Dr. Kai Guo
School of Materials Science and Engineering, Shanghai University, China

Speech Title: Realizing High Thermoelectric Performance in BaCu_2-xAg_xTe₂ Through Enhanced Carrier Effective Mass and Point-Defect Scattering

Abstract: With the aim of realizing mid-temperature thermoelectric materials, the electrical and thermal transport properties of the Zintl phase compound BaCu₂Te₂ with a channel structure (Pnma) were systematically investigated. BaCu₂Te₂ exhibits moderate electrical transport properties and low intrinsic thermal conductivity, which contribute to its high thermoelectric figure of merit (zT = 0.72 at 823 K). The partial substitution of Cu with Ag led to a significant enhancement of the Seebeck coefficient, as the carrier effective mass increased from 1.0m₀ for BaCu₂Te₂ to 1.5m₀ for BaCu_1.9Ag_0.1Te₂ at room temperature, and reduction of the Hall carrier concentration. In addition, at higher temperature, a lower thermal conductivity of ~0.5 W m⁻¹K⁻¹ was achieved for BaCu_1.9Ag_0.1Te₂; this reduced thermal conductivity resulted from the point-defect scattering arising from the Ag/Cu isovalent substitution. Together, these integrated effects led to a significant improvement of the quality factor β with a peak thermoelectric figure of merit zT of 1.08 for BaCu_1.9Ag_0.1Te₂ at 823 K. The average zT of BaCu_1.9Ag_0.1Te₂ over the temperature range of 323–823 K was 0.68, demonstrating its potential as a promising thermoelectric Zintl compound in the mid-temperature range.

Acknowledgements: This work was financially supported by the National Natural Science Foundation of China under Projects 21501118, 21771123, and 51632005, Shanghai Municipal Science and Technology Commission under Project 15DZ2260300, Key Laboratory of Optoelectronic Materials Chemistry and Physics, Chinese Academy of Sciences (Grant 2008DP173016), and the Programme of Introducing Talents of Discipline to Universities (Grant D16002). K.G. gratefully acknowledges the support of Young Eastern Scholar Project of Shanghai Municipal Education Commission (Grant QD2015031).