Thermoelectric Zintl Compound In1−xGaxTe: Pure Acoustic Phonon Scattering and Dopant‐Induced Deformation Potential Reduction and Lattice Shrink

• Published in: Angewandte Chemie International Edition Vol. 61; no. 35
• Main Authors: Li, Fan, Liu, Xin, Ma, Ni, Chen, Ling, Wu, Li‐Ming
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 26.08.2022
• Edition: International ed. in English
• Subjects: Carrier density; Carrier mobility; Deformation; Dislocation density; Dopants; Grain boundaries; Grain Boundary Scattering; Heat transfer; Low Thermal Conductivity; Optimization; Phonon-Electron Coupling; Phonons; Power factor; Scattering; Thermal conductivity; Thermoelectric materials; Thermoelectricity; Thermoelectrics
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.202208216

We report a Zintl phase thermoelectric material, coarse grain‐In0.99Ga0.01Te, achieving a ZT peak of 1.2 at 648 K and an average ZT=0.8 in 300–650 K, which outperforms all the known InTe‐based materials to date. The synergistic optimization of electronic property and phonon transport are achieved by the purification of grain boundary scattering, together with the Ga‐doping‐induced weak phonon‐electron coupling, which enhances the carrier mobility and carrier concentration simultaneously and consequently gives a remarkably increased power factor of 8.9 μW cm−1 K−2. The DFT phonon calculations indicate the dopant reduces the deformation potential coefficient and induces the lattice shrink, which reduces significantly the acoustic cutoff frequency, and enhances the scattering phase space. Moreover, the bonding hierarchy leads to the dense intragranular dislocation arrays, which suppresses the lattice thermal conductivity further and induces an ultralow lattice thermal conductivity (0.21 Wm−1 K−1). Pure acoustic phonon scattering is obtained in a coarse grain‐In0.99Ga0.01Te‐sample. The vibration anharmonicity is significantly enhanced by the Ga dopant, thus also enhancing the bonding hierarchy leading to a reduced deformation potential coefficient and denser intragranular dislocations. These effects collectively lead to a ZT of 1.2 at 648 K, the highest among its analogues.