Dislocation arrays embedded in low-angle grain-boundaries have emerged as an effective structural defect for a dramatic improvement of thermoelectric performance by reducing thermal conductivity . A transient liquid-flow assisted compacting process has been employed for p-type Bi0.5Sb1.5Te3 material to generate the dislocation arrays at grain-boundaries. The details of underlying formation mechanism are crucial for the feasibility of the process on other state-of-the-art thermoelectric materials but have not been well understood. Here, we report the direct observation of dislocation formation process at grain-boundaries of Sb2Te3 system as a proof-of-concept material. We found that the formation of homointerface between Te-terminated Sb2Te3 matrix phase and Te liquid atomic-layer of secondary phase is a prerequisite factor to achieve the low-energy liquid-solid homointerface at compacting elevated temperature. We further demonstrate from the successful observations of atomic structure in the intermediate state of the compacted pellet that the high self-diffusion rate of Te atoms at the liquid-solid homointerface facilitates an effective grain rearrangement, generating low-energy grain-boundaries embedded with dense dislocation arrays. These results pave the way to improve thermoelectric performance of various materials where dislocation arrays are generated by transient liquid-flow assisted compacting process using precursors with an interface constructed with the same types of atoms.
Bibliographical noteFunding Information:
This work was supported by IBS-R011-D1, by the National Research Foundation (NRF) Grant funded by the Korean Government (MSIP) ( NRF-2015R1A5A1036133 and NRF-2017R1A2B3011949 ) and by the Creative Materials Discovery Program through the NRF funded by the Ministry of Science and ICT ( NRF-2015M3D1A1070639 ).
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Ceramics and Composites
- Polymers and Plastics
- Metals and Alloys