Rare-Earth Nd Inducing Record-High Thermoelectric Performance of (GeTe) 85 (AgSbTe 2 ) 15

As a promising midtemperature thermoelectric material with both higher thermoelectric performance and mechanical property, Tellurium Antimony Germanium Silver (TAGS-x), written as (GeTe)x(AgSbTe2)1-x, especially (GeTe)0.85(AgSbTe2)0.15 (TAGS-85), has attracted wide attention. Herein, we innovatively use Nd doping to synergistically decrease the carrier concentration to the optimal level leading to enhanced dimensionless figure of merit, zT. Our density-functional theory calculation results indicate that Nd-doping reduced carrier concentration should be attributed to the enlargement of band gap. The optimized carrier concentration results in an ultrahigh power factor of ~32 μW cm-1 K-2 at 727 K in Ge0.74Ag0.13Sb0.11Nd0.02Te. Simultaneously, the lattice thermal conductivity of Ge0.74Ag0.13Sb0.11Nd0.02Te retained as low as ~0.5 at 727 K. Ultimately, a record-high zT of 1.65 at 727 K is observed in the Ge0.74Ag0.13Sb0.11Nd0.02Te. This study indicates rare-earth Nd doping is effective in boosting the thermoelectric performance of TAGS-85 and approached a record-high level via synergistic effect.