Thermal Analyses of Silver-Based Sulfosalts in Air

  • Fiseha TesfayeEmail author
  • Daniel Lindberg
Conference paper
Part of the The Minerals, Metals & Materials Series book series (MMMS)


The sulfosalts Ag0.93Cu1.07S (stromeyerite) and α-AgBiS2 (schapbachite) have been studied under oxidizing conditions at elevated temperatures. The sulfosalts were synthesized from the pure simple sulfides in evacuated quartz ampoules. The synthesized samples were thermally analyzed in the temperature range from 298 to 1173 K by a simultaneous DTA-TGA analyzer. Based on the DTA measurements the phase transition of stromeyerite to the solid solution (Cu, Ag)2S(hcp) in air is determined to be T = (360.9 ± 2) K. For the first time, maximum thermal stability of (Ag, Cu)2S in an oxidizing atmosphere close to the partial pressure of oxygen in air (P(O2) ≈ 0.20 atm) is determined to be below T = (614 ± 2) K, above which it oxidizes to form Ag, CuO and Ag2SO4. The melting temperature of Ag2SO4 determined from the cooling DTA curve, T = (932.76 ± 2) K, is in good agreement with the literature value. Below T = 1173 K, the oxidation process for schapbachite in air has been indirectly determined to be: 2AgBiS2 + 5.5O2(g) ⇄ 2Ag + Bi2O3 + 4SO2(g).


Silver Sulfosalts Thermal stability Oxidation DTA-TGA analysis Pyrometallurgical roasting 



The authors are grateful to the Academy of Finland for financial support. This work was made under the project “Chemistry of biomass impurities at reducing conditions in future thermal conversion concepts” as part of the activities of the Johan Gadolin Process Chemistry Center at Åbo Akademi University.


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© The Minerals, Metals & Materials Society 2017

Authors and Affiliations

  1. 1.Johan Gadolin Process Chemistry CentreÅbo Akademi UniversityTurkuFinland

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