Phase equilibria in the Ag–Ge–Bi–Te system and thermodynamic properties of the nGeTe×mBi2Te3 (n, m = 1-4) layered compounds

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

*Corresponding author for this work

Research output: Chapter in Book/Conference proceedingChapterScientificpeer-review


Phase equilibria of the Ag–Ge–Bi–Te system in the part GeTe–Ag8GeTe6–Te–Bi2Te3 (I) were established by the electromotive force (EMF) method with a solid Ag+ conducting electrolyte. It was shown that the concentration space of (I) in the part 4GeTe-Bi2Te3–Ag8GeTe6–Te–Bi2Te consists of 8 four-phase regions, formed of the layered compounds of the nGeTe.mBi2Te3 (n, m = 1-4) homologous range, as well as Ag8GeTe6, Bi2Te3, and Te. Equations of overall potential-forming reaction of the decomposition and synthesis of compounds of the homologous range were written for each region. Reactions were performed in the following electrochemical cells (ECCs) (−)IE | Ag | SE | PE | IE(+), where IE is the inert electrode (graphite), Ag is the negative (left) electrode, SE is the solid-state Ag+ ion-conducting electrolyte, PE is the positive (right) electrode. PEs of ECCs were prepared by melting of a mixture of the high-purity elements Ag, Ge, Bi, and Te. The component ratios in samples were determined based on the equations of the potential-forming reactions in respective phase regions. The finely grounded samples were used as PEs of ECCs. The synthesis of an equilibrium set of phases was performed in the part of PE that is in contact with SE of ECC at Т = 580 K for 50 h. Silver cations that shift from the left to the right electrode acted as the nucleation centers of equilibrium compounds in the corresponding phase regions. Linear dependences Е vs Т of ECCs in the range of Т = (440–500) K were used to calculate values of the Gibbs energies, enthalpies of formation, and entropies of compounds GeTe.4Bi2Te3, GeTe.3Bi2Te3, GeTe.2.5Bi2Te3, GeTe.2Bi2Te3, GeTe.Bi2Te3, 2GeTe.Bi2Te3, 3GeTe.Bi2Te3, and 4GeTe.Bi2Te3. The differences in the values of the thermodynamic functions of GeTe-rich and Bi2Te3-rich compounds with respect to GeTe.Bi2Te3 correlate well with the literature data on the differences of their crystal structures.
Original languageEnglish
Title of host publicationTMS 2022 151st Annual Meeting & Exhibition Supplemental Proceedings
Place of PublicationSwitzerland AG
PublisherSpringer International Publishing
Number of pages9
Publication statusPublished - 2022
MoE publication typeA3 Part of a book or another research book
EventTMS 2022 Annual Meeting & Exhibition - Anaheim Convention Center & Anaheim Marriott , Anaheim, United States
Duration: 27 Feb 20223 Mar 2022
Conference number: 151

Publication series

Name The Minerals, Metals & Materials Series
PublisherSpringer Nature Switzerland AG
ISSN (Print)2367-1181


ConferenceTMS 2022 Annual Meeting & Exhibition
Abbreviated titleTMS2022
Country/TerritoryUnited States
Internet address


  • Layered Compounds
  • Phase equilibria
  • Thermodynamic properties
  • EMF method
  • Gibbs energy


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