Synthesis, X-ray data, and thermodynamic properties of the AgTe3 high-pressure phase in the Ag–Te system

Abstract

Silver telluride, AgTe3, was synthesized in a high-pressure gas vessel at a temperature of 473 K and a hydrostatic pressure of pure Ag at 6500 bar. A Rietveld structure refinement of X-ray powder diffraction data has been performed. The structure has been refined in the trigonal space group, R3m(H), and has the following cell parameters: a = 8.653 Å, c = 5.278 Å, and V = 342.24 Å3. It was found that AgTe3 stored in a sealed container for three months partially decomposes into Ag5Te3 (stützite) and tellurium.The thermodynamic properties of AgTe3 have been determined for the first time. The electromotive force (EMF) method for a solid-state galvanic cell with RbAg4I5 solid electrolyte.(−) Pt | Ag | RbAg4I5 | AgTe3, Te | Pt (+).was used to study a virtual chemical reaction of silver telluride formation from the elements;Ag(s) + 3Te(s) = AgTe3(s)The measurements were carried out in the temperature range of 402–474 K and pressures of 3921–6169 bar. The standard Gibbs energy of AgTe3 formation and its standard thermodynamic properties and molar volume at 298 K and 1 bar (105 Pa) pressure were derived from the EMF measurements:ΔrG(T, p)/J mol−1 = (−21470 ± 3880) + (133.0 ± 62.5)∙T – (21.96 ± 8.82)∙Tln(T).– (0.178 ± 0.009)∙(p – 1).ΔfG° (298.15 K, 1 bar) = −19.12 ± 0.24 kJ/mol; ΔfH° (298.15 K, 1 bar) = −14.92 ± 1.25 kJ/mol.S° (298.15 K, 1 bar) = 205.8 ± 3.5 J/(mol K).V° (298.15 K, 1 bar) = 69.93 ± 0.09 cm3/mol.