Decomposition of a Synthetic Copper Sulfoarsenide

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We have studied the thermal behavior of synthetic lautite, a copper sulfoarsenide widespread in nature. The material was characterized by thermogravimetric analysis under nonisothermal and isothermal conditions. Using the data thus obtained, equations of nonisothermal formal kinetics, and the Kazeev–Erofeev–Kolmogorov equation with the Sakovich correction, we assessed kinetic parameters. Lautite decomposition to copper sulfides has been shown to be accompanied by the formation of tennantite as an intermediate phase. The sublimates consist of an alloy of arsenic sulfides. The E_a values obtained under nonisothermal conditions suggest that synthetic CuAsS dissociation is a kinetically controlled process. The E_a values obtained under isothermal conditions suggest that, at a temperature of 500°C, the lautite decomposition process switches from intermediate to diffusion control.