Texturing degree boosts thermoelectric performance of silver-doped polycrystalline SnSe

Xue Wang,Debo Li,Hezhu Shao,Tianya Tan,Jun Jiang,Guo-Qiang Liu,Xiaojian Tan,Jingtao Xu

doi:10.1038/am.2017.147

Abstract

Tin selenite (SnSe) has attracted significant attention due to its record thermoelectric figure of merit (ZT=2.6 at 923 K) of its single crystal. However, the polycrystalline SnSe processes considerably less ZTs (⩽1.1). In this study, we investigate the thermoelectric properties of Ag-doped polycrystalline SnSe, which was synthesized via zone melting and hot pressing. By comparing our results and previous reports of Ag-doped single crystals and polycrystals, we determine that the high texturing degree is essential for achieving good thermoelectric performance in polycrystalline SnSe. The zone-melted Sn0.99Ag0.02Se shows better thermoelectric performance than the Ag-doped SnSe single crystal in the entire temperature range, exhibiting a peak ZT of 1.3 at 793 K.

Highlights

Thermoelectric materials, which are able to directly convert heat energy into electrical power, have received global attention.[1,2,3,4] The efficiency of thermoelectric devices is determined via the dimensionless figure of merit, which is defined as ZT = S2σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity and T is the absolute temperature
The thermoelectric performance has been significantly improved in the past two decades through new understanding of transport properties,[5,6,7,8] and ZT records have been continuously renewed in thermoelectric materials.[6,7,8,9,10]
It has been reported that Ag doping increases the carrier concentration of SnSe, which leads to the enhanced thermoelectric properties

Summary

Introduction

Thermoelectric materials, which are able to directly convert heat energy into electrical power, have received global attention.[1,2,3,4] The efficiency of thermoelectric devices is determined via the dimensionless figure of merit, which is defined as ZT = S2σT/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity and T is the absolute temperature. The IV–VI compound SnSe has received considerable attention because of its ultrahigh thermoelectric performance in both undoped and p-type-doped single crystals (SCs).[11,12,13] SnSe has a layered structure (with a Pnma space group, #62 at room temperature) and strong anisotropic properties. The a axis possesses an ultralow thermal conductivity but low ZTs. High thermoelectric performance is observed in the bc plane, ZT = 2.62 at 923 K along the b axis and 2.3 along the c axis. Because of poor machinability and difficulties of growing SCs, increasing attention has been paid to its polycrystalline counterparts

Methods

Results

Conclusion