Homo- and Heterovalent Substitutions in the New Clathrates I Si30P16Te8鈥?i>xSex and Si30+xP16鈥?i>xTe8鈥?i>x<

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• 作者：Nikolay S. Abramchuk ; Wilder Carrillo-Cabrera ; Igor Veremchuk ; Niels Oeschler ; Andrei V. Olenev ; Yurii Prots ; Ulrich Burkhardt ; Evgeny V. Dikarev ; Juri Grin ; Andrei V. Shevelkov
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：November 5, 2012
• 年：2012
• 卷：51
• 期：21
• 页码：11396-11405
• 全文大小：582K
• 年卷期：v.51,no.21(November 5, 2012)
• ISSN：1520-510X

文摘

The new cationic clathrates I Si₃₀P₁₆Te_8鈥?i>xSe_x and Si_30+xP_16鈥?i>xTe_8鈥?i>xBr_x were synthesized by the standard ampule technique. The Si₃₀P₁₆Te_8鈥?i>xSe_x (x = 0鈥?.3) clathrates crystallize in the cubic space group Pm3̅n with the unit cell parameter a ranging from 9.9382(2) to 9.9696(1) 脜. In the case of the Si_30+xP_16鈥?i>xTe_8鈥?i>xBr_x (x = 1鈥?.4) clathrates, the lattice parameter varies from 9.9720(8) to 10.0405(1) 脜; at lower Si/P ratios (x = 1鈥?) the ordering of bromine atoms induces the splitting of the guest positions and causes the transformation from the space group Pm3̅n to Pm3̅. Irrespective of the structure peculiarities, the normal temperature motion of the guest atoms inside the oversized cages of the framework is observed. The title clathrates possess very low thermal expansion coefficients ranging from 6.6 脳 10^鈥? to 1.0 脳 10^鈥? K^鈥? in the temperature range of 298鈥?100 K. The characteristic Debye temperature is about 490 K. Measurements of the electrical resistivity and thermopower showed typical behavior of p-type thermally activated semiconductors, whereas the temperature behavior of the thermal conductivity is glasslike and in general consistent with the PGEC concept. The highest value of the thermoelectric figure of merit (ZT = 0.1) was achieved for the Br-bearing clathrate Si_32.1(2)P_13.9(2)Te_6.6(2)Br_1.0(1) at 750 K.