Thermochemical investigations in the tin–phosphorus system*

Abstract

Abstract Phosphorus vapor pressures were measured over tin–phosphorus samples using two independent experimental techniques. Using an isopiestic method, data points were obtained between approximately 0 and 71 at.% P in the temperature interval from 618 to 998 K. Vapor pressures were also measured at lower temperatures over two twophase fields, i. e. in (L + Sn4P3) between 559 and 677 K and in (Sn4P3 + Sn3P4) between 552 and 621 K, by a Knudsen cell based mass loss technique. Based on these measurements partial thermodynamic properties and integral Gibbs energies were derived. The composition dependence of the phosphorus activity was also derived for three selected temperatures, 650, 700, and 750 K. Standard molar Gibbs energies of formation of Sn4P3, Sn3P4 and SnP3 were determined and are given by: Δ f G m ° ( Sn 4 P 3 ) ( s ) ± 1.1 / kJ ⋅ mol − 1 = − 166.5 + 0.2007 T / K ( T = 559 − 794 K ) Δ f G m ° ( Sn 3 P 4 ) ( s ) ± 1.8 / kJ ⋅ mol − 1 = − 234.4 + 0.3053 T / K ( T = 552 − 705 K ) Δ f G m ° ( SnP 3 ) ( s ) / kJ ⋅ mol − 1 = − 113.0 + 0.1523 T / K ( T = 632 − 659 K )