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 Zr5AlxSn4-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: ZrAl2.682(4)Sn0.318(4) (structure
type TiAl3, tI8, I4/mmm, a = 3.98855(18),
ñ = 9.0848(4) Å), Zr5Al2.71(1)Sn0.29(1)
(structure type W5Si3, tI32, I4/mcm, a = 11.0530(9),
c = 5.4071(5) Å), and Zr5Al1.68(3)-0.40(1)Sn1.32(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 ZrAl2.68Sn0.32
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 (Zr5Al0-1Sn4-3),
and square antiprisms and tetrahedra (Zr5Al2.71Sn0.29
and Zr5Al1.68-0.40Sn1.32-2.60).
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