Experimental Thermodynamic Characterization of the Chalcopyrite-Based Compounds in the Ag–In–Te System for a Potential Thermoelectric Application

The equilibrium concentration space of the Ag–In–Te system in part AgInTe2–Te–In2Te3 was studied through modified solid-state electromotive force (EMF) method by dividing In2Te3–In2Te5–Ag3In97Te147 (I), In2Te5–Te–Ag3In97Te147 (II), Ag3In97Te147–Te–AgIn5Te8 (III), AgIn5Te8–Te–AgIn3Te5 (IV), and AgIn3Te5–Te–AgInTe2 (V), into separate phase regions at T ≤ 500 K. formation a thermodynamically stable combination binary ternary phases (I)–(V) from metastable mixture substances carried out K R(Ag+) positive electrode (PE) galvanic cells (GCs) structure: (−) C |∙| Ag SE PE (+), where is graphite (inert electrode), electrolyte (Ag3GeS3Br glass), left (negative) electrode. Ag+ ions region functioned as small nucleation centers for phases. spatial position relative to silver used express overall potential-forming reactions with participation Ag, Te, In2Te5, Ag3In97Te147, AgIn5Te8, AgIn3Te5, AgInTe2. subsequent EMF measurements were applying same GCs. temperature dependences GCs here determine, first time, values standard thermodynamic functions compounds. determined Gibbs energies compounds are equal: GIn2Te5○=(182.7±1.9) kJ·mol−1, GAgInTe2○=(115.0±3.1) GAgIn3Te5○=(301.5±6.5) GAgIn5Te8○=(487.6±11.3) GAg3In97Te147○=(8594±189) kJ·mol−1 correctness division involving AgInTe2, Ag3In97Te147 confirmed agreement calculated literature-based data In2Te5 compound. Compositions pairs their practical application proposed.