High performance thermoelectric materials and devices based on GeTe

Abstract

This review summarizes the past and recent developments in the thermoelectric properties, nano/microstructure modulations, and mechanical and thermal stability of GeTe based materials and thermoelectric devices based on GeTe.

Impact of Coinage Metal Insertion on the Thermoelectric Properties of GeTe Solid-State Solutions

“…The rhombohedral phase is further confirmed by the presence of double reflections 33,37 [ (024) and (220) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 In our experimental conditions, the maximum solubility of silver in the rhombohedral GeTe phase appears to be between 4 and 6 mol%, as a cubic phase (Fm-3m space group; a = 5.9118(9) Å) starts to appear for values of x ≥ 0.06. This secondary cubic phase was identified as (Ag,Ge)Te, as the estimated lattice parameter is smaller than that of undoped cubic GeTe (a = 6,02 Å) 44,70 . Microscopic data also supports the PXRD results (refer ESI † Figure S1).…”

“…The temperature-dependent total thermal conductivity κ total derived from D and C p using equation (5) is presented in Figure 6a. At 773 K, the κ total value for Ge 0 for other GeTe based materials, which was ascribed to the second-order phase transition from rhombohedral to cubic phase 33,36,37,39,44 . This transition temperature decreases from 673 K to 573 K with increase in Ag content from 1 to 6 mol%.…”

“…Other well established classes of high performance materials involving carrier and phonon engineering of GeTe are the so-called TAGS alloys with composition (GeTe) x (AgSbTe 2 ) 1-x exhibiting zT values of more than 1 [42][43][44][45] . Similar values of zT at mid-temperature ranges (600-800 K) were achieved for different Powder X-ray diffraction X-ray diffraction (XRD) patterns were recorded at room temperature in the 2θ range 15-120° with a step size of 0.026° and a scan time per step of 400 s using a PANalytical X'Pert Pro diffractometer (Cu K-L 2,3 radiation, λ = 1.5418 Å, PIXcel 1D detector).…”

Ferroelectric phase transition and the lattice thermal conductivity of Pb1−xGexTe alloys

“…These alloys undergo a soft optical mode transition between the rocksalt and rhombohedral phases as a function of the composition and temperature [23], and have high ZT [19,20,[24][25][26][27]. Our first principles virtual-crystal calculations show that the phase transition minimizes the anharmonic component of κ due to extremely soft optical modes which maximize the anharmonic acoustic-optical coupling, especially for lowfrequency phonons.…”

The Effect of Substitution of Gallium on the Transport Properties of Polycrystalline GeTe

“…However, the high toxicity of Pb precludes the use of Pb‐based materials for practical applications. GeTe based materials have been reckoned very promising for mid‐to‐high temperature TE applications owing to relatively non‐toxic constituents and high efficiencies close to those of Pb‐based materials …”