Thermoelectric Zintl Compound In 1-x Ga x Te: Pure Acoustic Phonon Scattering and Dopant-Induced Deformation Potential Reduction and Lattice Shrink.

We report a Zintl phase thermoelectric material, coarse grain-In 0.99 Ga 0.01 Te, 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 ).