1 High -performance non -Fermi -liquid metallic thermoelectric materials

2025-04-28 0 0 1.09MB 19 页 10玖币

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High-performance non-Fermi-liquid metallic thermoelectric

materials

Zirui Dong1,7, Yubo Zhang2,3,7, Jun Luo1,4*, Ying Jiang4, Zhiyang Yu5, Nan Zhao3, Liusuo Wu3,

Yurong Ruan2, Fang Zhang2, Kai Guo6, Jiye Zhang1, Wenqing Zhang2,3*

1 School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China

2 Department of Materials Science and Engineering, Department of Physics, and Shenzhen Institute

for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen

518055, China

3 Shenzhen Municipal Key-Lab for Advanced Quantum Materials and Devices, and Guangdong

Provincial Key Lab for Computational Science and Materials Design, Southern University of

Science and Technology, Shenzhen 518055, China

4 Materials Genome Institute, Shanghai University, Shanghai 200444, China

5 State Key Laboratory of Photocatalysis on Energy and Environment, College of Chemistry,

Fuzhou University, Fuzhou 350002, China

6 School of Physics and Materials Science, Guangzhou University, Guangzhou 510006, China

7 These authors contributed equally: Zirui Dong, Yubo Zhang.

* Correspondence to: junluo@shu.edu.cn (J.L.); zhangwq@sustech.edu.cn (W.Z.)

Abstract

Searching for high-performance thermoelectric (TE) materials in the paradigm

of narrow-bandgap semiconductors has lasted for nearly 70 years and is obviously

hampered by a bottleneck of research now1. Here we report on the discovery of a

few metallic compounds, TiFexCu2x-1Sb (x = 0.70, 0,75, 0.80) and TiFe1.33Sb,

showing the thermopower exceeding many TE semiconductors and the

dimensionless figure of merits zTs comparable with the state-of-the-art TE

materials. A quasi-linear temperature (T) dependence of electrical resistivity in 2

K - 700 K and the logarithmic T-dependent electronic specific heat at low

temperature are also observed to coexist with the high thermopower, highlighting

the strong intercoupling of the non-Fermi-liquid (NFL) quantum critical

behavior2 of electrons with TE transports. Electronic structure analysis reveals the

existence of fluctuating Fe-eg-related local magnetic moments, Fe-Fe

antiferromagnetic (AFM) interaction at the nearest 4c-4d sites, and two-fold

degenerate eg orbitals antiferromagnetically coupled with the dual-type itinerant

electrons close to the Fermi level, all of which infer to a competition between the

AFM ordering and Kondo-like spin compensation as well as a parallel two-

channel Kondo effect. These effects are both strongly meditated by the structural

disorder due to the random filling of Fe/Cu at the equivalent 4c/4d sites of the

Heusler crystal lattice. The temperature dependence of magnetic susceptibility

deviates from ideal antiferromagnetism but can be fitted well by 𝒙(𝑻) =

𝟏 (𝜽 + 𝑩𝑻𝜶)

⁄ , seemingly being consistent with the quantum critical scenario of

strong local correlation as discussed before3-5. Our work not only breaks the

dilemma that the promising TE materials should be heavily-doped semiconductors,

but also demonstrates the correlation among high TE performance, NFL quantum

criticality, and magnetic fluctuation, which opens up new directions for future

research.

TE materials have been researched and developed for 200 years since the Seebeck

effect was discovered in 1821. Due to the promising applications of TE materials in

waste heat power generation and solid-state refrigeration, persistent efforts have been

made to improve TE performance. Metals were studied as TE materials firstly, but they

are no longer considered as good TE materials because of their small Seebeck

coefficients and low zT values (zT = S2σT/κ, where S, σ, T, and κ are the Seebeck

coefficient or thermopower, electrical conductivity, absolute temperature, and total

thermal conductivity, respectively). Instead, the best TE materials at present, such as

Bi2Te36, PbTe7, GeTe8, and CoSb39, are all heavily-doped narrow-bandgap

semiconductors. Thus, the currently common consensus in the TE field is that the first-

rank TE material should be a heavily-doped narrow-bandgap semiconductor10, which

can achieve the optimal power factor S2σ by balancing the Seebeck coefficient and

electrical conductivity11. As a result, an optimized zT, which determines the TE

conversion efficiency, is realized.

After about 70 years of development, the only commercialized TE material is the

Bi2Te3-based material with a peak zT around the unity. In addition, reliably reproducible

zT is around 2.0, the reported zT values above 2.0 are often in debate, and all belong to

heavily-doped narrow-bandgap semiconductors1,12,13. It seems desperately needed to

break through the limitation of narrow-bandgap semiconductors for discovering novel

TE materials. Many attempts have been made to explore non-semiconductor TE

materials. High spin entropy was once believed to enhance the TE performance of a

few lamellar cobalt oxides14-16. For instance, NaxCo2O4 with Co3+/Co4+-determined spin

entropy achieves Seebeck coefficients about 100 and 200 μV K-1 at 300 K and 800 K,

repectively17,18. Up to now, the maximum zT value of this type of oxide approaches

~1.0 at 800 K after a long-time endeavor19, halted in thermodynamics by the spin

entropy limit from d-band degeneracy.

Over the years, a few rare-earth 4f-electron-based heavy-fermion systems were found

to show metallic electrical conductivities and relatively large Seebeck coefficients20 at

extremely low temperatures. There also exist a few exceptions to the recognized heavy-

fermions as YbAl321 and CePd322, showing thermopower as high as ~100 μV K-1 at

room temperature. Arguably, this was also considered as hybridizing f electrons with

conduction band, resulting in a resonant peak near the Fermi surface23,24 as in normal

materials. The peak zT values of CePt322 and YbAl321 reach about 0.2 and 0.3 at 300 K,

respectively. Nevertheless, the optimal Seebeck coefficients for both systems reach

only < 110 V K-1 and impede further enhancement of their TE performance. Very

recently, the spin fluctuation was reported to enhance the thermopower of weak

itinerant ferromagnetic alloys Fe2V0.9Cr0.1Al0.9Si0.1 and Fe2.2V0.8Al0.6Si0.425 around the

Curie temperature TC. A broad shoulder-like hump on the S(T) ~ T curve was observed

around TC, leading to only a 15% to 20% enhancement of the Seebeck coefficient at TC.

The well-known NFL superconducting oxides, such as YBa2Cu4O826 and La2-xSrCuO427,

also show certain intriguing TE behavior, but these oxides always have negligible zT

values, several orders of magnitude lower than the state-of-the-art TE semiconductors.

Conceptually, there is no substantial breakthrough in the search for non-

semiconductor TE materials. In this work, we find that a few Heusler-like materials,

TiFexCu2x-1Sb (x = 0.70, 0,75, 0.80) and TiFe1.33Sb with excess Fe/Cu occupying the

vacant sites of the half-Heusler lattice, show peculiar NFL metallic transport together

with excellent TE performance. A high power factor of 20.8 μWcm-1K-2 and a zT value

of 0.75 are achieved in TiFe0.7Cu0.4Sb at 973 K, and the other systems also show zTs

higher than 0.3, all comparable with the best half-Heusler TE semiconductors.

Unconventional metallic transport properties

Figure 1 plots the resistivity ρ(T) of TiFexCu2x-1Sb and TiFe1.33Sb. They all show

quasi-linear dependence in the range from near-zero temperature up to 500 K,

indicating that both materials are unconventional metals. Another typical characteristic

of metallicity is the vanishing small Seebeck coefficients, S(T), when approaching 0 K

(the inset of Fig. 1). The Seebeck coefficients of the TiFexCu2x-1Sb and TiFe1.33Sb

gradually increase and become comparable to those of heavily-doped narrow-bandgap

semiconductors at 300 K and higher. Moreover, the quasi-linear- or linear-T dependence

of ρ(T) in the above materials is valid in a wide temperature range (0 – 500 K in Fig. 1;

see also Supplementary Fig. 1a for a wider range of 0 – 973 K) while stably keeping

the thermopower as high as approaching 200 V K-1. By fitting to the low-temperature

resistivity with the Bloch–Grüneisen model28 (Supplementary Information section 1

and Supplementary Fig. 2 and Table 1), the parameter of Debye-temperature term is

estimated to be as low as ~40 K, much lower than the phonon-mediated Debye

temperature of 389 K estimated from the measured sound velocity (Supplementary

Information section 2 and Supplementary Table 2). X-ray photoemission spectroscopy

(XPS) experiments reveal that the Fe element in both TiFe0.7Cu0.4Sb and TiFe1.33Sb has

a valence of zero, and their Fe-2p XPS spectra are almost identical to the metallic Fe,

FeSe and FeTe but are obviously different from FeO and Fe2O3 (Supplementary Fig. 3).

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摘要：

1High-performancenon-Fermi-liquidmetallicthermoelectricmaterialsZiruiDong1,7,YuboZhang2,3,7,JunLuo1,4*,YingJiang4,ZhiyangYu5,NanZhao3,LiusuoWu3,YurongRuan2,FangZhang2,KaiGuo6,JiyeZhang1,WenqingZhang2,3*1SchoolofMaterialsScienceandEngineering,ShanghaiUniversity,Shanghai200444,China2DepartmentofMateri...

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