High thermoelectric performance and low thermal conductivity in K-doped SnSe polycrystalline compounds

• Published in: Current applied physics Vol. 18; no. 12; pp. 1534 - 1539
• Main Authors: Lin, Chan-Chieh, Ginting, Dianta, Kim, Gareoung, Ahn, Kyunghan, Rhyee, Jong-Soo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2018; 한국물리학회
• Subjects: Low thermal conductivity; Mobility; SnSe; Thermoelectric; 물리학; Mobility; Low thermal conductivity; Thermoelectric; ZT; SnSe
• ISSN: 1567-1739; 1878-1675
• DOI: 10.1016/j.cap.2018.09.011

SnSe single crystal showed a high thermoelectric zT of 2.6 at 923 K mainly due to an extremely low thermal conductivity 0.23 W m−1 K−1. It has anisotropic crystal structure resulting in deterioration of thermoelectric performance in polycrystalline SnSe, providing a low zT of 0.6 and 0.8 for Ag and Na-doped SnSe, respectively. Here, we presented the thermoelectric properties on the K-doped KxSn1−xSe (x = 0, 0.1, 0.3, 0.5, 1.5, and 2.0%) polycrystals, synthesized by a high-temperature melting and hot-press sintering with annealing process. The K-doping in SnSe efficiently enhances the hole carrier concentration without significant degradation of carrier mobility. We find that there exist widespread Se-rich precipitates, inducing strong phonon scattering and thus resulting in a very low thermal conductivity. Due to low thermal conductivity and moderate power factor, the K0.001Sn0.999Se sample shows an exceptionally high zT of 1.11 at 823 K which is significantly enhanced value in polycrystalline compounds. Temperature-dependent thermal conductivity κ (a) and dimensionless figure-of-merit zT values for KxSn1-xSe (x = 0.0, 0.1, 0.3, 0.5, 1.5, and 2.0 mol.%) compounds. [Display omitted] •The zT value of polycrystalline SnSe remains relatively low value.•K-doping in SnSe efficiently enhances the hole carrier concentration.•There exist prevalent Se-rich precipitates in the SnSe matrix, resulting in a very low thermal conductivity.•The K0.001Sn0.999Se sample shows an exceptionally high zT of 1.11 at 823 K.