Phase Equilibria in the Ag2Te-PbTe-Sb2Te3 System and Thermodynamic Properties of the (2PbTe)1-x(AgSbTe2)x Solid Solutions

Leyla Farhad Mashadiyeva,Shabnam Hamlet Mansimova,Dilqam Babir Tagiyev,Mahammad Baba Babanly,Dunya Mahammad Babanly,Yusif Amirali Yusibov

doi:10.17344/acsi.2019.5748

Abstract

Phase equilibria in the Ag2Te-PbTe-Sb2Te3 system were experimentally investigated by means of differential thermal analysis, powder X-ray diffraction techniques and electromotive force (EMF) measurement method. A liquidus surface projection of the system, 750 K and 300 K isothermal sections, as well as five vertical sections of the phase diagram, were constructed. The primary crystallization fields of phases and homogeneity range of phases were also determined. The character and temperature of the various nonvariant and monovariant equilibria were identified. The studied sys-tem is characterized by the formation of a wide continuous band of a high-temperature cubic structured solid solution (?-phase) between PbTe and Ag1-xSb1 + xTe2 + x intermediate phase. The partial molar thermodynamic functions of lead telluride in alloys and standard integral thermodynamic functions of the ?-solid solutions along the 2PbTe-AgSbTe2 section were calculated based on the EMF measurements results.

Highlights

Alloys formed in Ag2X-AIVX-BV2X3 systems are good thermoelectric materials with a high thermoelectric figure of merit ZT.[6,7,8,9,10]
We report the thermodynamic properties of the (2PbTe)1–x(AgSbTe2)x solid solution formed in the system
Further investigations of the Ag-Sb-Te ternary system confirmed that this phase is only stable in a limited temperature range (633 K < T < 847 K) and it decomposes into solid solutions based on starting Sb2Te3 and IT-Ag2Te compounds below 633 K.41–43

Summary

Introduction

Complex silver-containing chalcogenides are among the advanced functional materials.[1,2,3] Thanks to the mobility of silver ions, these phases have mixed ion-electron conductivity and can be widely used in semiconductors, electrochemical energy storage materials, electrodes of fuel cells and batteries, etc.[4,5]. Alloys formed in Ag2X-AIVX-BV2X3 systems (where AIV = Ge, Sn, Pb; BV = Sb, Bi; X = S, Se, Te) are good thermoelectric materials with a high thermoelectric figure of merit ZT.[6,7,8,9,10] Besides, phases AIVBV2X4, AIVBV4X7, etc. Earlier we report the self-consistent phase equilibria description and thermodynamic study result in such silver-based multi-component telluride systems. Ag2Te-PbTe-Bi2Te3,25 Ag2Te-SnTe-Bi2Te3,26 and Ag2TeSnTe-Sb2Te3.27,28 In all these studied systems, high-temperature solid solutions with a cubic structure along the AIVТе-AgBV2Те3 section are formed

Literature Review

Experimental Part

Results and Discussion

Conclusıon

A pplications of Chalcogenides