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Homo- and Heterovalent Substitutions in the New Clathrates I Si(30)P(16)Te(8-x)Se(x) and Si(30+x)P(16-x)Te(8-x)Br(x): Synthesis, Crystal Structure, and Thermoelectric Properties.
MedLine Citation:
PMID:  23072375     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
The new cationic clathrates I Si(30)P(16)Te(8-x)Se(x) and Si(30+x)P(16-x)Te(8-x)Br(x) were synthesized by the standard ampule technique. The Si(30)P(16)Te(8-x)Se(x) (x = 0-2.3) clathrates crystallize in the cubic space group Pm3̅n with the unit cell parameter a ranging from 9.9382(2) to 9.9696(1) Å. In the case of the Si(30+x)P(16-x)Te(8-x)Br(x) (x = 1-6.4) clathrates, the lattice parameter varies from 9.9720(8) to 10.0405(1) Å; at lower Si/P ratios (x = 1-3) 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 × 10(-6) to 1.0 × 10(-5) K(-1) in the temperature range of 298-1100 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.
Authors:
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
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-16
Journal Detail:
Title:  Inorganic chemistry     Volume:  -     ISSN:  1520-510X     ISO Abbreviation:  Inorg Chem     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-17     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0366543     Medline TA:  Inorg Chem     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
Max-Planck-Institute für Chemische Physik fester Stoffe , Noethnitzer Str. 40, 01187 Dresden, Germany.
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