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Synthesis, Crystal Structure, and Thermoelectric Properties of Clathrates in the Sn‐In‐As‐I System
Author(s) -
Kelm Evgeny A.,
Olenev Andrei V.,
Bykov Mikhail A.,
Sobolev Alexey V.,
Presniakov Igor A.,
Kulbachinskii Vladimir A.,
Kytin Vladimir G.,
Shevelkov Andrei V.
Publication year - 2011
Publication title -
zeitschrift für anorganische und allgemeine chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.354
H-Index - 66
eISSN - 1521-3749
pISSN - 0044-2313
DOI - 10.1002/zaac.201100287
Subject(s) - seebeck coefficient , indium , thermoelectric effect , crystal structure , crystallography , materials science , single crystal , crystal (programming language) , figure of merit , tin , chemistry , analytical chemistry (journal) , thermodynamics , physics , optoelectronics , metallurgy , organic chemistry , computer science , programming language
Clathrates of the general formula Sn 24– x – δ In x As 22– y I 8 have been synthesized with x max = 10.7. They crystallize in the clathrate‐I type of crystal structure, space group Pm $\bar{3}$ n , with the cubic unit cell parameter ranging from a = 11.088 ( x = 0) to a = 11.343 ( x = 10.7) Å. The crystal structure refined for five compositions with different indium contents revealed that despite the linear dependence of the unit cell parameter upon x the details of the crystal structure change twice upon varying the indium contents. These changes occur without altering the space group and show up in positional disorder of atoms within the framework and the concomitant change of the coordination of part of tin atoms from 3+2 to 3+3, which is additionally confirmed by the Mössbauer spectroscopy data. In general, these changes reflect the transition from the Sn 24 P 19.3 I 8 structure type for high indium contents to the Sn 20.5 As 22 I 8 structure type for low indium contents. It is shown that the Sn 24– x – δ In x As 22– y I 8 clathrates have n ‐type conductivity with high values of the Seebeck coefficient ranging from –322 to –594 μV·K –1 at room temperature. They display an abnormally low thermal conductivity at 293 K, from 0.36 to 0.57 W·m –1 ·K –1 . The calculated thermoelectric figure‐of‐merit for Sn 24– x– δ In x As 22– y I 8 has its room‐temperature maximum at 0.041 for x = 6.5.