Isothermal sections of Tm-Ag-Sn and Lu-Ag-Sn ternary systems at 873 K

Abstract

The isothermal sections of the Tm-Ag-Sn and Lu-Ag-Sn ternary systems at 873 K were constructed with use of scanning electron microscopy, energy dispersive X-ray microanalysis and powder diffraction. Existence of the ternary compounds TmAgSn and LuAgSn in the form of low-temperature (LT) polymorphs (ZrNiAl-type, P-62m, Z = 3) and TmAgSn2 (Cu3Au-type, Pm-3m, Z = 1) was confirmed. For the latter homogeneity region was established (TmAg1−xSn2+x, where 0.04 ≤ x ≤ 0.24) and lattice parameter dependence on composition was specified (a = 4.4814 + 0.1836x Å). Two new ternary phases which are metastable at 873 K were discovered: TmAg0.68Sn2.32 (CuFePt2-type, P4/mmm, a = 4.369(1) Å, c = 4.906(1) Å) и LuAg1−ySn2+y (where 0.28 ≤ y ≤ 0.40). Also existence of Lu11Sn10 was found but its crystal structure was not defined. For the binary compound Ag51Tm14 structure type was established (Ag51Gd14, P6/m) and lattice parameters (a = 12.5924(6), c = 9.1939(5)) determined.It was shown from temperature dependences of electrical resistivity and specific heat capacity that ternary phases TmAgSn2, LT-LuAgSn and HT-TmAgSn (high-temperature polymorph, LiGaGe-type, P63mc, Z = 2) do not undergo transition into the magnetically ordered state between 1.78 and 300 K. For LT-TmAgSn Neel temperature value of 4.2 K was confirmed.