Experimental characterization confirms distinct Tl2Te and Tl5Te3 crystal phases in the Tl–Pb–Te system, indicating clear boundaries for growing functional thermoelectric materials.
Key Points
To resolve conflicting reports regarding the structural distinctiveness of binary Tl2Te and Tl5Te3 phases and construct the phase equilibria of the Tl–Pb–Te ternary system.
Grew high-quality single crystals using directed crystallization.
Characterized phases and crystal structures using differential thermal analysis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and microstructural analyses on samples annealed at 473 K.
Confirmed Tl2Te forms a distinct monoclinic lattice (space group C2/c, a = 15.610 Å, b = 8.914 Å, c = 31.069 Å, β = 100.5°), whereas Tl5Te3 crystallizes in a tetragonal lattice (space group I4/mcm, a = 8.931 Å, c = 12.595 Å).
Constructed a triangulation scheme for the Tl–Pb–Te system identifying eight quasi-binary cross-sections.
Demonstrated that ternary Tl4PbTe3 forms extensive solid-solution regions spanning over 85 mol% with Tl5Te3 and over 80 mol% with Tl2Te.