of the irradiated decomposition data shows a decrease in the dimensionality of the reaction ,n, from the Erofeev equation, compared with the unirradiated KIO4, (n is constant and equal 1.8 for the irradiated and varies between 2-3 for the unirradiated, the activation energy is about 1 eV). The effect of γ-ray was investigated and it was shown that all the isotherms reach the same value with diffrent γ-ray doses. X-ray diffraction of the KIO4 after taking off the outer part of crystal has been studied to determine the crystalography variation due to heating and irradiation. The analysis of this data shows a decrease of the surface area corresponsing to (hk1) plane as a function of the decomposition degree and γ-ray dose. This means that there is a variation of the concentration of atoms in (hk1) plane. The positron annihilation has been studied in order to obtain more informations about the defects, but the variation of its intensity is very small. 32 refs., 7 figs. (author)