The ternary system Zr–Al–Sn: isothermal section of the phase diagram at 600°C and crystal structures of the compounds

Chem. Met. Alloys 15 (2022) 1-7

https://doi.org/10.30970/cma15.0421

Danylo MARYSKEVYCH, Yaroslav TOKAYCHUK, Roman GLADYSHEVSKII

The isothermal section at 600°C of the phase diagram of the ternary system Zr–Al–Sn was constructed in the whole concentration range, using X-ray powder diffraction and energy-dispersive X-ray spectroscopy. Limited solid solutions of the substitution type, based on the binary compounds Zr₅Sn₄ (11.1 at.% Al) and Zr₅Sn₃ (2.5 at.% Al), were observed. The crystal structure of Zr₅AlSn₃ (boundary composition of the solid solution Zr₅Al_xSn_4-x) belongs to the structure type Hf₅CuSn₃ (Pearson symbol hP18, space group P6₃/mcm, a = 8.6184(19), c = 5.8656(14) Å), which is a ternary variant of the structure type Ti₅Ga₄. Three ternary compounds exist at 600°C: ZrAl_2.682(4)Sn_0.318(4) (structure type TiAl₃, tI8, I4/mmm, a = 3.98855(18), с = 9.0848(4) Å), Zr₅Al_2.71(1)Sn_0.29(1) (structure type W₅Si₃, tI32, I4/mcm, a = 11.0530(9), c = 5.4071(5) Å), and Zr₅Al_{1.68(3)-0.40(1)}Sn_{1.32(3)-2.60(1)} (structure type W₅Si₃, tI32, I4/mcm, a = 11.1005(9)-11.1829(12), c = 5.4537(5)-5.5449(6) Å). Their structures are characterized by partial ordering of Al and Sn atoms. The structure of ZrAl_2.68Sn_0.32 presents a cubic close-packed arrangement of atoms and is thus built up from cuboctahedra. The structures of the Zr-rich phases are built up from columns of octahedra (Zr₅Al_0-1Sn_4-3), and square antiprisms and tetrahedra (Zr₅Al_2.71Sn_0.29 and Zr₅Al_1.68-0.40Sn_1.32-2.60).

Isothermal section of the phase diagram of the ternary system Zr–Al–Sn at 600°C.

Keywords

Zirconium / Aluminum / Tin / X-ray powder diffraction / Energy-dispersive X-ray spectroscopy / Phase diagram / Solid solution / Ternary compound / Crystal structure