Thermal Stability and Thermodynamics of the Ag2ZnGeS4 Compound
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Phase equilibria in the ZnS–Ag2GeS3–Ge–GeS2 part of the Ag–Zn–Ge–S system were investigated using differential thermal analysis, X-ray diffraction, and EMF methods. The data was used to model Ag2GeS3–ZnS polythermal section. Further, the mechanism of formation and thermal stability of the Ag2ZnGeS4 compound were established. The results suggest the presence of another quaternary phase Ag4ZnGe2S7 in the temperature range of 695–853 K. The determined phase relations were used to express the chemical reactions. Based on the electromotive force versus temperature measurements, experimental thermodynamic data of the Ag2ZnGeS4 quaternary phase were derived for the first time. The calculated Gibbs energy, enthalpy and entropy values of the Ag2ZnGeS4 compound in both phase regions are consistent, which indicates that Ag2ZnGeS4 has stoichiometric composition.
KeywordsChalcogenide semiconductors Phase equilibria Thermodynamic properties EMF method Gibbs energy
The authors are grateful to the Academy of Finland for financial support. This work was made under the project “Thermodynamic investigation of complex inorganic material systems for improved renewable energy and metals production processes” (Decision number 311537) as part of the activities of the Johan Gadolin Process Chemistry Centre at Åbo Akademi University. In addition, funding from the Academy of Finland project “Behavior and properties of molten ash in biomass and waste combustion” (Decision number 266384) for M. Moroz and D. Lindberg is greatly appreciated.
Conflict of Interest
The authors declare that they have no conflict of interest.
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