The thermal decomposition of FeS2 and BaO2 mixtures (mol ratio from 2 to 8) was studied in oxygen containing gas medium using dynamic heating rate. The solid decomposition
products have been investigated with X-ray power diffraction and Mssbauer spectrometer. The thermal process has two main
stages. In the presence of BaO2 the mixtures have a lower initial temperature of iron sulfide burning. The same time by the increasing of BaO2 content in the mixtures the diffusion difficulties are withdrawn in higher temperature ranges. It is proved that as intermediates
BaSO4, nonstoichiometric sulfide, barium ferrites and Fe2O3 are formed. The content of many solid phases in the final product is in relationship with the initial ratio of BaO2 and FeS2.