Phase relations in the system PbS-PbSe-PbTe

Phase relations in the system P b S P b S e P b T e were investigated in the temperature range between 1150 and 300~ There is a complete solid solution series along the join PbS-PbSe, whereas miscibility gaps exist below ~ 350~ and 805~ along joins PbSe-PbTe and PbS-PbTe, respectively. Both gaps extend into the ternary system, and the range of the gap between PbS and PbTe reduces in size with temperature as well as Se-content. By using the subregular model of mixing (Ganguly and Saxena, 1987), mixing energetics and activitycomposition relations of PbX were derived. The temperature-dependence of the interaction parameters was calculated to be 5057.6 1.7T, 9605.2 4.4T, 3933.2 3.1T (T < 500~ 6410.3 6.35T (T < 500~ 1649 0.26T, 1594.6 0.2T, and 12906.3 17.3T for WsTe, Wves, Wsere, WT~S~, Wss~, WsCs, and WSSeT~, respectively. A critical temperature along the join PbS-PbSe at ~ 100~ was obtained from interaction parameter calculation, which suggests the separation of the PbS-PbSe series. Correlation of solid-solution ranges established in this study with natural occurrences was made. K~VWORDS: lead chalcogenides, phase relations, thermodynamics, P b S P b S e P b T e system.