Partial Pressures in the Cd‐Te and Zn‐Te Systems

Partial pressures of Te₂ Cd, and Zn have been determined to within 10% for a number of compositions in the Cd‐Te and Zn‐Te systems by measuring the optical density of the vapor phase between 1990 and 7000Aå. For Te‐saturated , the partial pressure of Te₂, p₂ reaches a maximum value of 0.188 atm near 915°C. For Cd‐saturated , pcd is within a few per cent of that for pure Cd up to 840°C. At the 1092°C melting point, and . At 900°C the homogeneity range for is shown to lie within outer limits of 49.0 and 50.5 a/o (atom per cent) Tand ΔG_f varies by less than 150 cal/g‐atom between either Cd‐saturated or Te‐saturated and congruently subliming . Liquidus temperatures and the partial gramatomic enthalpy and entropy are obtained for 55.0, 60.0, and 65.0 a/o Te melts. The liquidus points confirm the presence of an inflection point in the Te‐rich liquidus and it is shown that this behavior is due primarily to the nonideal behavior of the Cd activity coefficient. Similarly , pZn for Zn‐saturated has been determined to 900°C and p2 for the Te‐saturated to 1080°C. The homogeneity range at 900°C is bracketed between outer limits of 49.5 and 50.5 a/o Te corresponding to a maximum variation of ΔG_f of 190 cal/g‐atom between either Zn‐saturated or Te‐saturated and congruently subliming .