Improvement Of Thermoelectric Performance Research Articles

Improved Thermoelectric Properties of Selenium Functionalized Pedot

AbstractPolymer‐based chalcogenide composites are gaining attention for thermal energy storage thermoelectric (TE) applications due to their high Seebeck coefficient (S) and electrical conductivity (σ), compared to low thermal conductivity of polymers without electrical optimization. This combination can enhance power factor and ZT while suppressing drawbacks. The energy‐filtering effect of polymer/chalcogenide interfaces may also improve TE performance, further enhancing the potential for improved TE applications. In this work, Poly(3,4‐ethylenedioxythiophene) (PEDOT) was functionalized with selenium (Se), and its structural and thermoelectric (TE) properties were studied. The variations of σ and S, with higher percent of Se content, displays a simultaneous rise in both σ and S values, which is noteworthy. The probable reason behind this increment of both σ and S values is due to the improvement in charge transport in the composites due to a percolating network formed between the Se nanoparticles and PEDOT along with the carrier energy filtering interaction between PEDOT and Se. The highest room temperature ZT value obtained is 0.027 for 82 % of Se content in PEDOT, which is comparable with bulk nanostructured organic‐inorganic hybrid composite materials. This work presents an efficient technique for enhancing the TE properties of polymers through inorganic functionalization.

Enhancing Thermoelectric Performance of n-Type Bi2Te2.7Se0.3 through Incorporation of Amorphous Si3N4 Nanoparticles.

Bi2Te3-based thermoelectric (TE) materials are the state-of-the-art compounds for commercial applications near room temperature. Nevertheless, the application of the n-type Bi2Te2.7Se0.3 (BTS) is restricted by the comparatively low figure of merit (ZT) and intrinsic embrittlement. Here, we show that through dispersion of amorphous Si3N4 (a-Si3N4) nanoparticles both 14% increase in power factor (at 300 K) and 48% decrease in lattice thermal conductivity are simultaneously realized. The increased power factor comes from enhanced thermopower and reduced electrical resistivity while the reduced lattice thermal conductivity originates mainly from scattering of middle- and low-frequency phonons at the incorporated a-Si3N4 nanoparticles. As a result, a large ZTmax = 1.19 (at 373 K) and an average ZTave ∼ 1.12 (300-473 K) with better mechanical properties are achieved for the BTS/0.25 wt % Si3N4 sample. Present results demonstrate that the incorporation of a-Si3N4 is a promising way to improve TE performance.

Enhancement of thermoelectric performance in Mg3(Sb,Bi)2 through engineered lattice strain and controlled carrier scattering

Mg3(Sb,Bi)2 emerges as a promising thermoelectric (TE) material due to its rich elemental composition and high TE performance, offering potential for industrial applications. In this study, we found out that the elevated sintering temperatures can introduce dislocations, vacancies, and nanoscale precipitates in the lattice, inducing desirable lattice strain. Higher lattice strain broadens the phonon dispersion, effectively reducing lattice thermal conductivity. Simultaneously, high-temperature sintering increases grain size, significantly mitigating grain boundary carrier scattering and enhancing carrier mobility. As a result, we observe a 31.4 % increase in lattice strain, a 30 % reduction in lattice thermal conductivity, a 200 % rise in room temperature mobility, ultimately achieving an outstanding figure of merit (zT) of 1.7 at 750 K for Mg3.22Ho0.03Sb1.5Bi0.5. The synergistic effect of engineering lattice strain to minimize lattice thermal conductivity and controlling carrier scattering mechanisms to enhance mobility significantly provides a novel strategy to improve TE performance of Mg3(Sb,Bi)2-based materials.

Structure relations with transport properties in p-type thermoelectric materials: Iron silicides

Understanding the structure and its relations with the transport properties is important for designing a good thermoelectric (TE) material. In this work, we investigate the relationship between those properties of the low-cost and eco-friendly materials, β-Fe1-xMnxSi2 (0≤x≤0.10), prepared by direct arc melting and heat treatment process. The metallic phases (tetragonal α-Fe2Si5 and cubic ε-FeSi) are transformed into the semiconductor phase (orthorhombic β-FeSi2) through heat treatment. The amount of β-FeSi2 significantly decreases at x ≥ 0.09. Mn atoms act as an acceptor and improve the carrier density (nH of holes) but decrease the mobility (μH). By substituting Mn to β-FeSi2, the Seebeck coefficient (S) is more uniform at high temperatures and the electrical resistivity (ρ) effectively decreases, leading to an improvement in the power factor. The thermal conductivity (κ) slightly increases with Mn doping. However, with increasing Mn content, the formation of secondary phases increases, resulting in the reduction of solid solution of Mn in β-phase; therefore, the electrical transport deteriorates. As a result, the optimum doping level for improving TE performance is obtained at x = 0.05 sample, verifying with crystal structure analysis that the optimum doping level is in the range of 0 ≤ x ≤ 0.08 because the amount of semiconducting β-FeSi2 drastically drops at x ≥ 0.09. Our study reveals that by judging the variation of the crystal structures, we could achieve the optimum doping level for improving TE transport properties.

Enhanced Thermoelectric Performance in Ca-doped AgSbTe2

Thermoelectric materials play a crucial role in applications such as recovering waste heat and refrigeration. We report a thermoelectric figure of merit (zT) of 1.17 at 623 K for AgSb1-xCaxTe2, representing a 31% enhancement compared to pristine AgSbTe2. The improved thermoelectric performance arises from enhancements in both the power factor and lattice thermal conductivity. Dopant substitution of element Ca at the Sb site in AgSbTe2 suppresses the formation of Ag2Te and increases the concentration of p-type charge carriers, leading to enhanced electrical transport properties. Additionally, Ca doping introduces solid solution point defects that enhance phonon scattering, consequently reducing the lattice thermal conductivity of the sample. This work demonstrates that a doping effectively modulates the electrical and thermal transport properties of AgSbTe2, thereby realizing improvements in thermoelectric performance.

Multifunctional GeMnTe2 Synergistically Optimizes Thermoelectric Properties of SnTe-In2Te3 Alloys.

SnTe-In2Te3 alloys ensure excellent electrical properties in the whole temperature region due to the resonant level. Nevertheless, temperature-sensitive resonance states and single phonon scattering restrict further improvement of thermoelectric performance. Consequently, it is anticipated that additional electrically independent scattering sources should be introduced to impede phonon transport. Here, the SnTe-In2Te3-GeMnTe2 alloy is prepared by further solidifying cubic GeMnTe2, which demonstrates multiple modulation effects. The highly redissolved Mn2+ promotes the valence band convergence, enhances the Seebeck coefficient at higher temperature, and balances the possible weakened resonance level effect at higher carrier concentrations, and a high average power factor (1.94 mW m-1 K-2) is realized over the entire temperature range. Additionally, compensatory vacancies, substitutions, and Ge/Mn precipitates are easily constructed with GeMnTe2 alloying, leading to a further reduction in lattice thermal conductivity, which reaches κl ∼ 0.6 W m-1 K-1 at 850 K. Ultimately, a high peak zT of ∼1.25 (850 K) and a zTave of 0.72 (300-850 K) are realized in (SnTe)2.91(In2Te3)0.03(Ge0.5Mn0.5Te)1.2, and the maximum thermoelectric conversion efficiency of ∼2.8% (ΔT ∼ 450 K) is achieved. The present results indicate multiple effects of GeMnTe2 in enhancing the thermoelectric performance of SnTe-In2Te3 alloys.

Thermoelectric performance of chalcogenide-free CaAl-layered double hydroxide–antimony trioxide nanowire composites with low thermal conductivity

Thermoelectric (TE) materials have attracted considerable interest for their potential and the figure of merit ZT serves as a crucial metric for evaluating TE performance. Chalcogenide materials, such as tellurium (Te) and selenium (Se), have been favored for high-performance TE applications. However, their toxic nature raises concerns, demanding exploration of non-toxic alternatives suitable for human-contacting devices.This study focused on antimony trioxide (Sb2O3) due to its high Seebeck coefficient and explored the potential of layered double hydroxide (LDH) materials as a non-toxic alternative for efficient TE materials. Composites of Sb2O3 nanowires integrated with 2D CaAl-LDH were synthesized to reduce thermal conductivity and improve TE performance. The composites displayed enhanced electrical conductivity, resulting in a significantly improved power factor. The introduction of CaAl-LDH facilitated the charge carrier transport paths, leading to better electrical performance. Furthermore, the composites exhibited reduced thermal conductivity due to phonon scattering at the heterointerfaces between Sb2O3 and CaAl-LDH. As a result, the Sb2O3/CaAl-LDH_70 composite achieved a maximal ZT value of 0.0485 at 473 K, demonstrating promising potential for LDH-based composites as environmentally friendly TE materials. These findings contribute to sustainable energy conversion technologies, ensuring progress towards more efficient and biocompatible TE materials.

Isovalent co-alloying contributes to considerable improvement in thermoelectric performance of BiSe bulks with weak anisotropy

BiSe with intrinsic low thermal conductivity has considered as a promising thermoelectric (TE) material at nearly room temperature. To improve its low thermoelectric figure of merit (zT), in this work, Sb and Te isovalent co-alloying was performed and significantly optimized its TE property with weakly anisotropic characteristic. After substituting Sb on Bi sites, the carrier concentration is suppressed by introduction of Sb Se site defects, which contributes to the increased absolute value of Seebeck coefficient (|S|). Further co-alloying Te on Se of the optimized composition Bi0.7Sb0.3Se, the carrier concentration increased without affecting the |S| due to the enhanced effective mass, which leads to a highest power factor of 12.8 μW/(cm·K2) at 423 K. As a result, a maximum zT of ∼0.54 is achieved for Bi0.7Sb0.3Se0.7Te0.3 along the pressing direction and the average zT (zTave) (from 300 K to 623 K) are drastically improved from 0.24 for pristine BiSe sample to 0.45. Moreover, an energy conversion efficiency ∼4.0% is achieved for a single leg TE device of Bi0.7Sb0.3Se0.7Te0.3when applied the temperature difference of 339 K, indicating the potential TE application.

Ab initio study of mechanical and thermal properties of GeTe-based and PbSe-based high-entropy chalcogenides

GeTe-based and PbSe-based high-entropy compounds have outstanding thermoelectric (TE) performance and crucial applications in mid and high temperatures. Recently, the optimization of TE performance of high-entropy compounds has been focused on reducing thermal conductivity by strengthening the phonon scattering process to improve TE performance. We report a first-principles investigation on nine GeTe-based high-entropy chalcogenide solid solutions constituted of eight metallic elements (Ag, Pb, Sb, Bi, Cu, Cd, Mn, and Sn) and 13 PbSe-based high-entropy chalcogenide solid solutions: Pb0.99-ySb0.012SnySe1-2xTexSx (x = 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, and y = 0) and Pb0.99-ySb0.012SnySe1-2xTexSx (y = 0.05, 0.1, 0.15, 0.2, 0.25 and x = 0.25). We have investigated the mechanical properties focusing on Debye temperature (ΘD), thermal conductivity (κ), Grüneisen parameter (γα), dominant phonon wavelength (λdom), and melting temperature (Tm). We find that the lattice thermal conductivity is significantly reduced when GeTe is alloyed into the following compositions: Ge0.75Sb0.13Pb0.12Te, Ge0.61Ag0.11Sb0.13Pb0.12Bi0.01Te, and Ge0.61Ag0.11Sb0.13Pb0.12Mn0.05Bi0.01Te. This reduction is due to the mass increase and strain fluctuations. The results also show that Ge0.61Ag0.11Sb0.13Pb0.12Bi0.01Te solid solution has the lowest Young’s modulus (30.362 GPa), bulk and shear moduli (18.626 and 12.359 GPa), average sound velocity (1653.128 m/sec), Debye temperature (151.689 K), lattice thermal conductivity (0.574 W.m–1.K–1), dominant phonon wavelength (0.692 Å), and melting temperature (535.91 K). Moreover, Ge0.61Ag0.11Sb0.13Pb0.12Bi0.01Te has the highest Grüneisen parameter with a reduced and temperature-independent lattice thermal conductivity. The positive correlation between ΘD and κ is revealed. Alloying of PbSe-based high-entropy by Sb, Sn, Te, and S atoms at the Se and Pb sites resulted in much higher shear strains resulted in the reduction of phonon velocity, a reduced ΘD, and a lower lattice thermal conductivity.

Band engineering enhances thermoelectric performance of Ag-doped Sn0.98Se

Ag doping can effectively increase the carrier concentration of p-type SnSe polycrystalline, thereby enhancing the thermoelectric (TE) performance. However, the key role of the transport valence band in Ag-doped SnSe remains unclear. Particularly, understanding the influence of evaluating the optimal balance between band convergence and carrier mobility on weighted mobility is a primary consideration in designing high-performance TE materials. Here, we strongly confirm through theoretical and experimental evidence that Ag-doped Sn0.98Se can promote the evolution of valence bands and achieve band convergence and density of states distortion. The significantly increased carrier concentration and effective mass result in a dramatic increase in weighted mobility, which favors the achievement of superior power factors. Furthermore, the Debye model reveals the reasons for the evolution of lattice thermal conductivity. Eventually, a superior average power factor and average zT value are obtained in the Ag-doped samples in both directions over the entire test temperature range. This strategy of improving TE performance through band engineering provides an effective way to advance TEs.

Synergistic Improvement in Thermoelectric Performance by Forming Environmentally Benign Transition Metal Oxide Composites with Graphite

Synergistic Improvement in Thermoelectric Performance by Forming Environmentally Benign Transition Metal Oxide Composites with Graphite

Enhancing the Thermoelectric Performance of GeSb4Te7 Compounds via Alloying Se.

Ge-Sb-Te compounds (GST), the well-known phase-change materials, are considered to be promising thermoelectric (TE) materials due to their decent thermoelectric performance. While Ge2Sb2Te5 and GeSb2Te4 have been extensively studied, the TE performance of GeSb4Te7 has not been well explored. Reducing the excessive carrier concentration is crucial to improving TE performance for GeSb4Te7. In this work, we synthesize a series of Se-alloyed GeSb4Te7 compounds and systematically investigate their structures and transport properties. Raman analysis reveals that Se alloying introduces a new vibrational mode of GeSe2, enhancing the interatomic interaction forces within the layers and leading to the reduction of carrier concentration. Additionally, Se alloying also increases the effective mass and thus improves the Seebeck coefficient of GeSb4Te7. The decrease in carrier concentration reduces the carrier thermal conductivity, depressing the total thermal conductivity. Finally, a maximum zT value of 0.77 and an average zT value of 0.48 (300-750 K) have been obtained in GeSb4Te5.5Se1.5. This work investigates the Raman vibration modes and the TE performance in Se-alloyed GeSb4Te7 sheddinglight on the performance optimization of other GST materials.

ZnSe Nanoparticles for Thermoelectrics: Impact of Cu-Doping

The present study investigates the impact of copper doping on the thermoelectric properties of zinc selenide (ZnSe) nanoparticles synthesized by the hydrothermal method. Nanoparticle samples with varying copper concentrations were prepared and their thermoelectric performances were evaluated by measuring the electrical transport properties, the Seebeck coefficient, and extracting the power factor. The results demonstrate that the thermoelectric properties of Cu-doped ZnSe nanoparticles are significantly enhanced by doping, mainly as an effect of an improved electrical conductivity, providing a promising avenue for energy applications of these nanomaterials. To gain further insights into the fundamental mechanisms underlying the observed improvements in thermoelectric performance of the samples, the morphological, structural, and vibrational properties were characterized using a combination of scanning electron microscopy, X-ray diffraction, and Raman spectroscopy.

Doping by Design: Enhanced Thermoelectric Performance of GeSe Alloys Through Metavalent Bonding.

Doping is usually the first step to tailor thermoelectrics. It enables precise control of the charge-carrier concentration and concomitant transport properties. Doping should also turn GeSe, which features an intrinsically a low carrier concentration, into a competitive thermoelectric. Yet, elemental doping fails to improve the carrier concentration. In contrast, alloying with Ag-V-VI2 compounds causes a remarkable enhancement of thermoelectric performance. This advance is closely related to a transition in the bonding mechanism, as evidenced by sudden changes in the optical dielectric constant ε∞ , the Born effective charge, the maximum of the optical absorption ε2 (ω), and the bond-breaking behavior. These property changes are indicative of the formation of metavalent bonding (MVB), leading to an octahedral-like atomic arrangement. MVB is accompanied by a thermoelectric-favorable band structure featuring anisotropic bands with small effective masses and a large degeneracy. A quantum-mechanical map, which distinguishes different types of chemical bonding, reveals that orthorhombic GeSe employs covalent bonding, while rhombohedral and cubic GeSe utilize MVB. The transition from covalent to MVB goes along with a pronounced improvement in thermoelectric performance. The failure or success of different dopants can be explained by this concept, which redefines doping rules and provides a "treasure map" to tailor p-bonded chalcogenides.

Enhancing Carrier Mobility and Seebeck Coefficient by Modifying Scattering Factor

AbstractThermoelectric materials possess the potential for refrigeration and power generation due to their ability to directly convert heat and electricity. Carrier mobility and the Seebeck coefficient are key properties of thermoelectric materials. Improving the effective mass is the most effective and frequent way to optimize the Seebeck coefficient. However, carrier mobility deteriorates dramatically with increasing effective mass and thus limits further improvement of thermoelectric performance. Here, the focus is on the importance of modifying the scattering factor (r) to enhance the electrical properties, and it is found that the anisotropic scattering factor enhances the carrier mobility and Seebeck coefficient of anion‐doped n‐type tin selenide crystals along the out‐of‐plane direction, indicating the potential of modifying r to improve electrical properties. Following this strategy, the average dimensionless figure of merit (ZTave) for iodine‐doped SnSe crystals is significantly improved from 0.84 to 1.57 in 300–773 K. The results emphasize the critical role of scattering factor and propose a new perspective for enhancing carrier mobility, providing a novel strategy to optimize thermoelectric performance.

Modulation of Vacancy Defects and Texture for High Performance n-Type Bi2 Te3 via High Energy Refinement.

The carrier concentration in n-type layered Bi2 Te3 -based thermoelectric (TE) material is significantly impacted by the donor-like effect, which would be further intensified by the nonbasal slip during grain refinement of crushing, milling, and deformation, inducing a big challenge to improve its TE performance and mechanical property simultaneously. In this work, high-energy refinement and hot-pressing are used to stabilize the carrier concentration due to the facilitated recovery of cation and anion vacancies. Based on this, combined with SbI3 doping and hot deformation, the optimized carrier concentration and high texture degree are simultaneously realized. As a result, a peak figure of merit (zT) of 1.14 at 323 K for Bi2 Te2.7 Se0.3 + 0.05 wt.% SbI3 sample with the high bending strength of 100 Mpa is obtained. Furthermore, a 31-couple thermoelectric cooling device consisted of n-type Bi2 Te2.7 Se0.3 + 0.05 wt.% SbI3 and commercial p-type Bi0.5 Sb1.5 Te3 legs is fabricated, which generates the large maximum temperature difference (ΔTmax ) of 85 K at a hot-side temperature of 343 K. Thus, the discovery of recovery effect in high energy refinement and hot-pressing has significant implications for improving TE performance and mechanical strength of n-type Bi2 Te3 , thereby promoting its applications in harsh conditions.

In-situ construction of all-scale hierarchical microstructure and thermoelectric properties of (Sr0.25Ca0.25Ba0.25La0.25)TiO3/Pb@Bi composite oxide ceramics

SrTiO3-based oxides have been investigated as a promising n-type thermoelectric material at high temperatures; however, the relatively high thermal conductivity results in inferior thermoelectric performance. The lattice thermal conductivity can be significantly reduced by high-entropy engineering via severe lattice distortion. However, high configuration entropy also causes the deterioration of carrier mobility and restrains electron transport resulting in low electrical conductivity. In this work, the low lattice thermal conductivity of 1.7 W/(m·K) at 1 073 K and significantly improved electrical conductivity of 112 S/cm from 60 S/cm can be achieved in n-type (Sr0.25Ca0.25Ba0.25La0.25)TiO3/Pb@Bi composites ceramics with core-shell grains of all-scale hierarchical microstructure. The effects of the complex microstructure of core-shell grains as well as the precipitated Pb@Bi particles on electrons and phonons transport properties were systematically explored. ZTmax of 0.18 was obtained for the SPS-1200, which was 1.5 times that of pure high-entropy (Ca0.2Sr0.2Ba0.2La0.2Pb0.2)TiO3 samples prepared by a solid-state method. This improvement in thermoelectric performance contributes to the addition of Bi2O3 into the high-entropy (Sr0.2Ca0.2Ba0.2Pb0.2La0.2)TiO3 matrix resulting in multiphase core-shell grain structure combined with well-dispersed nano-sized metal Pb@Bi precipitates in the matrix. This feasible strategy of in-situ constructing all-scale hierarchical nanostructures can also be applied to enhance the performance of other thermoelectric systems.

Ultralow lattice thermal conductivity and promising thermoelectric properties of a new 2D MoW3Te8 membrane

Assembling new van der Waals (vdW) materials is challenging for the development of two-dimensional (2D) function devices. The MoW3X8 membrane (X = Se, Te) is a new 2D TMDs membrane molecule composed of one WX2 monolayer and one WX2-MoX2-WX2 sandwich trilayer. The presence of Mo/W atoms endows the new structure with the bridges between X atoms that connect pairs of MoX2/WX2 monolayers and the terminal sites that produce the van der Waals gap in these layers. The mirror symmetry is broken and the phonon dispersion is suppressed by reducing the dimensionality of the MoW3X8 membrane. In this work, the phonon transport and thermoelectric properties of the MoW3X8 membrane are investigated using first-principles method combined with the semi-classical Boltzmann transport and relaxation time approximation (RTA) theories. It is found that the larger gap between low-frequency and high-frequency optical branches in the membrane prevents atomic vibrations and drastically reduces the phonon velocity in a mid-frequency range below the gap. The low-lying optical and acoustic phonon modes are closely linked in MoW3Te8 membranes, enhancing the phonon–phonon scattering and thereby shortening the phonon relaxation time. These characteristics allow the MoW3Te8 membrane to achieve an extremely low lattice thermal conductivity of 0.49 Wm-1K−1 relative to that of the MoW3Se8 membrane (3.25 Wm-1K−1), which also leads to the improvement in thermoelectric performance of the former one. Besides, the maximum ZT values of 4 (4.5) at 900 K and the carrier concentration of 4 × 1011 cm−2 in the n-type (p-type) MoW3Te8 membrane could be enriched because of the low lattice thermal conductivity.

Direct ink writing of Bi2Te3-based thermoelectric materials induced by rheological design

Waste heat recovery systems built with thermoelectric (TE) materials offer promising means to generate electricity from waste heat directly, if TE materials or devices with controllable shapes are created through direct ink writing. However, the nature of TE inks used for direct ink writing must be modified with appropriate rheology to maintain stability and facilitate extrusion, as well as proper mechanical properties to resist deformation. Here, we report Bi2Te3-based inks modified with additives that allow direct printing of tunable architectures. The polyelectrolyte additives-induced adsorbed layers on the surface of TE particles are shown to significantly improve the stability and viscoelasticity of inks. Besides, the improved inks modified with methylcellulose additives exhibit an apparent enhancement of strength properties, thereby enabling the predesigned shapes to hold the successive layers printed above. Using charge control and framework reinforcement, the Bi2Te3-based inks print a series of architectures with porous structures, which largely reduce thermal conductivities. As a result, our three-dimensional-printed materials display high figures of merit ZT of 0.65 and 0.53 for p- and n-type. This work explores how additives can influence both rheological properties, printability, and microstructures, which pave the way to construct complex architectures and improve TE performance for structural and functional applications.

Enhanced Thermoelectric Performance of NixBi0.5Sb1.5Te3via In Situ Formation of NiTe2 Channels

In an endeavor to develop high figure of merit (ZT) thermoelectric materials for power generation and cooling applications, the in situ nano-inclusion formation led to improvement in thermoelectric performance. Herein, we studied the controlled Ni inclusion in the Bi0.5Sb1.5Te3 (BST) matrix with varying Ni concentrations, that is, NixBi0.5Sb1.5Te3 (x = 0, 0.01, 0.04, and 0.08). Structural and microscopic analyses showed a clear formation of multi-structured p-type Bi0.5Sb1.5Te3 with fine channels of NiTe2 and their interface, which forms a potential barrier of 0.26 eV, giving rise to a carrier filtering effect. The inclusion of optimized Ni concentration, that is, x = 0.04, in NixBi0.5Sb1.5Te3 and formation of NiTe2 channels has resulted in higher electrical conductivity of 900 S/cm and Seebeck coefficient of 210 μV/K simultaneously as compared to pristine BST. Further, Ni0.04Bi0.5Sb1.5Te3 has exhibited a ZT value of 1.4 at 373 K, which is 112% higher than the ZT (∼0.66 @ 373 K) of pristine BST.