title: A thermoelectric zintl phase Na2+x Ga2+x Sn4-x with disordered Na atoms in helical tunnels.
abstract: A polycrystalline sample of Na2+x Ga2+x Sn4-x with x = 0.19 has low thermal conductivities of 0.56 and 0.58 W m(-1) K(-1) due to static and dynamic positional disorder of Na atoms in the crystal structure and dimensionless figures of merit (ZT values) values of 0.98 and 1.28 at 295 and 340 K, respectively. The performance is comparable to those of commercial Bi2 Te3 -based materials.
authors.affiliation: Institute of Multidisciplinary Research for Advanced Material, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Institute of Multidisciplinary Research for Advanced Material, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
authors.forename: Hisanori
authors.initials: H
authors.lastname: Yamane
authors.affiliation: National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, 305-8565, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Nagai
keywords: Zintl phase; crystal structures; rattling; thermoelectric materials