Phase subsolidus separation of the Ge–P–Sn ternary system

2D materials are becoming increasingly attractive for use in modern electronic devices due to new properties that can arise from reduced dimensionality and the quantum confinement of charge carriers. Many studies are aimed at the search for materials characterized by a layered structure, which allows obtaining chemically stable atomic layers without surface broken bonds. Binary compounds of elements of IV (Si, Ge, Sn) and V (P, As) groups form layered structures in which two-dimensional layers with covalent bonds are bound by weak van der Waals forces, and from this point of view they can be considered as being promising 2D materials. However, it should be noted, that obtaining crystals of compounds of this class is associated with significant difficulties due to the high vapor pressure of phosphorus. Attempts have been made to obtain the GeP samples from tin melt solutions, which can significantly soften the synthesis conditions. The study of phase equilibria and the construction of a phase diagram of the Ge–P–Sn ternary system would allow approaching the production of both bulk and two-dimensional samples of germanium phosphide, as well as determining the possibility of alloying them with tin. In this study, based on the investigation of several alloys of the Ge–P–Sn ternary system using the X-ray phase analysis, it was established that the phase subsolidus separation of the state diagram is carried out by the Sn4P3–Ge, Sn4P3–GeP, Sn3P4–GeP and SnP3–GeP sections. The composition of the alloys corresponded to the figurative points of the intersecting sections. A scheme of phase equilibria in the Ge–P–Sn system was proposed. This scheme assumes the existence of a nonvariant peritectic equilibrium L+Ge ↔ Sn4P3+GeP and eutectic processes L ↔ Ge+Sn+Sn4P3 and L ↔ Sn4P3+GeP+SnP3. The study of alloys using the differential thermal analysis method allowed determining the temperatures of these processes, equal to 795 K, 504 K, and 790 K, respectively. The T-x diagram of the Sn–GeP polythermal cross section, which experimentally confirms the proposed scheme, was constructed