Component Interaction in the Quasi-Ternary System PbSe–Ga2Se3–GeSe2

Liquidus surface projection of the quasi-ternary system PbSe–Ga 2 Se 3 –GeSe 2 and its isothermal section at 670 K (397 °C) were investigated over eight sections and separate alloys using DTA, XRD and microstructure analysis methods. The existence of the PbGa 2 GeSe 6 and Pb 4 Ga 4 GeSe 12 compounds was confirmed. Pb 4 Ga 4 GeSe 12 is shown to be a part of a large solid solution range of the new quaternary compound Pb 3 Ga 2 GeSe 8 (S.G. P –42 1 c ) that forms at the intersection of the sections PbGa 2 Se 4 –Pb 2 GeSe 4 and PbGa 2 GeSe 6 –PbSe. These quaternary phases triangulate the quasi-ternary system at 670 K (397 °C) into seven sub-systems and have significant solid solubility. The character and temperatures of mono- and invariant reactions were determined. Only three sections, Ga 2 Se 3 –PbGa 2 GeSe 6 , PbGa 2 GeSe 6 –PbSe, and PbGa 2 GeSe 6 –GeSe 2 , are quasi-binary. The PbGa 2 Se 4 –PbGa 2 GeSe 6 , PbGa 2 Se 4 –Pb 2 GeSe 4 and PbGa 2 GeSe 6 –Pb 2 GeSe 4 sections are quasi-binary only in the sub-solidus region due to the incongruent melting of PbGa 2 Se 4 and Pb 2 GeSe 4 . PbGa 2 GeSe 6 melts congruently at 960 K (687 °C) and has a phase transition at 795 K (522 °C); Pb 3 Ga 2 GeSe 8 forms incongruently at 929 K (656 °C) and has a phase transition at 851 K (578 °C).