Phase diagram of the Sn–P system

The T–x diagram of the Sn–P system was studied by differential thermal analysis, X-ray phase analysis and local X-ray spectral microanalysis. An optical tensimetric method was used to evaluate the saturated vapor pressure of phosphorus. The method consists of in situ scanning of electronic absorption spectra of steam at different temperatures in order to obtain quantitative information about the vapor phase. In the concentration range 43–70 mol% P of the system investigated, a single eutectic equilibrium with participation of higher tin phosphides was found: L ↔ Sn₄P₃ + SnP₃. The Sn₃P₄ intermediate phase is formed only during prolonged annealing of the samples at a temperature of less than 623 K. A P–T–x diagram of the Sn–P system was constructed by a combination of differential thermal analysis and optical tensimetric methods. The coordinates of the four-phase equilibrium points were found: for the synthetics equilibrium Sn₄P₃ ↔ V + L₁ + L₂, the vapor pressure is 0.6 atm at 838 ± 2 K; for the eutectic equilibrium L ↔ V + Sn₄P₃ + SnP₃ 2.8 atm.