ABSTRACT
Differential thermal analysis (DTA) has been applied to study the homogeneneity regions of I-II-VI2 and II-IV-V2 chalcopyrites such as CuInS2 (roquesite) and ZnGeP2. They sensitively changed their thermal behaviour adding small amounts of elemental or binary constituents to stoichiometric material. ZnGeP2 showed a congruent melting behaviour (mp = 1035(±3)°C) but did not exhibit solid-solid phase transitions as reported for other chalcopyrites. The homogeneity region was smaller than 0.25mole %. CuInS2 exhibited a nearly congruent melting point at 1093(±3)°C. The maximum of the liquidus at 1100(±3)°C of the join CuS - InS was shifted by 1–1.5 mole% to the CuS-side. DTA peak intensities related to latent heat of solid-solid phase transformations at 980(±3)°C and 1047(±3)°C were significantly attenuated by adding 2 mole% copper or indium sulfides to the ternary. At temperatures in the range from 500 to 680°C missing transformation points of the binaries CuS and InS indicated the boundaries of the homogeneity region which can extend to both sides of roquesite up to 1.5 mole% InS. At room temperature the homogeneity of roquesite ranges from ≤ 0.25mole% InS to 1.5mole% CuS.
