Enhancement of Thermoelectric Performance in Na-Doped Pb_0.6Sn_0.4Te_0.95–xSe_xS_0.05 via Breaking the Inversion Symmetry, Band Convergence, and Nanostructuring by Multiple Elements Doping

Abstract

Topological insulators have attracted much interest in topological states of matter featuring unusual electrical conduction behaviors. It has been recently reported that a topological crystalline insulator could exhibit a high thermoelectric performance by breaking its crystal symmetry via chemical doping. Here, we investigate the multiple effects of Na, Se, and S alloying on thermoelectric properties of a topological crystalline insulator PbSnTe. The Na doping is known to be effective for breaking the crystalline mirror symmetry of PbSnTe. We demonstrate that simultaneous emergence of band convergence by Se alloying and nanostructuring by S doping enhance the power factor and decrease lattice thermal conductivity, respectively. Remarkably, the high power factor of 22.3 μW cm K at 800 K is achieved for Na 1%-doped PbSnTeSeS mainly due to a relatively high Seebeck coefficient via band convergence by Se alloying as well as the suppression of bipolar conduction at high temperatures by the increase of energy band gap. Furthermore, the lattice thermal conductivity is significantly suppressed by PbS nanoprecipitates without deteriorating the hole carrier mobility, ranging from 0.80 W m K for PbSnTe to 0.17 W m K at 300 K for PbSnTeSeS. As a result, the synergistically combined effects of breaking the crystalline mirror symmetry of topological crystalline insulator, band convergence, and nanostructuring for PbSnTeSe S ( x = 0, 0.05, 0.1, 0.2, and 0.95) give rise to an impressively high ZT of 1.59 at 800 K for x = 0.05. We suggest that the multiple doping in topological crystalline insulators is effective for improving the thermoelectric performance.

Charge and phonon transport in PbTe-based thermoelectric materials

“…94 The nano-precipitates with coherent or semicoherent interfaces have been widely observed in PbTe-PbQ (Q = Se, S) solid solutions. 61,63,95,96 Interestingly, the shapes and sizes of nano-precipitates in a given thermoelectric system are also sensitive to the processing parameters during synthesizing, such as cooling rate, annealing temperature and annealing time, etc. 53,97 Internal structure designs in PbTe-based thermoelectric materials Most of superior PbTe-based thermoelectric materials are obtained by reducing lattice thermal conductivity through scattering phonons via designing special microstructures.…”

“…At last, a discussion of future possible strategies is proposed to aim at further enhancing the thermoelectric performance in PbTe-based materials. PbTe-Ge:Na, 101 (2) PbTe:(Na, Bi), 102 (3) PbTe-Sn:(Ag, Sb), 103 (4) PbTe-Mn:Na, 104 (5) PbTe-Se:K, 105 (6) PbTe-Ca:Na, 91 (7) PbTe-Cd:Na, 92 (8) PbTe-S:K, 61 (9) PbTe:Na, 106 (10) PbTe:Na (Nano-precipitates), 107 (11) PbTe-Ge, 108 (12) PbTe-Se-S:Na, 109 (13) PbTe-Hg: Na, 110 (14) PbTe:Tl, 64 (15) PbTe-Sn-Se-S: Na, 95 (16) PbTe-Yb:Na, 111 (17) PbTe-Se:Na, 62 (18) PbTe-Mn-Sr:Na, 112 (19) PbTe-Mg:Na, 60 (20) PbTe-Eu:Na, 113 (21) PbTe-Sr:Na, 59 (22) PbTe-S:Na, 63 (23) PbTe-Sr:Na (Non-equilibrium); 53 d peak ZT values as a function of optimized carrier density in n-type PbTe systems: (1) PbTe-Se:Cr, 114 (2) PbTe-Se-S:I, 115 (3) PbTe-NaCl, 116 (4) PbTe-Zn:I, 117 (5) PbTe-Cd:I, 118 (6) PbTe-Sn-Se:I, 119 (7) PbTe-Mg:I, 120 (8) PbTe-Se-S:Cl, 121 (9) PbTe:Cd, …”

Approaching Topological Insulating States Leads to High Thermoelectric Performance in n-Type PbTe

“…When Sn content increases to 0.40 in Pb 0.6 Sn 0.4 Te , and Sn content to ∼0.23 in Pb 0.77 Sn 0.23 Se, the band gap reaches close to zero, indicating that Se alloying could promote the band inversion of PbTe. During the process of band inversion, approaching topological insulating states, the electronic band structures will become sharper, which can cause a smaller carrier effective mass and a higher carrier mobility. − Moreover, nanostructures are expected to be avoided due to complete solubility of Sn and Se in the PbTe matrix, which also could maintain high carrier mobility. In this work, we found that the electronic band inversion (approaching topological insulating states) leads to high-performance n-type PbTe.…”

Facile Synthesis of Zn/N‐doped CuO and Their Application in Oxygen Evolution Reaction

“…All actual metal oxides contain some defects that have a great influence on the properties of materials due to thermal equilibrium and kinetics during the reaction Specifically, the defect structure of cubic crystalline phase can lead to the depletion of the ion loader and the cross diffusion of the elements, that is, the concentration gradient and interaction between the ion defects and the charge carriers …”

“…‐ There are many chemical synthesis methods carried out to realize elements doping of materials, for example, Ginting and his co‐workers successfully synthesized Na‐doped Pb 0.6 Sn 0.4 Te 0.95−x Se x S 0.05 by using PbSe and PbS as precursors and mixing with Pb, Te, Sn and Na. They found that Na doping played an important role in breaking the crystalline mirror symmetry of Pb0.6Sn0.4Te . Not long ago, Bao et.…”