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Synthesis and first‐principles calculations of the structural and electronic properties of type‐I clathrates Sr 8 Ga 16 Sn x Ge 30 − x
Author(s) -
Li D. C.,
Fang L.,
Deng S. K.,
Kang K. Y.,
Wei W. H.,
Ruan H. B.
Publication year - 2012
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201147488
Subject(s) - band gap , anharmonicity , materials science , lattice constant , thermoelectric effect , density functional theory , electronic structure , crystal structure , semiconductor , bulk modulus , structural stability , direct and indirect band gaps , electronic band structure , condensed matter physics , thermoelectric materials , diffraction , thermal stability , crystallography , computational chemistry , thermodynamics , chemistry , physics , composite material , optoelectronics , structural engineering , engineering , organic chemistry , optics
In the present work we report on the synthesis of type‐I clathrates Sr 8 Ga 16 Sn x Ge 30 − x (0 ≤ x ≤ 12). To find out how the substitution of Sn for Ge affects structural stability and electronic structure, the structural and electronic properties for Sr 8 Ga 16 Sn x Ge 30 − x (0 ≤ x ≤ 30) have been investigated by a first‐principles method based on the density‐functional theory (DFT). We found that the lattice constants of Sr 8 Ga 16 Sn x Ge 30 − x series increase with increasing Sn content, which is consistent with X‐ray diffraction (XRD) results. Calculations indicate that the substitution of Sn for Ge leads to the change of the bulk modulus and the decrease of stability of the structure. It is found that these alloys are all indirect‐gap semiconductors and the bandgap decreases from about 0.36 eV in Sr 8 Ga 16 Ge 30 to about 0.03 eV in Sr 8 Ga 16 Sn 30 with increasing Sn content. The decrease of the bandgap is attributed to the increase of the free space for the Sr guest motion, which is accompanied by the guest's low‐energy modes and larger anharmonicity. These mean that an increase in the ratio of Sn‐to‐Ge can not only control the electrical properties of the materials, but also may reduce their thermal conductivity, suggesting that cage‐size tuning is one of the useful means to obtain high‐performance thermoelectric (TE) materials.