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

Abstract

A comprehensive study on the thermoelectric effect of Ag substitution in GeTe solid solutions, a congenital base for high efficient TAGS-m [(GeTe) m (AgSbTe 2 ) 100-m ] thermoelectric materials, was performed. First-principles calculations were carried out to probe the changes arising from doping on the electronic band structure of GeTe, which exhibits a rhombohedral (r) structure at temperatures lower than 700 K. Aliovalent Ag substitution in GeTe increases the hole concentration and decreases the thermoelectric figure of merit (zT) due to the reduction of the Seebeck coefficient, which is ascribed mainly to the lowering of the Fermi level together with the loss of band degeneracy. Band structure and effective mass calculations of these doped materials also point to a soaring contribution from several hole pockets in the valence band. First-principles calculations carried out with two other group-11 transition metals (Cu, Au) reveal that silver substitution has the lowest impact on the thermopower of r- Page 1 of 32 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 60 2 GeTe. A mean zT of ∼0.85 at 773 K is achieved for Ge 1-x Ag x Te (x ≤ 0.04) solid solutions. The study highlights the limits in doping just a coinage metal to GeTe and recapitulates the need for pair substitution to enhance the thermoelectric properties of GeTe-based solid-state solutions.

Manipulating the Ge Vacancies and Ge Precipitates through Cr Doping for Realizing the High‐Performance GeTe Thermoelectric Material

“…Temperature‐dependent thermoelectric transport properties for Cr doping samples Ge 1– x Cr x Te ( x = 0, 0.02, 0.03, 0.04, and 0.05): a) electrical resistivity, b) Seebeck coefficient, c) power factor, d) total thermal conductivity, e) lattice thermal conductivity of Ge 1– x Cr x Te (this work) in comparison with reported Ti x Ge 1– x Te, [ 52 ] In x Ge 1– x Te, [ 59 ] Mn x Ge 1– x Te, [ 43 ] Ag x Ge 1– x Te, [ 60 ] and f) figure of merit (ZT).…”

Effect of the Processing Route on the Thermoelectric Performance of Nanostructured CuPb18SbTe20

“…where e is the electronic thermal conductivity and L is the Lorenz number computed by the condensed version of Single Parabolic Band model with acoustic phonon scattering (SPB-APS), 20,67 as in equation (7) =…”

“…(i) quantum confinement of electron charge carriers; 8 (ii) synergistic nano-structuring; [9][10][11][12][13] (iii) nanoinclusions, which enable acoustic phonon scatterings; 14,15 (iv) electron filtering; 16 (v) convergence of electronic band valleys; [17][18][19][20] (vi) fostering resonant levels by impurities inside the valence band; 21 (vii) alloying to create point defects; [22][23][24] (viii) complex crystal structures like skutterudites, 25,26 Zintl compounds, 27,28 hetero-structured superlattice thin-films; 29 (ix) semi-conducting glasses, [30][31][32][33][34] and (x) utilization of magnetism, [35][36][37][38] for instance.…”

High‐Performance GeTe‐Based Thermoelectrics: from Materials to Devices

“…Table 4 compares different GeTe‐based thermoelectric materials synthesized by different method, including high‐vacuum and high‐temperature melting [ 80,127,128,140,144–147 ] or solid‐state reaction [ 148,149 ] method. The high temperature can secure sufficient reaction of precursors to form high‐purity and composition‐homogeneous solid solutions.…”

“…To synthesize nanosized GeTe, high‐energy ball milling (also known as mechanical alloying) has been introduced. [ 144,148 ] The highly localized energy and fast reaction process during ball milling process can minimize the crystal growth and refrain the crystal size of as‐synthesized GeTe. [ 144 ] In addition, GeTe thin film has also been prepared by magnetron sputtering method.…”