The Equilibrium Phase Formation and Thermodynamic Properties of Functional Tellurides in the Ag–Fe–Ge–Te System

Mykola Moroz, Fiseha Tesfaye, Pavlo Demchenko, Myroslava Prokhorenko, Nataliya Yarema, Daniel Lindberg, Oleksandr Reshetnyak and Leena Hupa
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Mykola Moroz: Department of Chemistry and Physics, National University of Water and Environmental Engineering, 33028 Rivne, Ukraine
Fiseha Tesfaye: Johan Gadolin Process Chemistry Centre, Åbo Akademi University, 20500 Turku, Finland
Pavlo Demchenko: Department of Inorganic Chemistry, Ivan Franko National University of Lviv, 79005 Lviv, Ukraine
Myroslava Prokhorenko: Department of Cartography and Geospatial Modeling, Lviv Polytechnic National University, 79013 Lviv, Ukraine
Nataliya Yarema: Department of Cartography and Geospatial Modeling, Lviv Polytechnic National University, 79013 Lviv, Ukraine
Daniel Lindberg: Department of Chemical and Metallurgical Engineering, Aalto University, Kemistintie 1, 02150 Espoo, Finland
Oleksandr Reshetnyak: Department of Physical and Colloid Chemistry, Ivan Franko National University of Lviv, 79005 Lviv, Ukraine
Leena Hupa: Johan Gadolin Process Chemistry Centre, Åbo Akademi University, 20500 Turku, Finland

Energies, 2021, vol. 14, issue 5, 1-15

Abstract: Equilibrium phase formations below 600 K in the parts Ag 2 Te–FeTe 2 –F 1.12 Te–Ag 2 Te and Ag 8 GeTe 6 –GeTe–FeTe 2 –AgFeTe 2 –Ag 8 GeTe 6 of the Fe–Ag–Ge–Te system were established by the electromotive force (EMF) method. The positions of 3- and 4-phase regions relative to the composition of silver were applied to express the potential reactions involving the AgFeTe 2 , Ag 2 FeTe 2 , and Ag 2 FeGeTe 4 compounds. The equilibrium synthesis of the set of phases was performed inside positive electrodes (PE) of the electrochemical cells: (−)Graphite ‖LE‖ Fast Ag + conducting solid-electrolyte ‖R[Ag + ]‖PE‖ Graphite(+), where LE is the left (negative) electrode, and R[Ag + ] is the buffer region for the diffusion of Ag + ions into the PE. From the observed results, thermodynamic quantities of AgFeTe 2 , Ag 2 FeTe 2 , and Ag 2 FeGeTe 4 were experimentally determined for the first time. The reliability of the division of the Ag 2 Te–FeTe 2 –F 1.12 Te–Ag 2 Te and Ag 8 GeTe 6 –GeTe–FeTe 2 –AgFeTe 2 –Ag 8 GeTe 6 phase regions was confirmed by the calculated thermodynamic quantities of AgFeTe 2 , Ag 2 FeTe 2 , and Ag 2 FeGeTe 4 in equilibrium with phases in the adjacent phase regions. Particularly, the calculated Gibbs energies of Ag 2 FeGeTe 4 in two different adjacent 4-phase regions are consistent, which also indicates that it has stoichiometric composition.

Keywords: silver-based compounds; thermoelectric materials; phase equilibria; thermodynamic properties; Gibbs energy; EMF method (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (1)

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