Premium
A Combined Metal–Halide/Metal Flux Synthetic Route towards Type‐I Clathrates: Crystal Structures and Thermoelectric Properties of A 8 Al 8 Si 38 (A=K, Rb, and Cs)
Author(s) -
Baran Volodymyr,
Senyshyn Anatoliy,
Karttunen Antti J.,
Fischer Andreas,
Scherer Wolfgang,
RaudaschlSieber Gabriele,
Fässler Thomas F.
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201403416
Subject(s) - seebeck coefficient , electrical resistivity and conductivity , halide , thermoelectric effect , analytical chemistry (journal) , alkali metal , materials science , neutron diffraction , single crystal , crystallinity , chemistry , crystal structure , thermal conductivity , inorganic chemistry , crystallography , thermodynamics , physics , electrical engineering , organic chemistry , chromatography , engineering , composite material
Single‐phase samples of the compounds K 8 Al 8 Si 38 ( 1 ), Rb 8 Al 8 Si 38 ( 2 ), and Cs 7.9 Al 7.9 Si 38.1 ( 3 ) were obtained with high crystallinity and in good quantities by using a novel flux method with two different flux materials, such as Al and the respective alkali‐metal halide salt (KBr, RbCl, and CsCl). This approach facilitates the removal of the product mixture from the container and also allows convenient extraction of the flux media due to the good solubility of the halide salts in water. The products were analyzed by means of single‐crystal X‐ray structure determination, powder X‐ray and neutron diffraction experiments, 27 Al‐MAS NMR spectroscopy measurements, quantum chemical calculations, as well as magnetic and transport measurements (thermal conductivity, electrical resistivity, and Seebeck coefficient). Due to the excellent quality of the neutron diffraction data, the difference between the nuclear scattering factors of silicon and aluminum atoms was sufficient to refine their mixed occupancy at specific sites. The role of variable‐range hopping for the interpretation of the resistivity and the Seebeck coefficient is discussed.