Crystal structure, electronic structure and physical properties of a new semiconducting thallium antimony selenide: Tl2.35Sb8.65Se14

A new ternary thallium selenide has been synthesized from the elements in the stoichiometric ratio at 650 °C under vacuum. Tl2.35Sb8.65Se14 crystallizes in the space group P21/m with a = 17.201(2) Å, b = 4.0792(5) Å, c = 21.196(3) Å, β = 109.303(3)°, V = 1403.6(3) Å3. The structure is composed of distorted edge-sharing SbSe6 octahedra, while the Tl atoms are coordinated by 8–9 Se atoms. The title compound is a black semiconductor in accord with the electronic structure calculation. Transport property measurements confirm that this compound is an n-type semiconductor with an electrical conductivity of σ = 3.9 × 10−4 Ω−1 cm−1 and a Seebeck coefficient of S = −452 μV K−1 at 300 K. The optical band gap was determined via spectroscopy to be 0.6 eV.

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