Formation and stability of ternary phases in the Ho–Ag–Sn and Tm–Ag–Sn metallic systems

Chem. Met. Alloys 9 (2016) 135-146

https://doi.org/10.30970/cma9.0343

L. ROMAKA, I. ROMANIV, V.V. ROMAKA, A. HORYN, Yu. STADNYK

The isothermal sections of the phase diagram of the Ho–Ag–Sn ternary system at 673 K and 873 K were constructed in the whole concentration range using X-ray diffraction and EPM analyses. The interaction between the elements results in the formation of three ternary compounds at 673 K: HoAgSn (LiGaGe-type, space group P6₃mc, a = 0.4667(1), c = 0.7313(2) nm), Ho₃Ag₄Sn₄ (Gd₃Cu₄Ge₄-type, space group Immm, a = 0.4519(2), b = 0.7280(3), c = 1.5091(3) nm), and HoAgSn₂ (Cu₃Au-type, space group Pm-3m, a = 0.4525(2) nm). At 873 K two ternary compounds (HoAgSn, LiGaGe-type and HoAgSn₂, Cu₃Au-type) were found. Three ternary compounds exist in the Tm–Ag–Sn system at 873 K: TmAgSn (ZrNiAl-type, space group P-62m, a = 0.72635(9), c = 0.4435(1) nm), Tm(Ag,Sn)₂ (CaIn₂-type, space group P6₃/mmc, a = 0.46534(2), c = 0.72649(4) nm) and TmAgSn₂ (Cu₃Au-type, space group Pm-3m, a = 0.45033(2) nm). DSC/DTA analyses showed a limited stability range for Ho₃Ag₄Sn₄ and the existence of a phase transition for the TmAgSn compound. DFT calculations predict metallic-like behavior for both HoAgSn₂ and Ho₃Ag₄Sn₄.

The distribution of the electron localization function (ELF) in Ho₃Ag₄Sn₄.

Keywords

Intermetallics / Electronic structure / Diffraction / Differential scanning calorimetry