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

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 th ree 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–S n 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 f or Ho3Ag4Sn4 and the existence of a phase transition for the TmAgSn compound. DFT calculations predict metal lic-like behavior for both HoAgSn2 and Ho3Ag4Sn4.