Isothermal section of the phase diagram of the Tb–Lі–Sn system at 400 ºС

Abstract

The isothermal cross-section of phase diagram of Tb–Li–Sn system based on X-ray phase and local X-ray spectral analyses has been constructed at the temperature of 400 ºС in the range 30–100 аt. % Sn. The alloys were prepared by arc melting of stoichiometric amounts of the constituent elements, annealed at 400 ºС for 480 hours and quenched in cold water. The calculations and indexing powder diffraction have been conducted using LATCON and POWDER CELL-2.3 software. Calculations to refine the structure of samples have been carried out by with CSD and 98 FullProf. Two new ternary compounds have been synthesized for the first time: TbLiSn (structural type YLiSn, Pearson symbol hP24, space group P 6 3 mc , a = 0.9308(1), c = 0,7356(1) nm) and ~Tb 4 LiSn 4 (unknown structure). Existence of TbLiSn 2 ternary compound (structural type CeNiSi 2 ) and thirteen binary phases has been confirmed. Existence of the limited inclusion type solid solution based on Tb 5 Sn 3 binary compound Tb 5 Li x Sn 3 (0 ≤ х ≤ 1.0) has been detected. Ultimate composition of this solid solution is Tb 5 LiSn 3 (structural type Hf 5 CuSn 3 , Pearson symbol hP18 , space group P6 3 /mcm, a = 0,9012(1), c = 0,6574(1) nm). All these compounds have been refined using powder X-ray diffraction data (diffractometers DRON-2.0M (Fе К α-radiation), STOE STADI P (Cu Kα 1 -radiation) and URD-6 (Cu Kα-radiation)). Existence of TbLiSn 2 ternary compound (structural type CeNiSi 2 ) and binary phases Tb 5 Sn 3 , Tb 5 Sn 4 , Tb 11 Sn 10 , TbSn 2 , Tb 3 Sn 7 , TbSn 2,7 , Li 17 Sn 4 , Li 7 Sn 2 , Li 13 Sn 5 , Li 5 Sn 2 , Li 7 Sn 3 , LiSn and Li 2 Sn 5 has been confirmed. The characteristics of phase interactions in Tb–Li–Sn as well as related systems with rare-earth metals, Lithium and Tin have been analyzed. Keywords: Terbium, Lithium, Tin, ternary system, phase equlibria, synthesis, intermetallic compounds, crystal structure, solid solution.