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 1.0m 0 for BaCu2Te2 to 1.5m 0 for BaCu1.9Ag0.1Te2 at room temperature, and reduction of the Hall carrier concentration. In addition, at higher temperature, a lower thermal conductivity of ∼0.5 W m–1 K–1 was achieved for BaCu1.9Ag0.1Te2; 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 BaCu1.9Ag0.1Te2 at 823 K. The average zT of BaCu1.9Ag0.1Te2 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.

Thermoelectric Properties of (Ba,K)Zn2As2 Crystallized in the ThCr2Si2-type Structure

“…For instance, the ZT value of (Ba,K)­Cd 2 As 2 is 0.81 at 762 K . AT 2 X 2 compounds crystallized in the α-BaCu 2 S 2 structure (space group Pnma ) also exhibit high thermoelectric performance. − For example, (Ba,K)­Zn 2 As 2 and (Ba,Na)­Cu 2 Se 2 exhibit a ZT value of 0.67 at 900 K and 1 at 773 K, respectively. , …”

Zintl Phase Yb1–xBaxMg2Bi1.98 Compounds with Enhanced Thermoelectric Performance Caused by Cation Substitution

“…Thermoelectric technology, as a clean and sustainable energy conversion method, has been intensively investigated owing to its possible applications in waste-heat power generation and Fluoride-free refrigeration. − The energy conversation efficiency is directly limited by the materials’ performance, which is quantified by the dimensionless figure of merit (ZT), ZT = ( S 2 σ/κ) T , where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity that contains electronic thermal conductivity κ e and lattice thermal conductivity κ L , and T is the absolute temperature. , A promising thermoelectric material is supposed to simultaneously possess low thermal conductivity and remarkable electrical transport performance, which can be determined by the power factor PF = S 2 σ. Several effective approaches, e.g., carrier concentration optimization, − band engineering, − and microstructural defects, − have been brought forward to optimize thermoelectric performance. However, the strongly intertwined connections among S , σ, and κ e gravely hinder the thoroughly improvement of ZT values …”

Effective Mass Enhancement and Thermal Conductivity Reduction for Improving the Thermoelectric Properties of Pseudo‐Binary Ge2Sb2Te5

“…In this situation, improving the thermoelectric properties becomes an enormous challenge for thermoelectric researchers. Some successful strategies such as band convergence, [ 4–6 ] nanostructure engineering, [ 7,8 ] multiscale phonon scattering including point defect scattering and grain boundary scattering, [ 9,10 ] have been proposed in these years.…”