| Summary: | The oxidation reactions of BaLaCuS<sub>3</sub> in the artificial air atmosphere were studied at different heating rates in the temperature range of 50–1200 °C. The oxidation stages were determined by DSC-TG, XRD and IR–vis methods. The kinetic characteristics of the proceeding reactions were obtained with the use of the Kissinger model in a linearized form. Compound BaLaCuS<sub>3</sub> was stable in the air up to 280 °C. Upon further heating up to 1200 °C, this complex sulfide underwent three main oxidation stages. The first stage is the formation of BaSO<sub>4</sub> and CuLaS<sub>2</sub>. The second stage is the oxidation of CuLaS<sub>2</sub> to La<sub>2</sub>O<sub>2</sub>SO<sub>4</sub> and copper oxides. The third stage is the destruction of La<sub>2</sub>O<sub>2</sub>SO<sub>4</sub>. The final result of the high-temperature treatment in the artificial air atmosphere was a mixture of barium sulfate, copper (II) oxide and La<sub>2</sub>CuO<sub>4</sub>. The mechanism and stages of BaLaCuS<sub>3</sub> oxidation and further interactions of the components were discussed.
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