Effects of Ag on phase transformation of Cu3Sb at high temperatures

Effects of Ag on the phase transformation of Cu3Sb were investigated through scanning electron microscopy, energy-dispersive X-ray spectroscopy, and high-temperature X-ray diffraction (XRD) measurements. Observations of Cu-Sb-Ag alloys following heat treatment at 500 degrees C revealed that Ag dissolved up to 11 at.% in a cubic beta-Cu3Sb phase stable only at high temperatures. XRD measurements confirmed that while a transformation from the beta-Cu3Sb phase to orthorhombic epsilon-Cu3Sb phase occurred at 440 degrees C in the binary system, the transformation occurred below 380 degrees C in the alloy containing 5% Ag, suggesting the enhanced stability of the beta-Cu3Sb phase owing to Ag. Furthermore, during measurements above 420 degrees C on alloys with a composition consistent with that of Cu3-xAgxSb containing 8-14% Ag (i.e., x = 0.32-0.56), the formation of a new alloy phase with a hexagonal structure (a = 4.3416 angstrom and c = 7.6864 angstrom at 500 degrees C) was observed. The crystal structure of the new alloy phase was inferred to be of the Na3As type, which belongs to the space group P6(3)/mmc. Based on observations of alloys with various compositions, an isothermal section of the Cu-Sb-Ag ternary phase diagram at 500 degrees C was constructed.

Automated summary

The effects of Ag on the phase transformation of Cu3Sb were investigated. It was found that Ag dissolved in the Cu3Sb phase, enhancing its stability. A new alloy phase with a hexagonal structure was also observed. The isothermal section of the Cu-Sb-Ag ternary phase diagram at 500 degrees C was successfully constructed based on observations of alloys with various compositions.