Band structure engineering in Sn_1.03Te through an In-induced resonant level

Abstract

In substitution in Sn1.03Te forms a resonant level that strongly affects the thermoelectric properties at high temperatures.

Physical Insights on the Lattice Softening Driven Mid‐Temperature Range Thermoelectrics of Ti/Zr‐Inserted SnTe—An Outlook Beyond the Horizons of Conventional Phonon Scattering and Excavation of Heikes’ Equation for Estimating Carrier Properties

“…The XRD patterns of these SPS processed samples can be well indexed to the NaCl-type face-centered cubic (fcc) SnTe phase (Fm-3m, space group n° 225). Also observed is the minor proportion of metallic Sn phase (I4/mmm, space group n°141), as in agreement with the previous studies, [59] is known to be segregated at the grain boundaries. [60] Other secondary phases start to appear at higher content of Ti or Zr (x ≥ 0.05).…”

“…The optimized single (Ti/Zr) doping and codoping (Ti-Mn/Zr-Mn) enabled an improvement in the electrical transport of SnTe, thanks to an amalgamation of factors, such as i) bolstering of weighted mobility by striking the suitable trade-off between the effective mass, carrier concentration and carrier mobility, ii) bringing Figure 20. Thermoelectric performance of optimized Ti//Zr doped SnTe in this work is compared with other reported SnTe dopants like Ga, [79] Cu, [113] In, [59] Mg, [40] V, [50] and the Ti-Mn/Zr-Mn codoped SnTe in this work is compared with other reported SnTe codopants such as In-Se, [114] In-Mn, [27] Bi-Pb, [28] Sb-In, [112] Ca-I. [65] in the mixed carrier scattering mechanisms, iii) manipulating the electronic band structure by increasing the density of states (with Ti), engineering the carrier-pockets to raise the effective mass (with Zr), and corrugated flat-bands yielding multiple Fermi-surfaces, besides opening up the forbidden energy gap and reducing the energy separation between the light and heavy hole valence bands (with codoping), and iv) feasible interaction between the carriers and magnetic moments (with Mn-codoping to Ti/Zr), and more importantly (v) these transition dopants (Ti/Zr/Mn), when added to SnTe, softened the chemical bonds, which resulted in high anharmonicity with a decrease in the elastic moduli (Shear and Young's modulus) and an increase in the internal strain-fields that simultaneously changed the phonon group velocity (speed of sound) and induced phonon scattering.…”

“…Synthesis: The SnTe-based samples were synthesized via a vacuumsealed tube melt processing route. It must be noted that, just like in many other SnTe-based materials that are reported so far, the selfcompensated Sn 1.03-x M x Te (M = dopant) nominal composition was adopted here to reach the actual stoichiometry and to optimize their charge carrier concentration, [37,40,59,64,79,86] that is, to compensate for the inherent nature of SnTe to have Sn vacancies (Sn 1−x Te). From the crystallographic point of view, it was not possible to have excess Sn in the structure (SnTe).…”

“…Similar to that of Zr-doping, the apparition of the secondary phase at higher Ti-content confirms that the solubility limit of Ti in SnTe is crossed at x = 0.05. This solubility limit of x ≤ 0.04 for Ti or Zr in SnTe is much higher when compared to dopants such as Co or Ni, [62] and similar to that of dopants such as Ge, [62] In, [59] and lower compared to dopants such as Sb, [63] Mn, [27] Ca. [37] A representative SEM-EDX chemical/elemental mapping of the Sn 0.98 Zr 0.02 Te sample presented in Figure 4 reveals the compositional micro-homogeneity, particularly the dopant's uniform distribution in the SnTe material without any aggregation.…”

Low-temperature transport properties of n-type layered homologous compounds Bi8−xSbxSe7

“…1,2 The interdependence of , and via the carrier concentration makes the optimization of the values a challenging undertaking. Band structure engineering, which aims to optimize the power factor 2 / through band convergence or resonant levels, [3][4][5][6][7][8][9][10] and searching for materials exhibiting very low values, [10][11][12][13][14][15][16][17][18][19][20] are the two general strategies pursued to mitigate these difficulties. Along this second line of research, cage-like structures and materials showing a high degree of lattice anharmonicity or structural complexity are prominent examples of compounds sought after in thermoelectricity.…”