Phase
equilibria in the Tl2S–PbS–GeS2 system and crystal structure of Tl0.5Pb1.75GeS4
Chem.
Met. Alloys 5 (2012) 37-41
https://doi.org/10.30970/cma5.0205
M.Yu. MOZOLYUK, L.V. PISKACH, A.O. FEDORCHUK, I.D. OLEKSEYUK,
O.V. PARASYUK
The phase equilibria in the quasi-ternary
system Tl2S–PbS–GeS2 at 520 K were investigated by
XRD methods. Three intermediate quaternary phases were discovered, Tl2PbGeS4,
~Tl2PbGe3S8
and Tl0.5Pb1.75GeS4. The crystal structure of
the quaternary phase Tl0.5Pb1.75GeS4 was determined
by powder XRD in the non-centrosymmetric space group I-43d, Z = 16
and a = 1.420082(6) nm (Ag0.5Pb1.75GeS4
structure type). Atomic parameters were refined in the isotropic approximation
(RI = 0.0496, Rp = 0.0944). The phase
diagram of the Tl2GeS3–PbS section was investigated. The
section is quasi-binary, of the eutectic type, with formation of the equimolar
compound Tl2PbGeS4, which melts incongruently at
781 K and undergoes a polymorphous transformation at 688 K. The ÍÒ-modification crystallizes with a
monoclinic structure (S.G. P12/a1, à =
0.89079(7), b = 0.90951(7), c = 1.04772(7) nm, β = 94.116(7)°).
Fragment of the Tl0.5Pb1.75GeS4 structure where Ge-centered tetrahedron is surrounded
by the atoms of metallic components, and mutual positions of the thermal ellipsoids of atoms
Keywords
Thallium
chalcogenides / Crystal structure / Phase diagram / Isothermal section