Phase equilibria and structural investigations of the general NiAs-type in the ternary system Ni–Sn–Te

Abstract

The ternary system Ni–Sn–Te was investigated by means of light optical microscopy (LOM), powder X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) in combination with energy dispersive X-ray spectroscopy (EDX). Two isothermal sections at 600 and 800 °C were investigated experimentally. The two ternary compounds, Ni5.78SnTe2 (space group I4/mmm, Pearson symbol tI18) and Ni3−xSnTe2 (space group P63/mmc, Pearson symbol hP12), already known from literature, were confirmed, although Ni3−xSnTe2 was found only at 600 °C. At higher temperatures a continuous phase field of the general NiAs-type structure was discovered between NiTe2−x and Ni3Sn2 HT. It ranges continuously from 34 to 63 at.% Ni, covering CdI2-types, as well as Ni2In-type domains; thus a continuous transition from the CdI2 to Ni2In type is confirmed, to the best of our knowledge, for the first time. Lattice parameter variations and the transition CdI2–NiAs–Ni2In in the ternary phase field were analysed.Furthermore, vertical sections at 10, 40, 55, 60 and 70 at.% Ni were determined. A liquidus surface projection and a reaction scheme of the system were constructed as well. Altogether, 17 invariant phase reactions, including 3 eutectic reactions, 2 peritectic reactions, 11 transition reactions and one maximum were discovered.