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

Abstract

The ternary alloy system Ni–Pt–Sn was investigated in detail, with special focus on the general NiAs-type phases. Phase diagram and crystallographic parameters were analysed 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 550 and 700°C, respectively, were studied experimentally. In both of them a continuous phase field of the general NiAs type structure was detected between PtSn and Ni3Sn2 (high temperature modification), covering a continuous transition from the NiAs- to the Ni2In-type. Lattice parameter variation and occupation of the atomic positions throughout this phase field were analysed and partial ordering of the transition metals was discovered.Furthermore, seven vertical sections were determined at 15at.% Sn, 20at.% Sn, 50at.% Sn and 65at.% Sn, and diagonal series from Pt60Sn40–Ni70Sn30, Pt42Sn58–Ni60Sn40 and Pt41.7Sn58.3–Ni48.1Sn51.9. According to these sections, eight ternary invariant phase reactions were determined: five transition reactions, one eutectic reaction, one peritectoid reaction and a maximum. Moreover, a liquidus surface projection and a complete reaction scheme of the system were constructed.