Abstract
The first arsenide clathrates A 8Zn 18As 28 (A = K, Rb, Cs) and Cs 8Cd 18As 28 have been synthesized in high yields via a two-step route. These compounds adopt the type-I structure and exhibit structural characteristics different from the recently reported antimonide clathrates Cs 8Zn 18Sb 28 and Cs 8Cd 18Sb 28. In arsenide clathrates, Zn (or Cd) and As atoms are statistically mixed at the three framework sites: 6c, 16i, and 24k; the alkali metals reside inside the cages at the 2a and 6d sites, with the 2a site being only partially filled. Single-crystal X-ray diffraction studies confirm that the Cd atoms preferably occupy the 6c and 24k sites over the 16i site, with more than 80% of Cd found at the former two positions. A unique structural feature is a framework disorder coupled with the partial occupancy of the cage's 2a site. Optical absorption measurements and electronic property measurements reveal a semimetallic-like behavior for Cs 8Cd 18As 28 and semiconductor-like behavior for A 8Zn 18As 28 (A = Rb, Cs).
Original language | English (US) |
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Pages (from-to) | 3596-3603 |
Number of pages | 8 |
Journal | Chemistry of Materials |
Volume | 24 |
Issue number | 18 |
DOIs | |
State | Published - Sep 25 2012 |
Keywords
- arsenides
- clathrates
- crystal structure
- thermoelectrics
ASJC Scopus subject areas
- Chemistry(all)
- Chemical Engineering(all)
- Materials Chemistry