P-type Thermoelectric Materials Research Articles

Impact of Lu-Substitution in Yb14-xLuxZnSb11: Thermoelectric Properties and Oxidation Studies.

Yb14ZnSb11 is one of the newest additions to the high-performance Yb14MSb11 (M = Mn, Mg, and Zn) family of p-type high-temperature thermoelectric materials and shows promise for forming passivating oxide coatings. Work on the oxidation of rare earth (RE)-substituted Yb14-xRExMnSb11 single crystals suggested that substituting late RE elements may form more stable passivation oxide coatings. Yb14-xLuxZnSb11 (x = 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7) samples were synthesized, and Lu-substitution's effects on thermoelectric and oxidation properties are investigated. The solubility of Lu within the system was found to be quite low with xmax ∼ 0.3; samples with x > 0.3 contained impurities of LuSb. Goldsmid-Sharp band gap estimations show that introducing Lu reduces the apparent band gap. Because of this, the Lu-substituted samples show a reduction in the maximum Seebeck coefficient, decreasing the high-temperature zT. This contrasts with the impact of Lu3+ substitution in Yb14MnSb11, where the addition of Lu3+ for Yb2+ results in increases in both resistivity and the Seebeck coefficient. Oxidation of the x = 0.3 solid solution was studied by thermogravimetric- differential scanning calorimetry , powder X-ray diffraction, scanning electron microscopy-energy-dispersive spectroscopy, and optical images. The samples show no mass gain before 785 K, and ensuing oxidation reactions are proposed. At the highest temperatures, significant amounts of Yb14-xLuxZnSb11 remained beneath an oxide coating, suggesting that passivation may be achievable in oxygen environments.

Power factor enhancement of β-Zn4Sb3-InSb composites via arrays of p-n junction: Mixing p-type and n-type thermoelectric materials

The lead-free and abundantly available nature of β-Zn4Sb3 makes it a promising thermoelectric material for mid-high temperature applications. We produce composites by embedding 1 wt %, 3 wt %, and 5 wt % of n-type InSb into the p-type β-Zn4Sb3 host, enhancing both electrical conductivity and thermopower. At 600 K, the electrical resistivity decreases to 55 μΩ-m from 71 μΩ-m for the β-Zn4Sb3 host. Surprisingly, the thermopower of the β-Zn4Sb3/3 wt % InSb composite increases to 209 μV/K from 180 μV/K for the β-Zn4Sb3 host, contrary to expectations. This enhancement can be attributed to p-n junctions between the p-type β-Zn4Sb3 and n-type InSb. The power factor of the β-Zn4Sb3/3 wt % InSb composite increased to 787 μW/mK2 from 452 μW/mK2 for the β-Zn4Sb3 host. Despite higher thermal conductivity, the β-Zn4Sb3/3 wt % InSb composite achieved the highest zT value of ∼0.67 at around 600 K, 67.5 % higher than the β-Zn4Sb3 host's zT value of 0.40.

Thermoelectric properties of cement composite analogues from first principles calculations

Buildings are responsible for a considerable fraction of the energy wasted globally every year, and as a result, excess carbon emissions. While heat is lost directly in colder months and climates, resulting in increased heating loads, in hot climates cooling and ventilation is required. One avenue towards improving the energy efficiency of buildings is to integrate thermoelectric devices and materials within the fabric of the building to exploit the temperature gradient between the inside and outside to do useful work. Cement-based materials are ubiquitous in modern buildings and present an interesting opportunity to be functionalized. We present a systematic investigation of the electronic transport coefficients relevant to the thermoelectric materials of the calcium silicate hydrate (C-S-H) gel analogue, tobermorite, using Density Functional Theory calculations with the Boltzmann transport method. The calculated values of the Seebeck coefficient are within the typical magnitude (200-600 μ V/K) indicative of a good thermoelectric material. The tobermorite models are predicted to be intrinsically p-type thermoelectric material because of the presence of large concentration of the Si-O tetrahedra sites. The calculated electronic figure of merit, ZT, for the tobermorite models have their optimal values of 0.983 at (400 K and 1017 cm−3) for tobermorite 9 Å, 0.985 at (400 K and 1017 cm−3) for tobermorite 11 Å and 1.20 at (225 K and 1019 cm−3) for tobermorite 14 Å, respectively.

First-principles study of wrinkled SnTe monolayer as p-type thermoelectric material

Tin telluride compounds are promising thermoelectric (TE) materials on account of the excellent electronic and thermal transport properties. The present work focuses on examining the TE performance of a two-dimensional wrinkled SnTe monolayer by employing the first-principles calculations and Boltzmann transport theory. The SnTe monolayer demonstrates high mechanical, dynamic and thermal stabilities, which have been thoroughly investigated using the elastic modulus, formation energy and ab initio molecular dynamics simulations. The lattice thermal conductivities of the SnTe monolayer along the zigzag- and armchair-direction are 11.29 and 12.40 W/mK at 300K, respectively. Due to the large Grüneisen parameters, short phonon relaxation time and low phonon group velocity, the p-type SnTe monolayer exhibits high TE performance at 900 K, as characterized by a high ZT of 1.44 along the zigzag-direction. Our present study not only offers valuable insights into the TE properties of the wrinkled SnTe monolayer, but also sheds some light on the theoretical designing of the novel SnTe-based material for TE applications.

The filled tetrahedral compound NaZnP with strong quartic anharmonicity and good thermoelectric properties

Based on first-principles calculations, self-consistent phonon (SCP) theory, and the Boltzmann transport equation, we investigate the thermal transport and thermoelectric properties of the Nowotny-Juza filled tetrahedral compound NaZnP. The effects of anharmonic phonon renormalization and four-phonon scattering on the heat transport of NaZnP are also considered. The weak binding and rattling-like vibrational behavior of Na atoms lead to strong lattice anharmonicity, and the results show that NaZnP has low lattice thermal conductivity. Furthermore, the coexistence of high dispersion and high degeneracy of valence band maxima leads to high power factor under p-type doping. The combination of low lattice thermal conductivity and good electrical transport properties results in high thermoelectric performance. This indicates that NaZnP is a promising p-type high-temperature thermoelectric material.

High-performance Sb2Si2Te6 thermoelectric device

High-performance thermoelectric (TE) devices are promising for waste-heat recovery and power generation. Recently, Sb2Si2Te6 has been demonstrated as a promising p-type TE material with high performance and low cost. However, Sb2Si2Te6-based TE devices have not yet been fabricated. The performance of TE devices depends on not only TE materials, but also electrode materials and inner interfaces. Herein, we utilize the high throughput strategy to screen the appropriate electrode material and find that cobalt exhibits a low contact resistance (2.47 μΩ cm−2) and a high shear strength (18.03 MPa). Furthermore, we successfully fabricate one eight-couple Sb2Si1.99Ge0.01Te6 (p-type)/Yb0.3Co4Sb12 (n-type) TE module with optimized geometric parameters by the finite element method. The module exhibits a high output power density (0.92 W cm−2) and a decent energy conversion efficiency (4.2%) under a temperature difference of 500 K. Our studies will promote further development of Sb2Si2Te6 materials and Sb2Si2Te6-based devices.

Change of Conduction Mechanism in Polymer/Single Wall Carbon Nanotube Composites upon Introduction of Ionic Liquids and Their Investigation by Transient Absorption Spectroscopy: Implication for Thermoelectric Applications.

Polymer composites based on polycarbonate (PC) and polyether ether ketone (PEEK) filled with single-walled carbon nanotubes (SWCNTs, 0.5-2.0 wt %) were melt-mixed to investigate their suitability for thermoelectric applications. Both types of polymer composites exhibited positive Seebeck coefficients (S), indicative for p-type thermoelectric materials. As an additive to improve the thermoelectric performance, three different ionic liquids (ILs), specifically THTDPCl, BMIMPF6, and OMIMCl, were added with the aim to change the thermoelectric conduction type of the composites from p-type to n-type. It was found that in both composite types, among the three ILs employed, only the phosphonium-based IL THTDPCl was able to activate the p- to n-type switching. Moreover, it is revealed that for the thermoelectric parameters and performance, the SWCNT:lL ratio plays a role. In the selected systems, S-values between 61.3 μV/K (PEEK/0.75 wt % SWCNT) and -37.1 μV/K (PEEK/0.75 wt % SWCNT + 3 wt % THTDPCl) were reached. In order to shed light on the physical origins of the thermoelectric properties, the PC-based composites were studied using ultrafast laser time-resolved transient absorption spectroscopy (TAS). The TAS studies revealed that the introduction of ILs in the developed PC/CNT composites leads to the formation of biexcitons when compared to the IL-free composites. Moreover, no direct correlation between S and exciton lifetimes was found for the IL-containing composites. Instead, the exciton lifetime decreases while the conductivity seems to increase due to the availability of more free-charge carriers in the polymer matrix.

Improved High Temperature Thermoelectric Properties in Misfit Ca3Co4O9 by Thermal Annealing

Ca3Co4O9, a p-type thermoelectric material based on transition-metal oxides, has garnered significant interest due to its potential in thermoelectric applications. Its unique misfit-layered crystal structure contributes to low thermal conductivity and a high Seebeck coefficient, leading to a thermoelectric figure of merit (zT) of ≥1 at 1000 K. Conventionally, it has been believed that thermopower reaches its upper limit above 200 K. However, our thermopower measurements on polycrystalline Ca3Co4O9 samples have revealed an unexpected increase in thermopower above 380 K. In this study, we investigate the effects of high oxygen pressure annealing on Ca3Co4O9 and provide an explanation based on the mixed oxide states of cobalt and carrier hopping. Our results demonstrate that annealing induces modifications in the defect chemistry of Ca3Co4O9, leading to a decrease in electron hopping probability and the emergence of a thermal activation-like behavior in thermopower. These findings carry significant implications for the design and optimization of thermoelectric materials based on misfit cobaltates, opening new avenues for enhanced thermoelectric performance.

Neutron-irradiated effect on the thermoelectric properties of Bi2Te3-based thermoelectric leg

Thermoelectric (TE) materials working in radioisotope thermoelectric generators are irradiated by neutrons throughout its service; thus, investigating the neutron irradiation stability of TE devices is necessary. Herein, the influence of neutron irradiation with fluences of 4.56 × 1010 and 1 × 1013 n/cm2 by pulsed neutron reactor on the electrical and thermal transport properties of n-type Bi2Te2.7Se0.3 and p-type Bi0.5Sb1.5Te3 thermoelectric alloys prepared by cold-pressing and molding is investigated. After neutron irradiation, the properties of thermoelectric materials fluctuate, which is related to the material type and irradiation fluence. Different from p-type thermoelectric materials, neutron irradiation has a positive effect on n-type Bi2Te2.7Se0.3 materials. This result might be due to the increase of carrier mobility and the optimization of electrical conductivity. Afterward, the effects of p-type and n-type TE devices with different treatments on the output performance of TE devices are further discussed. The positive and negative effects caused by irradiation can cancel each other to a certain extent. For TE devices paired with p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric legs, the generated power and conversion efficiency are stable after neutron irradiation.

Colossal figure of merit and compelling HER catalytic activity of holey graphyne

Herein, we have conducted a comprehensive study to uncover the thermal transport properties and hydrogen evolution reaction catalytic activity of recently synthesized holey graphyne. Our findings disclose that holey graphyne has a direct bandgap of 1.00 eV using the HSE06 exchange–correlation functional. The absence of imaginary phonon frequencies in the phonon dispersion ensures its dynamic stability. The formation energy of holey graphyne turns out to be − 8.46 eV/atom, comparable to graphene (− 9.22 eV/atom) and h-BN (− 8.80 eV/atom). At 300 K, the Seebeck coefficient is as high as 700 μV/K at a carrier concentration of 1 × 1010 cm-2. The predicted room temperature lattice thermal conductivity (κl) of 29.3 W/mK is substantially lower than graphene (3000 W/mK) and fourfold smaller than C3N (128 W/mK). At around 335 nm thickness, the room temperature κl suppresses by 25%. The calculated p-type figure of merit (ZT) reaches a maximum of 1.50 at 300 K, higher than that of holey graphene (ZT = 1.13), γ-graphyne (ZT = 0.48), and pristine graphene (ZT = 0.55 × 10–3). It further scales up to 3.36 at 600 K. Such colossal ZT values make holey graphyne an appealing p-type thermoelectric material. Besides that, holey graphyne is a potential HER catalyst with a low overpotential of 0.20 eV, which further reduces to 0.03 eV at 2% compressive strain.

Effects of Sn and In Double-Doping on the Thermoelectric Performance of Cu3Sb1-x-ySnxInyS4 Famatinites

Famatinite (Cu3SbS4 ) is a promising p-type thermoelectric material because of its low lattice thermal conductivity and high Seebeck coefficient. In this study, famatinite powders, double-doped with Sn (a BIV group element) and In (a BIII group element) to give Cu3Sb1-x-ySnxInyS4 (0.02 ≤ x ≤ 0.12 and 0.06 ≤ y ≤ 0.10), were synthesized by mechanical alloying and then consolidated by hot pressing. Phase analysis and microstructure observations were conducted over a range of doping levels, and the charge transport parameters and thermoelectric properties were evaluated. Except for the specimen with y = 0.10, in which the secondary phase CuInS2 was found, all the specimens exhibited a tetragonal famatinite phase without secondary phases. The Sn/In double doping increased the unit cell a-axis to 0.5387–0.5389 nm and changed the c-axis to 1.0744–1.0752 nm. As the temperature increased, the electrical conductivity decreased while the Seebeck coefficient increased, which indicates that the Sn/In double-doped famatinites have degenerate semiconductor characteristics. With increasing Sn and In content, the carrier concentration increased, so that the electrical conductivity increased and the Seebeck coefficient decreased. Cu3Sb0.80Sn0.12In0.08S4 exhibited the highest power factor, 0.87 mW m-1 K-2 at 623 K, with greatly increased thermal conductivity. Cu3Sb0.86Sn0.08In0.06S4 showed the highest value for the dimensionless figure of merit, ZT = 0.53 at 623 K, with a power factor of 0.78 mW m-1 K-2 and thermal conductivity of 0.90 W m-1 K-1.

A theoretical benchmark for the electronic, optical, and thermoelectrical characteristics of bulk and monolayer BiS2

The electronic, optical, and thermoelectrical characteristics of bulk BiS2 (b-BiS2) and monolayer BiS2 (ml-BiS2) were analyzed and benchmarked using density functional theory (DFT) calculations. Both the ml-BiS2 and b-BiS2 structures display indirect bandgaps, where ml-BiS2 has a bandgap of 1.59 eV, which is slightly larger than that of b-BiS2 (1.51 eV). According to the presently revealed optical parameters, both counterparts of the BiS2 compound exhibit high dielectric properties, ideal photoconductivity, high refractivity, and efficient absorptivity, especially for convenient applications in the ultraviolet (UV) zone. Furthermore, the obtained phonon dispersions with positive frequencies suggest obvious dynamic stability behavior for both b-BiS2 and ml-BiS2. Finally, b-BiS2 with a Seebeck coefficient of 2300 μV/K and a figure of merit (ZT) of 0.99 and ml-BiS2 with a Seebeck coefficient of 2584 μV/K and ZT = 1 at room temperature (300 K) are promising novel p-type thermoelectric materials for the future energy industry and technology.

The thermo-E.M.F. of an n-type silicon: assessment of the contribution due to the presence of minority carriers

In the common thermoelectric theory, minority charge carriers are assumed to be absent in n- or p-type thermoelectric materials. This study considers their presence and evaluates the effects of that presence on the thermo-electromotive force (Thermo-E.M.F.) of a non-degenerate n-type semiconductor. The calculations are done in the case of silicon. The contribution due to the presence of the minority holes to the total Thermo-E.M.F. depends on the thermopower of minority carriers, their electrical and thermal conductivities. It also depends on their bulk and surface recombinations and depends on the majority carriers only through their thermal and electrical conductivities. In the case of silicon, that contribution remains generally very low although it can increase or decrease the total Thermo-E.M.F. depending on the concentration of the doping elements, the bulk and surface recombination rates, and the length of the sample.

Facile fabrication of Cu2O nanowire networks with large Seebeck coefficient for application in flexible thermoelectrics

The development of thermoelectrical nanowires and nanowire networks is crucial for application in self-powered electronics and flexible heat-to-power conversion devices. While Cu2O is a perspective p-type thermoelectric material, its research is mostly focused on the investigation of the properties of thin films or rigid cement composites with Cu2O powder fillers. In this work, Cu2O nanowire networks were fabricated by a simple technique and their thermoelectrical properties were investigated for the first time. Cu2O nanowire networks were obtained by annealing prefabricated CuO nanowire networks in an inert atmosphere at low pressure of 0.2 Torr. After annealing, nanowire networks showed a complete transition of CuO phase to Cu2O. Seebeck coefficient of Cu2O nanowire networks reached 2000 μV K−1. The estimated power factor of the Cu2O networks was found to be comparable with the Seebeck coefficient values of the state-of-the-art Cu2O thin films. The demonstrated in this work simple low-cost method for the fabrication of Cu2O nanowire networks illustrates the potential of this material for further applications in flexible thermoelectric devices.

Enhanced Thermoelectric Performance of Mg-Doped AgSbTe2 by Inhibiting the Formation of Ag2Te.

The existence of Ag2Te has always been an obstacle for p-type thermoelectric material AgSbTe2 to improve its thermoelectric performance. In this work, AgSb1-xMgxTe2 samples are synthesized by melting-slow-cooling and then spark plasma sintering (SPS). Through increasing the solubility of Ag2Te in the AgSbTe2 matrix by Mg doping, the formation of Ag2Te is inhibited. Density functional theory calculations confirm more valence bands are involved in electrical transport due to Mg doping. Therefore, the electrical conductivity of AgSb1-xMgxTe2 samples has been greatly improved due to the reduction of Ag2Te with n-type electrical conductivity. Moreover, the downward trend of ZT, which is caused by the structural transition of Ag2Te at about 418 K, disappears. Meanwhile, lattice defects form in the AgSb0.98Mg0.02Te2 sample, and Mg doping improves the configurational entropy change, resulting in a decrease in lattice thermal conductivity over the entire temperature range of measurement. Finally, a high ZT value of 1.31 at 523 K is achieved for the AgSb0.98Mg0.02Te2 sample. This study demonstrates that Mg doping can effectively improve AgSbTe2 thermoelectric performance by inhibiting the formation of the Ag2Te impurity phase.

All Cubic-Phase δ-TAGS Thermoelectrics Over the Entire Mid-Temperature Range.

GeTe-based pseudo-binary (GeTe)x (AgSbTe2 )100- x (TAGS-x) is recognized as a promising p-type mid-temperature thermoelectric material with outstanding thermoelectric performance; nevertheless, its intrinsic structural transition and metastable microstructure (due to Ag/Sb/Ge localization) restrict the long-time application of TAGS-x in practical thermoelectric devices. In this work, a series of non-stoichiometric (GeTe)x (Ag1- δ Sb1+ δ Te2+ δ )100- x (x= 85∼50; δ=≈0.20-0.23), referred to as δ-TAGS-x, with all cubic phase over the entire testing temperature range (300-773 K), is synthesized. Through optimization of crystal symmetry and microstructure, a state-of-the-art ZTmax of 1.86 at 673 K and average ZTavg of 1.43 at ≈323-773 K are realized in δ-TAGS-75 (δ= 0.21), which is the highest value among all reported cubic-phase GeTe-based thermoelectric systems so far. As compared with stoichiometric TAGS-x, the remarkable thermoelectric achieved in cubic δ-TAGS-x can be attributed to the alleviation of highly (electrical and thermal) resistive grain boundary Ag8 GeTe6 phase. Moreover, δ-TAGS-x exhibits much better mechanical properties than stoichiometric TAGS-x, together with the outstanding thermoelectric performance, leading to a robust single-leg thermoelectric module with ηmax of ≈10.2% and Pmax of ≈0.191W. The finding in this work indicates the great application potential of non-stoichiometric δ-TAGS-x in the field of mid-temperature waste heat harvesting.

Silver Atom Off-Centering in Diamondoid Solid Solutions Causes Crystallographic Distortion and Suppresses Lattice Thermal Conductivity.

The class I-III-VI2 diamondoid compounds with tetrahedral bonding are important semiconductors widely applied in optoelectronics. Understanding their heat transport properties and developing an effective method to predict the diamondoid solid solutions' thermal conductivity will help assess their impact as thermoelectrics. In this work, we investigated in detail the heat transport properties of CuGa1-xInxTe2 and Cu1-xAgxGaTe2 and found that in the Ag-alloyed solid solutions, the Ag atom off-centering effect results in crystallographic distortion and extra strong acoustic-optical phonon scattering and an extremely low lattice thermal conductivity. Moreover, we integrate the alloy scattering and the off-centering effect with the crystallographic distortion parameter to develop a modified Klemens model that predicts the thermal conductivity of diamondoid solid solutions. Finally, we demonstrate that Cu1-xAgxGaTe2 solid solutions are promising p-type thermoelectric materials, with a maximum ZT of 1.23 at 850 K for Cu0.58Ag0.4GaTe2.

Enhancement of electrical transport properties in CrSi2-NbSi2 composite synthesized by the AM-SPS technique

Waste heat can be harnessed into electrical energy by employing thermoelectric power generation devices. Chromium disilicides are being considered as p-type thermoelectric material which is used in thermoelectric devices for waste heat recovery applications in the mid-temperature regime owing to their low cost, stability and constitute of earth-abundant elements. In the current work, spark plasma sintering was used to develop CrSi2-NbSi2 composite materials via arc melting. The surface morphology of all the synthesized samples was examined using a field emission scanning electron microscope and the elemental mapping confirms the homogenous distribution of both the CrSi2-NbSi2 phases. The phase structure of each sample was identified using X-ray diffraction. The Seebeck coefficient and the resistivity was determined for all the samples between 300 K and 800 K. A significant power factor value of ≃ 1.44 × 10-3 W/mK2 was achieved at 423 K in an optimized composition of CrSi2/2 wt% NbSi2 material in comparison to pristine ≃ 0.92 × 10-3 W/mK2 sample. It is primarily caused by the metallic NbSi2 phase that was incorporated into the CrSi2 matrix, which increased electrical conductivity and leads to the enhancement of thermoelectric performance of CrSi2.

High thermoelectric performance of two-dimensional layered AB2Te4 (A = Sn, Pb; B = Sb, Bi) ternary compounds.

The thermoelectric properties of two-dimensional layered ternary compounds AB2Te4, in which A (Sn, Pb) and B(Sb, Bi) are group-IV and group-V cations, respectively, were investigated by using first-principles based transport theory. These septuple-atom-layer monolayers have wider band gaps with respect to their bulks, which extend their operating temperature and inhibit the bipolar carrier conduction and thermal conductivity, and more importantly, their energy bands exhibit multiple valence band convergence to a narrow energy range near the Brillouin zone center, which induces an optimal p-type power factor up to 10.94-32.11 W m-1 K-2 at room temperature. Moreover, these monolayers contain heavy atomic masses and high polarizability of some chemical bonds, leading to small group velocities of phonons and anharmonic phonon behavior that produce an intrinsic lattice thermal conductivity as low as 0.79-3.13 W m-1 K-1 at room temperature. Thus, these monolayers act as p-type thermoelectric materials with thermoelectric figure of merit of up to 2.6-5.5 for SnSb2Te4, 0.7-2.2 for PbSb2Te4, and 1.6-4.2 for PbBi2Te4 in the temperature range of 300 to 750 K, and 4.5-5.9 for SnBi2Te4 in the temperature range of 300 to 450 K.

Evolution of Thermoelectric and Oxidation Properties in Lu-Substituted Yb14MnSb11

Yb14MnSb11 is one of the state-of-the-art high-temperature p-type thermoelectric materials with reported zTs of 1.2–1.3 at 1273 K. Site substitution of Yb14MnSb11 provides a means to control carrier concentration and impacts the oxidation kinetics. Substitution of Lu3+ for Yb2+ in Yb14MnSb11 single crystals has been shown to provide faster oxidation kinetics compared with the pristine phase, and it has been speculated that this may lead to surface passivation. Polycrystalline samples of Yb14–xLuxMnSb11 were synthesized from the elements and through a route utilizing YbH2, MnSb, and Yb4Sb3 as reactive precursors. The solubility of Lu was found to be less than x = 0.5, and at that composition and above LuSb impurities are observed in the powder X-ray diffraction. Because Lu3+ is substituting for Yb2+ in a p-type system, there is an increase in both the electrical resistivity and Seebeck coefficient with Lu substitution. As Yb14MnSb11 has been predicted to be optimally doped ∼1.5 × 1021 h+ cm–3, this reduction in carrier concentration in the solid solution of Yb14–xLuxMnSb11 decreases the peak zT. Oxidation of Yb13.7Lu0.3MnSb11 as a function of temperature was studied. At low temperatures, the Lu-substituted sample may have improved oxidation resistance through forming a passivating oxide film on the surface.