Boosting the thermoelectric performance of GeTe by manipulating the phase transition temperature via Sb doping

Abstract

It is well known that the thermoelectric performance of GeTe is difficult to manipulate due to its intrinsic overhigh carrier concentration and phase transition. Herein, we achieve that electrical and...

Outstanding CdSe with Multiple Functions Leads to High Performance of GeTe Thermoelectrics

“…Especially, the characteristic twin peaks of rhombohedral‐GeTe in the range of 2θ = 23°–27° and 2θ = 41°–45° gradually show a merging trend as increasing the fraction of CdSe, which manifests that the cubic nature of samples is elevated. [ 41,42 ] The result is also verified by differential scanning calorimetry tests, as illustrated in Figure S2a in the Supporting Information. The phase transition temperature of CdSe‐alloyed Ge 0.9 Sb 0.1 Te samples, manifesting the crystal symmetry of GeTe, shifts to low temperature range with increasing CdSe content.…”

“…As can be seen from formula (1), there are two mechanisms to increase m * : i) enlarging the band degeneracy ( N V ) including band convergence and activation of multiple bands near Fermi level and ii) increasing a single band effective mass such as band flattening and DOS distortion. [ 8,16,36,41 ] Alloying CdSe has negligible influence on carrier density at lower temperatures in this work, excluding the possibility of multiple bands activation. Therefore, we speculate that the increased m * derives from the band structure evolution upon CdSe alloying, which leads to the increased Seebeck coefficient.…”

“…After optimizing the carrier density of GeTe through counter‐doped Sb, [ 41 ] here, we further investigate the charge and phonon transport properties of Ge 0.9 Sb 0.1 Te with CdSe alloying. Coupling high‐temperature synchrotron radiation X‐ray diffraction (SR‐XRD) results and the electronic band structure calculations, we find that CdSe alloying gives rise to the decrement of the energy offset between the heavy and light valence band and also produces a DOS distortion.…”

General strategies to improve thermoelectric performance with an emphasis on tin and germanium chalcogenides as thermoelectric materials

“…TE properties of GeTe-based materials can be enhanced by tuning the phase transition temperature via doping with Sb. 388 Sb has the advantage to effectively optimize the carrier concentration, as already discussed. Sb-can promote the crystal symmetry of GeTe to enlarge the band degeneracy while flattening the valence band.…”

“…Finally, the peak ZT $ 1.8 at 773 K and a ZT avg $1.1 from 300 K to 773 K were achieved in the Ge 0.9 Sb 0.1 Te sample. 388 When pristine GeTe is doped with Sn-the rhombohedral to cubic structural phase transition temperature is reduced to 557 K. Total thermal conductivity reduces signicantly for Ge 0.9 Sn 0.1 Te near room temperature. 389 For amorphous GeTe, increasing Sn content decreased the band gap, and a PF $ 2.789 Â 10 3 mW m À1 K À2 was achieved at 300 K. For the crystalline lm of GeTe, the PF $ 1.423 Â 10 3 mW m À1 K À2 at 718 K was achieved, as Sndoping increases effective mass in this case.…”