The Se<inf>2</inf> (Gas) Fugacity in Systems with Noble Metals: Chrisstanleyite Ag<inf>2</inf>Pd<inf>3</inf>Se<inf>4</inf> – Naumannite Ag<inf>2</inf>Se–β-PdSe<inf>2</inf> and Luberoite Pt<inf>5</inf>Se<inf>4</inf>–Sudovikovite PtSe<inf>2</inf>

© 2019, Pleiades Publishing, Ltd. Abstract: The reactions of 6Ag(cr) + 3PdSe2(cr) = 2Ag2Se(cr) + Ag2Pd3Se4(cr) and 12Ag(cr) + 5PtSe2(cr) = 6Ag2Se(cr) + Pt5Se4(cr) were studied with the EMF method in a completely solid-state galvanic cell with an Ag ion-conducting solid electrolyte with overall gas space (argon under atmospheric pressure). The EMF vs. temperature dependencies were obtained in the temperature ranges of Т = 425–648 K and 501–713 K, respectively. Then, they were recalculated for gaseous Se fugacity in dependence on the temperature for nonvariant equilibriums of Ag2Pd3Se4 (chrisstanleyite)–β-PdSe2 (the phase, which transforms into verbeekite under low temperatures)–Ag2Se (naumannite) and Pt5Se4 (luberoite)–PtSe2 (sudovikovite): logf Se2(gas) (Ag2Pd3Se4/Ag2Se/PdSe2) = 7.710 ± 0.050 – 8.524 ± 0.026(1000/T), logfSe2(gas) (Pt5Se4/PtSe2) = 7.135 ± 0.027 – 12.274 ± 0.016(1000/T)