Studies on Thermoelectric Properties of n-type Polycrystalline SnSe sub(1-x)S sub(x) by Iodine Doping

Iodine-doped n-type SnSe polycrystalline by melting and hot pressing is prepared. The prepared material is anisotropic with a peak ZT of approximately 0.8 at about 773 K measured along the hot pressing direction. This is the first report on thermoelectric properties of n-type Sn chalcogenide alloys. With increasing content of iodine, the carrier concentration changed from 2.3 10 super(17) cm super(-3) (p-type) to 5.0 10 super(15) cm super(-3) (n-type) then to 2.0 10 super(17) cm super(-3) (n-type). The decent ZT is mainly attributed to the intrinsically low thermal conductivity due to the high anharmonicity of the chemical bonds like those in p-type SnSe. By alloying with 10 at% SnS, even lower thermal conductivity and an enhanced Seebeck coefficient were achieved, leading to an increased ZT of approximately 1.0 at about 773 K measured also along the hot pressing direction. For the first time, TE properties of n-type Sn chalcogenide polycrystal materials are reported. By doping with iodine, the n sub(H) changes from 2.3 10 super(17) cm super(-3) (p-type) to 5.0 10 super(15) cm super(-3) (n-type) then to 2.0 10 super(17) cm super(-3) (n-type). By alloying with SnS, the lowered thermal conductivity and enhanced Seebeck coefficient contribute to a highest ZT of approximately 1.0 at 773 K for SnSe sub(0.87)S sub(0.1)I sub(0.03) polycrystals.