Synthesis and thermoelectric properties of quaternary Si clathrate K 8−δ Ga x Zn y Si 46− x − y
Year: 2017
Type: article
Abstract: The thermoelectric properties of quaternary Si clathrates, K 8−δ Ga x Zn y Si 46− x − y , were investigated at temperatures from 10 to 320 K to determine the effects of Ga atom substitution by an aliovalent atom, Zn, on the thermoelectric properties of the ternary Si clathrate K 8 Ga 8 Si 38 . Only a small amount of Ga atoms could be substituted by Zn, 0 ≤ y ≤ 0.8, and the lattice constant of K 8−δ Ga x Zn y Si 46− x decreased with an increase in the Zn content, y . Zn substitution significantly changed the transport properties of the clathrate. Measurements of electrical resistivity and the Seebeck coefficient, S , revealed that the conduction mechanism changed from variable range hopping to metallic conduction with an increase of y . S for all of the samples was negative, which indicates that the dominant carriers were electrons, and the absolute value of S decreased as y increased. All the specimens had approximately the same thermal conductivity of ca. 1.6 W K −1 m −1 at 300 K. K 7.6 Ga 5.8 Zn 0.8 Si 39.6 exhibited the largest power factor, and therefore the highest thermoelectric dimensionless figure of merit ZT , of 0.0096 at 320 K, which is approximately twice that for the ternary Si clathrate K 7.4 Ga 7.7 Si 38.9 . Thus, Zn substitution enhances the ZT of K 7.4 Ga 7.7 Si 38.9 .
Institution: National Institute for Materials Science
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W2588587901