Tunable Electrical Conductivity and Simultaneously Enhanced Thermoelectric and Mechanical Properties in n‐type Bi<sub>2</sub>Te<sub>3</sub>
L. K. V. LOU, Jianming Yang, Yuke Zhu, Hao Liang, Yixin Zhang, Jing Feng, Jiaqing He, Zhen‐Hua Ge, Li‐Dong Zhao
Abstract
Abstract The recent growing energy crisis draws considerable attention to high‐performance thermoelectric materials. n‐type bismuth telluride is still irreplaceable at near room temperature for commercial application, and therefore, is worthy of further investigation. In this work, nanostructured Bi 2 Te 3 polycrystalline materials with highly enhanced thermoelectric properties are obtained by alkali metal Na solid solution. Na is chosen as the cation site dopant for n‐type polycrystalline Bi 2 Te 3 . Na enters the Bi site, introducing holes in the Bi 2 Te 3 matrix and rendering the electrical conductivity tunable from 300 to 1800 Scm –1 . The solid solution limit of Na in Bi 2 Te 3 exceeds 0.3 wt%. Owing to the effective solid solution, the Fermi level of Bi 2 Te 3 is properly regulated, leading to an improved Seebeck coefficient. In addition, the scattering of both charge carriers and phonons is modulated, which ensured a high‐power factor and low lattice thermal conductivity. Benefitting from the synergistic optimization of both electrical and thermal transport properties, a maximum figure of merit ( ZT) of 1.03 is achieved at 303 K when the doping content is 0.25 wt%, which is 70% higher than that of the pristine sample. This work disclosed an effective strategy for enhancing the performance of n‐type bismuth telluride‐based alloy materials.