• Blazevic, Amir
• Richter, Klaus W.
• Effenberger, Herta S.

Abstract

The ternary Au-Cu-Si system was investigated by means of powder X-ray diffraction (XRD) for phase identification, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) for microstructures and chemical compositions, light optical microscopy (LOM), and differential thermal analysis (DTA) for the determination of thermal effects. Three isothermal sections were constructed at 250 C, 400 C and 650 C. A new ternary compound τ, Au CuSi, was identified and its crystal structure was determined by means of single crystal X-ray diffraction. It adopts a new crystal structure type in space group Pnma, Pearson symbol oP32 and shows a composition range between AuCuSi and Au CuSi at 250 C. Lattice parameters were found to vary between a = 9.64-9.50 Å, b = 7.61-7.64 Å and c = 6.90-6.89 Å from the Au-rich to the Au-poor composition limit. Three vertical sections, at 10 and 30 at.% Si and at 10 at.% Cu, were constructed based on DTA data and four invariant ternary phase reactions were identified. A partial ternary reaction scheme (Scheil diagram) and a partial liquidus projection are given.

Topics

• compound
• single crystal X-ray diffraction
• single crystal
• phase
• scanning electron microscopy
• powder X-ray diffraction
• chemical composition
• Energy-dispersive X-ray spectroscopy
• optical microscopy
• differential thermal analysis
• space group