title: Preparation and thermoelectric properties of sintered type-I clathrates K8Ga(x)Sn(46-x).
abstract: Polycrystalline clathrate samples of nominal K(8)Ga(x)Sn(46-x) were prepared by the spark plasma sintering method to investigate their crystal structures, mobilities and thermoelectric properties. The samples almost had a single-phase type-I clathrate structure, and their relative densities reached as high as 98%. The room-temperature mobility of the K(8)Ga(8)Sn(38) sample was 25 cm(2) V(-1) s(-1), which substantially exceeded the reported mobilities of Rb- and Cs-containing Sn clathrates. Moreover, the mobility was larger than those of the type-I Ba(8)Ga(16)Sn(30), which had more Ga substituting atoms in unit cell. A higher mobility might accordingly be achieved in thermoelectric clathrates with a smaller number of substituting atoms. Their electrical conductivities and Seebeck coefficients in the temperature range 300-450 K were typical of n-type doped semiconductors in the extrinsic region while their room-temperature lattice thermal conductivities were as low as approximately 11 mW cm(-1) K(-1). The maximum dimensionless figure of merit ZT was estimated to be 0.27 at 490 K from the Seebeck coefficient of -262 microV K(-1) and the electrical conductivity of 96 S cm(-1) for the K(8)Ga(8)Sn(38) sample with a carrier concentration of 2.9 x 10(19) cm(-3).
authors.affiliation: Department of Electrical and Electronic Engineering, Yamaguchi University, 2-16-1, Tokiwadai, Ube 755-8611, Japan.
authors.forename: Masahiro
authors.initials: M
authors.lastname: Hayashi
authors.forename: Kengo
authors.initials: K
authors.lastname: Kishimoto
authors.forename: Kazuma
authors.initials: K
authors.lastname: Kishio
authors.forename: Koji
authors.initials: K
authors.lastname: Akai
authors.forename: Hironori
authors.initials: H
authors.lastname: Asada
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Koyanagi