Solution-based synthesis of thermoelectric nanoplates, which provides a low thermal conductivity due to the grain boundary scattering, has received considerable attention as a scalable method. However, the scattering also decreased electrical conductivity leading to a low thermoelectric figure of merit (ZT). Here we employed expanded graphene to enhance thermoelectric performance of p-type Bi0.5Sb1.5Te3 composites by simultaneous improvement in electrical conduction and phonon scattering. The addition of expanded graphene (0.1vol%) improved both carrier concentration and electrical conductivity of composites due to the high intrinsic p-type carrier concentration of graphene. Besides, it significantly decreased lattice thermal conductivity due to the phase boundary phonon scattering in spite of the high intrinsic thermal conductivity of graphene. The increased carrier concentration also suppressed the bipolar conduction resulting in a moderate increase in power factor and a slow increase in bipolar thermal conductivity at elevated temperatures. Overall, the maximum ZT increased by 45% (1.13 at 360K) by the addition of expanded graphene. A similar trend with a greater maximum ZT (1.24 at 360K) was observed when ball-milled Bi0.5Sb1.5Te3 ingot powders were employed providing reliability of the suggested mechanism.
Bibliographical noteFunding Information:
This work was supported by IBS-R011-D1, the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (NRF- 2014R1A2A1A10050639 ), and the Human Resources Development program (no. 20124010203270 ) of the KETEP grant funded by the Korean government Ministry of Knowledge Economy .
© 2015 Elsevier Ltd.
All Science Journal Classification (ASJC) codes
- Renewable Energy, Sustainability and the Environment
- Materials Science(all)
- Electrical and Electronic Engineering