Thermodynamic Examination of Quaternary Compounds in the Ag–Fe–(Ge, Sn)–Se Systems by the Solid-State EMF Method

Mykola Moroz*, Fiseha Tesfaye, Pavlo Demchenko, Myroslava Prokhorenko, Bohdan Rudyk, Lyudmyla Soliak, Daniel Lindberg, Oleksandr Reshetnyak, Leena Hupa

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionScientificpeer-review


The equilibrium phase space of the Ag–Fe–X–Se (X: Ge, Sn) systems in the parts Ag8XSe6–XSe–FeSe2–AgFeSe2–Ag8XSe6 consists of four quaternary-phase regions formed with the participation of low-temperature modifications of the Ag2FeGeSe4 and Ag2FeSnSe4 compounds. The kinetic barriers of the formation of equilibrium four-phase regions that are observed under conditions of vacuum ampoule synthesis below 600 K were overcome by synthesis of phases at the positive electrodes of electrochemical cells (ECCs): (−)C | Ag | SE | R (Ag+) | PE | C(+), where C is graphite, Ag is left (negative) electrode, SE is the solid-state electrolyte, PE is the right (positive) electrode, and R (Ag+) is the region of Ag+ diffusion into PE. Silver cations Ag+ that shifted from the left to the right electrode of ECCs acted as the seed centers of an equilibrium set of phases. Based on the temperature dependences of the EMF of the cells in the temperature range 430–485 K, the standard thermodynamic functions of the Ag2FeGeSe4 and Ag2FeSnSe4 compounds were calculated for the first time. The observed experimental results and thermodynamic calculations are in good agreement.

Original languageEnglish
Title of host publicationMaterials Processing Fundamentals 2021
EditorsJonghyun Lee, Samuel Wagstaff, Alexandra Anderson, Fiseha Tesfaye, Guillaume Lambotte, Antoine Allanore
Number of pages13
ISBN (Electronic)978-3-030-65253-1
Publication statusPublished - 2021
MoE publication typeA4 Article in a conference publication
EventMaterials Processing Fundamentals Symposium - Virtual, Online
Duration: 15 Mar 202118 Mar 2021

Publication series

NameMinerals, Metals and Materials Series
ISSN (Print)2367-1181
ISSN (Electronic)2367-1696


ConferenceMaterials Processing Fundamentals Symposium
CityVirtual, Online


  • EMF method
  • Gibbs energy
  • Magnetic semiconductors
  • Phase equilibria
  • Silver-based phases
  • Standard thermodynamic properties


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