Crystal structure, electronic structure and physical properties of the new low-valent thallium silicon telluride Tl6Si2Te6 in comparison to Tl6Ge2Te6 |
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Authors: | Abdeljalil Assoud |
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Affiliation: | Department of Chemistry, University of Waterloo, Waterloo, Ont., Canada N2L 3G1 |
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Abstract: | The title compounds were prepared from the elements in the stoichiometric ratio at 800 °C under exclusion of air. Tl6Si2Te6 crystallizes in the space group P1¯, isostructural with Tl6Ge2Te6, with , , , α=89.158(2)°, β=96.544(2)°, γ=100.685(2)°, (Z=2). Its structure is composed of dimeric [Si2Te6]6− units with a Si-Si single bond, while the Tl atoms are irregularly coordinated by five to six Te atoms. Numerous weakly bonding Tl-Tl contacts exist. Both title compounds are black semiconductors with small band gaps, calculated to be 0.9 eV for Tl6Si2Te6 and 0.5 eV for Tl6Ge2Te6. The Seebeck coefficients are +65 μV K−1 in case of Tl6Si2Te6 and +150 μV K−1 in case of Tl6Ge2Te6 at 300 K, and the electrical conductivities are 5.5 and 3 Ω−1 cm−1, respectively. |
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Keywords: | Thallium Silicon Telluride Crystal structure Electronic structure Semiconductor |
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