Microstructure Optimization in the Shear‐Exfoliated Bi6Cu2Se4O6 through Introducing Reduced Graphene Oxide Leads to Wide‐Ranged Thermoelectric Performance

Author:

Zheng Junqing1,Wen Yi1ORCID,Wang Sining1,Li Yichen1,Wang Siqi1,Zhao Zhe1,Liu Shan1,Liu Shibo1,Gao Xiang2,Zhao Li‐Dong13ORCID

Affiliation:

1. School of Materials Science and Engineering Beihang University Beijing 100191 China

2. Center for High Pressure Science and Technology Advanced Research (HPSTAR) Beijing 100094 China

3. Tianmushan Laboratory Yuhang District Hangzhou 311115 China

Abstract

AbstractBi6Cu2Se4O6 is considered as an ideal n‐type thermoelectric material to pair with p‐type BiCuSeO for preparing oxyselenide‐based thermoelectric devices, but its thermoelectric performance is limited by poor electrical conductivity. In this research, the reduced graphene oxide (rGO) nanosheets are introduced into Bi6Cu2Se3.6Cl0.4O6 matrix through liquid‐phase shear exfoliation to modify the microstructure. rGO can insert into matrix grains as intercalations, or embed into grain boundaries as wetting phase, and prompt grain alignment, which contributes to the significantly enhanced carrier mobility, thus leading to an improvement in electrical conductivity from ≈15 S cm−1 to ≈230 S cm−1 at 303 K. Whereafter, the effective donor dopant Nb is chosen to substitute Bi. The carrier concentration is increased without damaging the carrier mobility, resulting in a further improved electrical conductivity of ≈840 S cm−1 at 303 K. Lattice thermal conductivity is also suppressed owing to the intensive phonon scattering by point defects and grain boundaries. Ultimately, a record‐breaking peak ZT ≈0.5 (873 K) and average ZT ≈0.3 (303–873 K) can be achieved in Bi5.91Nb0.09Cu2Se3.6Cl0.4O6 + 0.5% rGO. The microstructure optimization method in this research effectively improves thermoelectric performance, and is anticipated to be applied in other thermoelectrics.

Funder

National Key Research and Development Program of China

National Natural Science Foundation of China

Natural Science Foundation of Beijing Municipality

Higher Education Discipline Innovation Project

National Science Fund for Distinguished Young Scholars

China Postdoctoral Science Foundation

Publisher

Wiley

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