High-efficiency Thermoelectric Materials Research Articles

Research on the Basic Properties and Preparation Methods of Heat Conversion Materials

The purpose of this literature review is to discuss the research progress and application prospects of high-efficiency thermoelectric conversion materials. In recent years, high-efficiency thermoelectric materials have garnered extensive attention due to their significant applications in waste heat recovery and energy conversion. This paper reviews various types of thermoelectric materials, including metal chalcogenides, silicides, and skutterudite materials, and analyzes their synthesis methods, properties, and advantages and disadvantages. The findings indicate that chemical vapor deposition (CVD), hydrothermal synthesis, and hot pressing are the primary methods for preparing thermoelectric materials, each with distinct advantages and limitations. Nevertheless, by optimizing the preparation processes and material compositions, high-efficiency thermoelectric materials are poised to play a crucial role in the field of sustainable energy in the future. This review summarizes the key findings of current research and suggests potential directions and challenges for future studies.

In-Plane Overdamping and Out-Plane Localized Vibration Contribute to Ultralow Lattice Thermal Conductivity of Zintl Phase KCdSb.

Zintl phases typically exhibit low lattice thermal conductivity, which are extensively investigated as promising thermoelectric candidates. While the significance of Zintl anionic frameworks in electronic transport properties is widely recognized, their roles in thermal transport properties have often been overlooked. This study delves into KCdSb as a representative case, where the [CdSb4/4]- tetrahedrons not only impact charge transfer but also phonon transport. The phonon velocity and mean free path, are heavily influenced by the bonding distance and strength of the Zintl anions Cd and Sb, considering the three acoustic branches arising from their vibrations. Furthermore, the weakly bound Zintl cation K exhibits localized vibration behaviors, resulting in strong coupling between the high-lying acoustic branch and the low-lying optical branch, further impeding phonon diffusion. The calculations reveal that grain boundaries also contribute to the low lattice thermal conductivity of KCdSb through medium-frequency phonon scattering. These combined factors create a glass-like thermal transport behavior, which is advantageous for improving the thermoelectric merit of zT. Notably, a maximum zT of 0.6 is achieved for K0.84Na0.16CdSb at 712 K. The study offers both intrinsic and extrinsic strategies for developing high-efficiency thermoelectric Zintl materials with extremely low lattice thermal conductivity.

Effect of pore structure on the ionic thermoelectric effect of pure cement paste

Ionic thermoelectric effect based on thermal migration of ion in the pore solution is emerging as a new branch of research on the thermoelectric effect of cement-based materials. However, the dense and tortuous pore structure of the cementitious materials may limit the ionic electrical conductivity and reduce the ionic thermal migration in pore solutions. Therefore, improving the pore structure may be a promising direction to enhance the thermoelectric effect of pore solution in cementitious materials. In this study, the pure cement paste with three water-cement ratios (w/c ratio = 0.3, 0.4, 0.5) and two curing methods (sealed curing and wet curing) are used. The effects of the ion concentration of the pore solution on the electrical conductivity and the Seebeck coefficient are investigated by the treatment of the vacuum saturation and the leaching process of the cement pastes. In addition, the pore structure of the cement paste is measured by mercury intrusion porosimetry (MIP). The effect of pore structure on the ionic thermoelectric effect of the cement pastes is studied. The results show not only the porosity and pore connectivity, but also the higher specific surface area of cement matrix is an important parameter for improving the ionic Seebeck coefficient of cementitious materials. The finer pore distribution in the cement matrix will cause a larger thermoelectric voltage. By improving the pore structure, the power factor (PF) of cement paste has been improved by two orders of magnitude, from 0.0027 μWm−1K−2 to 0.178 μWm−1K−2. The findings of this study can guide further understanding of the ionic thermoelectric effect of cementitious materials and provide a method for enhancing the thermoelectric effect of high-efficiency ionic thermoelectric materials (such as polyelectrolytes and ionic liquid) in cement matrix, which can develop ultra-high performance ionic thermoelectric cement-based materials for zero energy buildings.

Strain-Induced Defect Evolution for the Construction of Porous Cu2-xSe with Enhanced Thermoelectric Performance.

Superionic Cu2-xSe, with disordered and even liquid-like Cu ions, has been extensively studied as a high efficiency thermoelectric material. However, the relationship between lattice stability and microstructure evolution in Cu2-xSe under strain, which is crucial for its application, has seldom been explored in previous research. In this study, we investigate the impacts of hydrostatic compression strain on the microstructural evolution and, consequently, its implications for thermoelectric performance. Molecular dynamics (MD) simulations show that high hydrostatic compression strain could induce local diffusion of Cu ions and Se twin evolution, resulting in the breaking and reforming of Cu-Se dynamic bonds and the unstable Se sublattice. The subsequent annealing process of the destabilized structure promoted Se evaporation from the sublattice and resulted in lotus-seedpod-like pores. The reduced sound velocity and intensified phonon scattering, due to pores, lead to a reduction in the lattice thermal conductivity from 0.44 W m-1 K-1 to 0.24 W m-1 K-1 at 800 K, a decrease of approximately 45%, in the porous Cu1.92Se sample. These findings reveal the relationship between stability and defect evolution in Cu2-xSe under high hydrostatic compression, offering a straightforward strategy of defect engineering for designing unique microstructures by leveraging the instability in superionic conductor materials.

Rb(Zn,Cu)4As3 as a New High-Efficiency Thermoelectric Material.

The thermoelectric performance of RbZn4-xCuxAs3 crystallized in the KCu4S3-type structure was investigated. Samples were synthesized via solid-state reactions, followed by hot pressing. Hole carriers were doped by substituting Zn with Cu until x = 0.02, resulting in an increase of the power factor from 0.049 to 0.52 mW/mK2 at T = 797 K. The lattice thermal conductivity was substantially low, with a value of 1.61 W/mK at T = 312 K, independent of doping. This can be attributed to the large vibration of the Rb atoms, as demonstrated by the neutron diffraction analysis. The maximum dimensionless figure of merit, ZT, was 0.53 at T = 797 K, representing the highest value for the 143-Zintl compounds. The result indicated that the 143-Zintl compounds could be a new class of high-performance thermoelectric materials.

Tweaking the interplay of the layers by substitution in Ca3Co4O9+δ for high efficiency thermoelectric materials

Ca3Co4O9 is a well-known high temperature thermoelectric material owing to its sandwich type layered structure consisting of both conducting and insulating slabs. In the present study we attempt to enhance the electrical conductivity without affecting the thermal conductivity by suitable doping in these layers. Compositions with a general formula Ca3−xSrxCo4−xMgx/2Tix/2O9+δ (0 ≤ x ≤ 0.15) were prepared by conventional solid state method and subjected to routine characterization techniques like XRD, SEM and XPS. Sr substitution in the insulating layer and Mg, Ti substitution in the conductive layer led to a decrease in the electrical resistivity from 17.86 mΩ cm to 9.74 mΩ cm, which resulted in an increase in the power factors. The dimensionless thermoelectric figure of merit ZT is found to be 0.13 at 873 K for x = 0.15, which is ̴2.1 times higher than the parent compound attributed to the excess oxygen in the doped composition.

Enhanced Thermoelectric Transport Properties of n -Type SnSe2 Polycrystalline Alloys by Te Doping

SnSe2, a layered posttransition metal chalcogenide, has attracted attention as a high-efficiency thermoelectric material owing to the intrinsic low thermal conductivity. Herein, a series of Sn S e 1 − x T e x 2 ( x = 0 , 0.025, 0.0375, 0.075, 0.1, and 0.125) samples was synthesized to examine the influence of Te doping on electrical, thermal, and thermoelectric properties of n -type SnSe2 alloys. Interestingly, carrier concentration and mobility were simultaneously increased for x = 0.025 and 0.0375. Therefore, electrical conductivity is increased for x = 0.025 and 0.0375 compared to that for the pristine sample, resulting in power factor increase to 0.25 mW/mK2 for x = 0.025 by 12% at 790 K. However, reductions in the electrical conductivity were observed for the samples with x > 0.0375 due to the decrease in carrier mobility for x > 0.0375 , resulting in the decrease of power factor. The lattice thermal conductivity slightly reduced for the doped samples owing to point defects of Te and vacancies originating from Te doping. Consequently, the thermoelectric figure of merit ( z T ) was increased to 0.45 and 0.49 for Sn(Se1.975Te0.025)2 ( x = 0.025 ) and Sn(Se1.9625Te0.0375)2 ( x = 0.0375 ) samples at 790 K, respectively, which was enhanced by 40% and 53% compared to that for undoped SnSe2. The enhanced electrical transport properties were validated by weighted mobility, density-of-state effective mass, and quality factor, and the reduction of the lattice thermal conductivity is analyzed by the Debye-Callaway model.

Understanding the origins of low lattice thermal conductivity in a novel two-dimensional monolayer NaCuS for achieving medium-temperature thermoelectric applications

Understanding the lattice dynamics from the perspective of chemical bonds and phonon transport is essential for finding and designing high-efficiency thermoelectric (TE) materials and achieving applications. The coexistence of weak chemical bonding and strong phonon anharmonicity is elucidated as the origin of the intrinsically low lattice thermal conductivity by combining the first principles with the Boltzmann transport theory. By utilizing the crystal orbital Hamilton population (COHP) analysis, the weaker Cu-S chemical bonding originating from the filled antibonding orbitals gives rise to the low average phonon group velocity (va). Here, this research also investigates the scattering processes (the out-of-plan acoustic mode (ZA) + optical mode (O) → O (ZA + O → O), the in-plane transverse acoustic mode (TA) + O → O (TA + O → O), and the in-plane longitudinal acoustic mode (LA) + O → O (LA + O → O)), from which we find that 2D NaCuS possesses strong phonon anharmonicity. The low va and strong phonon scattering enable 2D NaCuS to exhibit a low room temperature lattice thermal conductivity (klat) of 1.95 W/mK. Furthermore, our studies demonstrate 2D NaCuS presents a high ZT of 1.44 at 500 K due to the low klat and excellent electronic transport performance. This study demonstrates that 2D NaCuS is identified as a new TE material for promising medium-temperature applications.

New Mineral Names

Abstract This issue of New Mineral Names provides a summary of several new species in the tetrahedrite-group along with examples of how museums are sharing type and cotype specimens. Currently there are approximately 50 sulfosalt mineral species in the tetrahedrite-group that have the general formula M2(A6)M1(B4C2)X3(D4)S1(Y12)S2(Z), with A = Cu+, Ag+, ☐; B = Cu+, Ag+; C = Zn2+, Fe2+, Hg2+, Cd2+, Mn2+, Ni2+, Cu2+, Cu+, Fe3+; D = Sb3+, As3+, Bi3+, Te4+; Y = S2–, Se2–; Z = S2–, Se2–, ☐. All members if the tetrahedrite-group are isometric and have potential applications high efficiency thermoelectric materials. Some the type specimens of tetrahedrite, and others in this review, are shared between museums. Having newly described minerals housed at multiple museums provides easier access to specimens for researchers around the world and serves to preserve these minerals in case of loss at any one the institutions. Here we look at the descriptions of stibiogoldfieldite, graulichite-(La), tennantite-(Cu), wildcatite, ellinaite, paqueite, burnettite, saccoite, and gurzhiite.

Thermoelectric properties of hole-doped CuRhO2 thin films

Design and realization of high-efficiency p-type thermoelectric materials with excellent performance are the demand for integrated thermoelectric components. Compared with single crystal bulk materials, thermoelectric thin films are more suitable for the miniaturization of thermoelectric devices. Here, c-axis oriented CuRh1−xMgxO2 (x = 0, 0.05, and 0.1) thin films were prepared and the thermoelectric properties are reported. The power factor of a p-type 10% Mg-doped CuRhO2 thin film shows a large value of 535.7 μW K–2 m-1 at 300 K. The results suggest that the hole-doped CuRhO2 thin films can be regarded as potential p-type thermoelectric oxide and will pave an avenue to develop Rh-based thermoelectric thin films.

First-principles study on the ultralow lattice thermal conductivity of BiSeI

Thermoelectric materials have received widespread attention for decades. An important way to find high-efficiency thermoelectric materials is to find materials with ultralow thermal conductivity. Here, we have studied the lattice thermal conductivity of the quasi-one-dimensional semiconductor BiSeI through first-principles calculations. It is found that the thermal conductivity of BiSeI has a large anisotropy due to its quasi-one-dimensional structure. Particularly, BiSeI has ultralow lattice thermal conductivities of 0.28 and 0.34 W/m⋅K along the a and c axes at room temperatures. The lattice thermal conductivity of BiSeI along the b axis is also quite low, which is 1.54 W/m⋅K at room temperatures. It is shown that the quasi-one-dimensional crystal structure and heavy element mass of BiSeI result in low phonon group velocities and short phonon lifetimes, which inevitably lead to ultralow thermal conductivity. Our work implies that BiSeI is a potential thermoelectric material if its electric conductivity could be enhanced in experiments.

Investigation of structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te) chalcopyrites semiconductors using the accurate mBJ approach

Ternary chalcopyrites have recently been the focus of scientists due to their optoelectronic and thermoelectric application as solar energy converters, nonlinear optical devices and detectors. In the present study, we used the first principle calculations based on the density functional theory (DFT) to explore the structural, optoelectronic and thermoelectric properties of GaCuX2 (X = S, Se and Te). The electronic band structure, density of states and optical properties were investigated using the modified Becke Johnson (TB-mBJ) approximation. These materials were discovered to be direct band gap semiconductors in this study, which agrees well with previously reported results. When compared to GaCuS2 and GaCuTe2, GaCuSe2 has a smaller gap value, due to the lower chemical bonding nature of Ga and Se atoms. The density of states of these three ternary chalcopyrites, as well as their optical properties including dielectric functions, optical conductivity and absorption coefficient have also been examined and discussed in details. The maximum reflectivity occurs at 13.5 eV, which exists in the ultra-violet region, showing that investigated materials can be employed to shield high frequency ultraviolet radiations. The calculated maximum refractive index static value varies from 1.5 to 5.5 eV, predicting that the materials under consideration can be used in a vast range of optoelectronic applications, especially in the visible range. GaCuS2 shows high refraction among these compounds. Finally, the thermoelectric properties of these materials, such as the Seebeck coefficient, the power factor and figure of merit, are analyzed using the semi-classical Boltzmann theory as executed in the BoltzTraP code. The high Seebeck coefficient and figure of merit values reveal that these systems belong to a new class of high-efficiency thermoelectric materials (TE) for high-temperature application fields. These findings are likely to open up new route for researchers looking into the potential areas of application of these compounds in thermoelectric and optoelectronic devices.

Ag9GaSe6: high-pressure-induced Ag migration causes thermoelectric performance irreproducibility and elimination of such instability

The argyrodite Ag9GaSe6 is a newly recognized high-efficiency thermoelectric material with an ultralow thermal conductivity; however, liquid-like Ag atoms are believed to cause poor stability and performance irreproducibility, which was evidenced even after the 1st measurement run. Herein, we demonstrate the abovementioned instability and irreproducibility are caused by standard thermoelectric sample hot-pressing procedure, during which high pressure promotes the 3-fold-coordinated Ag atoms migrate to 4-fold-coordinated sites with higher-chemical potentials. Such instability can be eliminated by a simple annealing treatment, driving the metastable Ag atoms back to the original sites with lower-chemical potentials as revealed by the valence band X-ray photoelectron chemical potential spectra and single crystal X-ray diffraction data. Furthermore, the hot-pressed-annealed samples exhibit great stability and TE property repeatability. Such a stability and repeatability has never been reported before. This discovery will give liquid-like materials great application potential.

First principle design of new thermoelectrics from TiNiSn based pentanary alloys based on 18 valence electron rule

In this study we have reported electronic structure, lattice dynamics, and thermoelectric (TE) transport properties of a new family of pentanary substituted TiNiSn systems using the 18 valence electron count (VEC) rule. We have modeled the pentanary substituted TiNiSn by supercell approach with the aliovalent substitution, inspite of the traditional isoelectronic substitution. We have performed the detailed analysis of electronic structure, lattice dynamics, and TE transport properties of selected systems from this family. From our calculated band structures and density of states we show that by preserving the 18 VEC through aliovalent substitutions at Ti site of TiNiSn semiconducting behavior can be achieved and hence one can tune the band structure and band gap to maximize the thermoelectric figure of merit (ZT) value. Two approaches have been used for calculating the lattice thermal conductivity (κL), one by fully solving the linearized phonon Boltzmann transport (LBTE) equation from first-principles anharmonic lattice dynamics calculations implemented in Phono3py code and other using Slack’s equation with calculated Debye temperature and Grüneisen parameter using the calculated elastic constant values. At high temperatures the calculated κL and ZT values from both these methods show very good agreement. The calculated κL values decreases from parent TiNiSn to pentanary substituted TiNiSn systems as expected due to fluctuation in atomic mass. The substitution of atoms with different mass creates more phonon scattering centers and hence lower the κL value. The calculated κL for Hf containing systems La0.25Hf0.5V0.25NiSn and non Hf containing system La0.25Zr0.5V0.25NiSn calculated from Phono3py (Slack’s equation) are found to be 0.37 (1.04) and 0.16 (0.95) W/mK, at 550K, respectively and the corresponding ZT value are found to be 0.54 (0.4) and 0.77 (0.53). Among the considered systems, the calculated phonon spectra and heat capacity show that La0.25Hf0.5V0.25NiSn has more optical-acoustic band mixing which creates more phonon–phonon scattering and hence lower the κL value and maximizing the ZT. Based on the calculated results we conclude that one can design high efficiency thermoelectric materials by considering 18 VEC rule with aliovalent substitution.

Thermal transport properties for unveiling the mechanism of BiSbTe alloys in thermoelectric generation: A glance from synchrotron radiation Bi L3-XAFS

For thermal to electric energy conversion, designing a high efficiency thermoelectric material entails simultaneously optimizing multiple properties of the material. Although it may appear simple to increase electrical power while minimizing thermal losses, the complicated link between these parameters makes optimization difficult, necessitating a more sophisticated approach. The one-pot zone melting method was used to fabricate undoped and Sb doped Bi2Te3 (Bi2−xSbxTe3; x = 0.0, 0.2, 0.6, and 1.0) in pellets form. X-ray diffraction (XRD), Raman and selected area electron diffraction (SAED) revealed rhombohedral polycrystalline nature and a unique high intensity of the Eg2 optical mode according to the nanosheet nature of the alloys as observed in the scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images. Besides, High Resolution TEM (HRTEM) micrographs depicted twin boundary effect with an angle of 120° for Bi1.8Sb0.2Te3 alloys, which may enhance the electronic transport and the thermoelectric properties of the fabricated compounds. To obtain selective and detailed local structural information of Bi2−xSbxTe3 matrix, synchrotron radiation-based X-ray absorption spectroscopy (XAS) measurements were performed at around Bi L3-edge. A significant influence of the Sb/Bi substitution on the local/atomic structure was observed through the gradual elongation of the average in-plane Bi–Sb bond distance. The combination of different off-line structural characterization techniques such as XRD, Raman, SEM, and HRTEM with synchrotron based XAS technique and Laser-Beam Deflection Spectroscopy (BDS) is necessary to fully describe the samples nature and to get average crystal, morphological and local/electronic structural information for unveiling the BiSbTe mechanism in thermoelectric generation.

Thermoelectric performance in the binary semiconductor compound A2Se2(A = K, Rb) with host-guest structure

The host-guest structure compounds are potential candidates for high-efficiency thermoelectric (TE) materials because of their good electronic transport combined with ultralow thermal conductivity. In this paper, we theoretically investigate TE transport properties of the hexagonal ${A}_{2}{\mathrm{Se}}_{2}\phantom{\rule{4pt}{0ex}}(A$ = K, Rb) with strongly quartic anharmonicity based on an incorporation of first-principles calculations with self-consistent phonon theory and Boltzmann transport equations. The calculation results reveal that ${A}_{2}{\mathrm{Se}}_{2}\phantom{\rule{4pt}{0ex}}(A$ = K, Rb) have ultralow lattice thermal conductivities ${\ensuremath{\kappa}}_{L}$, e.g., 0.30--0.$34{\mathrm{W}\phantom{\rule{0.16em}{0ex}}\mathrm{m}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{K}}^{\ensuremath{-}1}$ at room temperature, which are only one third of quartz glass. The calculated results indicate that the coexistence of small phonon lifetime ${\ensuremath{\tau}}_{\mathrm{ph}}$ and phonon group velocity ${\ensuremath{\upsilon}}_{\mathrm{ph}}$ is the reason for the ultralow ${\ensuremath{\kappa}}_{L}$ in these two host-guest structure materials. Additionally, due to the anisotropic electronic structure, that is, the coexistence of high dispersion and flat band edges, these two materials capture a high TE power factor along the $c$ axis. As a consequence, the anomalous high $\mathit{ZT}$ values of 2.95 and 2.17 at 500 K along the $c$-axis direction are captured in $n$-type ${\mathrm{K}}_{2}{\mathrm{Se}}_{2}$ and ${\mathrm{Rb}}_{2}{\mathrm{Se}}_{2}$, which break the long-term record of $\mathit{ZT}\phantom{\rule{4pt}{0ex}}<2$ in most TE materials reported so far. These findings reveal that ${A}_{2}{\mathrm{Se}}_{2}\phantom{\rule{4pt}{0ex}}(A$ = K, Rb) has broad prospects in TE applications.

Enhancing thermoelectric performance of K-doped polycrystalline SnSe through band engineering tuning and hydrogen reduction

High-efficient and environment-friendly thermoelectric materials have attracted much attention. The single crystal tin selenide (SnSe) has a record high thermoelectric figure of merit (ZT) of 2.6 at ~800 K. Polycrystalline SnSe has better mechanical-strength but inferior ZT values than the single crystal, attribute to the paradoxically higher thermal conductivity (κ). In this work, we synthesized KxSn1−xSe (x = 0, 0.01, 0.02, 0.03 and 0.04) by doping K2CO3. A large number of point defects and dislocations generated with CO2 volatilization, which possibly reduces κ. Based on this process, the KxSn1−xSe powders were followed by the hydrogen reduction with 4% H2 − 96% Ar atmosphere to reduce tin oxide and potassium oxide which have high κ. These strategies lead to an ultra-low κ 0.32 Wm−1K−1 in K0.03Sn0.97Se at 798 K. The effects of K doping on electronic transport performance of SnSe were studied by density functional theory calculation and experimental measurement. Doing K can narrow the band gap, increase hole concentration and enhance the electrical conductivity (σ) of SnSe. At 298 K, the σ of KxSn1−xSe increased by more than 2.5 times compared with the pristine SnSe. In high temperature region (623 K< T < 823 K), the σ is mainly affected by thermal excitation. High doping level of K (x = 0.03 and 0.04) suppresses the thermal excitation and limits the maximum of ZT. As the result, A high ZT of 1.06 is obtained at 798 K from K0.01Sn0.99Se perpendicular to the pressing direction, which is 103.8% larger than that of pristine SnSe. In addition, the hot-pressing polycrystalline KxSn1−xSe remains obvious lamellar morphology and show anisotropy. The σ and κ of KxSn1−xSe samples perpendicular to the pressure direction are much higher than those of the samples parallel to the pressure direction. This anisotropy decreases with the increasing K content.

First-principles calculations to investigate Zr substitution enhanced thermoelectric performance of p-type ZrxHf1−xCoBi (x = 0,0.25,0.5,0.75,1) compounds

Based on the first-principle calculation and semi-classical Boltzmann transport theory, the electronic structures and thermoelectric properties of Hf1−xZrxCoBi (x=0,0.25,0.5,0.75,1) compounds have been systematically investigated. These compounds possess narrow bandgaps and they are thermodynamically stable. The low frequency optical branches couple with the acoustic modes in the Zr doped compounds, which highly enhance the phonon scattering. The Zr substitutions hardly reduce the power factors when x=0.25 and 0.75, but substantially reduce the thermal conductivity and thus, improve the figure of merit. The predicted ZT of p-type Hf0.75Zr0.25CoBi and Hf0.25Zr0.75CoBi can reach up to 2.74 and 2.59 at 1200 K, which is much larger than that of the pure HfCoBi compound. This work implies that Hf0.75Zr0.25CoBi and Hf0.25Zr0.75CoBi are promising high-efficiency thermoelectric materials.

Iterative design of a high zT thermoelectric material

Designing a high efficiency thermoelectric material for thermal to electric energy conversion means simultaneously optimizing multiple properties of the material. Although it might seem straightforward to maximize the electrical power and minimize thermal losses, the convoluted relationship between these properties makes optimization complex, requiring a more sophisticated algorithm. The Accelerated Insertion of Materials (AIM) methodology developed to engineer the mechanical properties of complex multiphase steel alloys provides a framework for optimization that can be applied to engineer the thermal and electrical transport properties of a multiphase thermoelectric material. The AIM methodology can be utilized in creating a high figure of merit (zT) material by considering the effects of each structural parameter, such as grain size and grain boundary properties, precipitate volume fraction, and doping and defect concentration of the matrix phase on the zT of the material using a variety of analytical models. The combination of these models provides a way to accelerate the design of high zT materials.

Giant Thermoelectric Seebeck Coefficients in Tellurium Quantum Wires Formed Vertically in an Aluminum Oxide Layer by Electrical Breakdown.

High efficiency thermoelectric (TE) materials still require high thermopower for energy harvesting applications. A simple elemental metallic semiconductor, tellurium (Te), has been considered critical to realize highly efficient TE conversion due to having a large effective band valley degeneracy. This paper demonstrates a novel approach to directly probe the out-of-plane Seebeck coefficient for one-dimensional Te quantum wires (QWs) formed locally in the aluminum oxide layer by well-controlled electrical breakdown at 300 K. Surprisingly, the out-of-plane Seebeck coefficient for these Te QWs ≈ 0.8 mV/K at 300 K. This thermopower enhancement for Te QWs is due to Te intrinsic nested band structure and enhanced energy filtering at Te/AO interfaces. Theoretical calculations support the enhanced high Seebeck coefficient for elemental Te QWs in the oxide layer. The local-probed observation and detecting methodology used here offers a novel route to designing enhanced thermoelectric materials and devices in the future.