#
Thermoelectric Properties of CoCrFeNiNb_{x} Eutectic High Entropy Alloys

^{1}

^{2}

^{*}

## Abstract

**:**

_{0.45}eutectic high entropy alloy (EHEA) with ultrafine-lamellar microstructure shows outstanding thermal stability. The EHEA offers opportunities for the development of thermoelectric materials. In this paper, the thermoelectric properties of a CoCrFeNiNb

_{x}(x = 0, 0.25, and 0.45) EHEA system were investigated. The results indicated that the electrical conductivity decreased with a rise in Nb content in the CoCrFeNiNb

_{x}alloys, which resulted from the increased eutectic structure and phase interface. Moreover, the thermal conductivity increased with increased Nb content at low temperature (T ≤ 473 K), while thermal conductivity decreased at high temperature (T > 573 K). The CoCrFeNiNb

_{0.45}full eutectic high entropy alloy exhibited the lowest thermal conductivity and higher thermoelectric figure of merit (ZT) at a high temperature (T > 573 K), which shows great promise for the thermoelectric application at high temperature.

## 1. Introduction

^{2}σT)/k, where α is the Seebeck coefficient, σ is the electrical conductivity, k is the thermal conductivity, and T is the absolute temperature in Kelvin [5,6]. To maximize the ZT of a thermoelectric material, high α, σ and low k are required. However, it is quite difficult to achieve the above conditions simultaneously because of the competition with three parameters. Up to now, nanostructured materials changing these parameters independently lead to increase the ZT due to quantum confinement and nanostructure effects [7,8,9]. Although reducing the size of materials in nano-scale has been demonstrated to be an effective method to improve the thermoelectric performance, several disadvantages also exist. Firstly, many of these materials are not practical for large-scale application. Secondly, the nanostructure materials have low thermal stability, such as significant grain growth during thermal consolidation, weakening the effect of nanostructures. Therefore, for practical thermoelectric application, developing new thermoelectric materials with scalable, low cost, high thermoelectric performance and high thermal stability for extended periods of time is required.

_{2.1}EHEA showed good liquidity, castability and good mechanical properties [25,26,27]. Recently, the EHEAs have been extensive studied for their eutectic composition and mechanical properties [28,29,30,31,32,33,34,35,36,37]. However, little research has focused on the physical properties of EHEAs (electrical, magnetic properties, thermal conductivity, etc.).

_{0.45}EHEA [38]. For the ultrafine eutectic structure, phonons are more strongly scattered by the interfaces, resulting in an increase in ZT. In addition, the in-situ synthetic EHEAs also have several beneficial features relative to the conventional nanostructure thermoelectric materials, such as high thermodynamic stability, low-cost method, low-energy phase boundaries and high symmetry crystal structures. Hence, the EHEAs may offer opportunities for the development of thermoelectric materials. The microstructure of the CoCrFeNiNb

_{x}(x = 0, 0.25, and 0.45) alloy system changing from a simple FCC solid solution structure (x = 0) to hypoeutectic (x = 0.25), then to a full eutectic structure (x = 0.45) has been reported in our previous works [39]. So, in this paper, the thermoelectric properties of CoCrFeNiNb

_{x}(x = 0, 0.25, and 0.45) EHEAs were measured to investigate the effect of microstructure and composition on the thermoelectric properties.

## 2. Experimental

_{x}(x = 0, 0.25, and 0.45 denoted as Nb0, Nb0.25, and Nb0.45) eutectic high entropy alloy button ingots were prepared by co-melting elemental pure (higher than 99.95 wt. %) Co, Cr, Fe, Ni, Nb in an arc melting furnace under Ar-atmosphere. In order to obtain chemical homogeneity, the alloy ingots were melted at least five times. The microstructure was observed by scanning electron microscopy (SEM, Zeiss supra 55, Oberkochen, Germany) and transmission electron microscopy (TEM, JEOL-2100, JEOL, Japan). The specific electrical resistivity (1/σ) and Seebeck coefficients (α) were measured by Namicro-3 from Wuhan Joule Yacht Science Technology Co., Ltd. with a sample dimension of 2.5 mm × 2.5 mm × 12 mm. Measurements were performed from room temperature to 800 °C (28 °C, 100 °C, 200 °C, 300 °C, 400 °C, 500 °C, 600 °C, 700 °C and 800 °C) under vacuum condition. The disk samples with a dimension of Φ12.7 mm × 2.5 mm were cut from alloy ingots and then grinded and polished to obtain a smooth surface before the thermal conductivity test. Thermal conductivity (k) was evaluated using NETZSCH LFA 427 (Ruixuan Electronic Technology, Shanghai, China) by measuring thermal diffusivity (D) and using the formula k = D·ρ·C

_{p}. The geometrical density ρ was directly measured and heat capacity C

_{p}was measured via STA449F1 from NETZSCH (Shanghai, China). The thermal conductivity of the alloys was measured between room temperature and 550 °C, and the interval was kept at 100 °C.

## 3. Results and Discussion

_{x}ingots were investigated as shown in Figure 1a–f [38,39]. Results indicated the microstructure changed from simple FCC solid structure (x = 0) to hypoeutectic with the primary FCC phase (x = 0.25) then to eutectic and finally (x = 0.45). For the bulk CoCrFeNiNb

_{0.45}eutectic alloy, regular cellular eutectic containing ultrafine (nearly nanometer-sized)/regular lamellar eutectic structure can be observed. The highly uniform nanometer-sized material is rarely obtained using conventional casting. This provided an opportunity for the industrial application of the nanostructured material.

_{x}alloys in this paper. The temperature-dependent electrical conductivity (σ) is shown in Figure 2. The specific electrical conductivity values are listed in Table 1. From the electrical conductivity data, we observed that the CoCrFeNi alloy without Nb element possesses higher electrical conductivity (σ) values than that of CoCrFeNiNb

_{x}(x = 0.25, 0.45) alloy with different Nb content at all the test temperature. In addition, the electrical conductivity of the CoCrFeNiNb

_{x}(x = 0, 0.25, and 0.45) alloys decreased with an increase in the Nb element (see Figure 2). This variation reflects the effect of microstructure morphology on the electrical property. The increase in the Nb element resulted in the increase in the volume fraction of eutectic structure; correspondingly, the amounts of the two-phase eutectic interface increased. The F-S theory was proposed by Fuchs and Sondheimer [41], which revealed the effect of the external surfaces on the electrical conductivity of the thin metal films. According to the F-S theory and the two-fluid model, the moving electrons will be scattered on the surface and at grain boundaries, which will lead to a decrease in the effective electric charge density and a decrease in electrical conductivity. In addition, the Nb element with a larger atomic radius relative to the other composition elements (the radius of Nb is 1.47 Å, the radii of the Co, Cr, Fe, and Ni elements are 1.25, 1.28, 1.26, 1.24 Å) was added into CoCrFeNi alloy causing large lattice strain. This led to a decreased carrier mobility and thus decreased electrical conductivity. With increasing temperature, the electrical conductivity decreased linearly in all the CoCrFeNiNb

_{x}alloys. The trend was consistent with the electrical resistivity dependence of the temperature in metals. The dependence of electrical resistivity on the temperature [42] is often expressed as

_{s}is the electrical resistivity at temperature T, ρ

_{0}is the electrical resistivity at room temperature T

_{0}, and A is the temperature coefficient of resistivity.

_{x}EHEAs was significantly higher than that of conventional binary Al-Ni eutectic [42] and some HEAs, such as the Al

_{x}CoCrFeNi (0 ≤ x ≤ 2) [43], Al

_{x}CrFeNi (x = 1.2, 1.3) [44].

_{B}is the Boltzmann constant, h is Planck constant, e is the carrier charge, n is the carrier concentration and m* is the density-of-states effective mass of the carrier. Thus, the raised Seebeck coefficient from 300 °C to 800 °C (see Figure 3) may come from the increase in the total number of charge carriers. From RT to 300 °C, the Seebeck coefficient lost its temperature dependency, which might be attributed to the charge carriers becoming partially localized in this temperature range.

_{x}alloys are displayed in Figure 4. It can be found that at a low temperature (T ≤ 473 K) the thermal conductivity increases with increased Nb content. Then, at a high temperature (T > 573 K), the increased Nb content resulted in the decrease in thermal conductivity, which is in agreement with the prediction of Mingo [46]. As we know, both electrons (K

_{e}) and phonons (k

_{p}) contribute to the thermal conductivity, in which phonons usually have the majority contribution. Furthermore, the existent of interfaces and boundaries to scatter phonons is more effective than electrons. Thus, the enhanced interface and boundary phonon scattering contributed to the reduction in thermal conductivity. Moreover, the CoCrFeNiNb

_{x}(x = 0.25 and 0.45) alloys exhibited a eutectic structure in situ formation, which is believed to have relatively low lattice thermal conductivity in this alloy system. In particular, the CoCrFeNiNb

_{0.45}alloy with full eutectic microstructure exhibited the lowest thermal conductivity at a high temperature (T > 573 K). The ultrafine CoCrFeNiNb

_{0.45}EHEA shows outstanding microstructure thermal stability up to 1100 °C, which gives the alloy low thermal conductivity. Compared to the thermal conductivities of these HEAs and conventional metals, it can be found that the thermal conductivity of CoCrFeNiNb

_{x}alloys is lower than those of most pure metals, but is higher than those of conventional metals such as 304 stainless steel or Ni-based super-alloys [47].

_{x}alloys. In addition, the CoCrFeNiNb

_{0.45}full EHEA has the highest ZT at high temperature (T > 573 K), which resulted from the lower thermal conductivity of the CoCrFeNiNb

_{0.45}alloy. From Figure 2, it can be found the electrical conductivity of the single phase CoCrFeNi HEAs was obviously higher than that of the CoCrFeNiNb

_{0.45}EHEA. The above results showed the EHEA with bimodal structure may show a great promise for thermoelectric applications.

## 4. Conclusions

_{x}(x = 0, 0.25, and 0.45) alloys, the following conclusions can be drawn:

- (1)
- With a rise in Nb content in the CoCrFeNiNb
_{x}alloys, the amounts of eutectic structure and phase interface increased, which decreased the electrical conductivity. - (2)
- The thermal conductivity of the CoCrFeNiNb
_{x}alloys increases with the increase in temperature. The CoCrFeNiNb_{0.45}full eutectic alloy exhibited the lowest thermal conductivity at a high temperature (T > 573 K). - (3)
- The CoCrFeNiNb
_{0.45}full eutectic high entropy alloy has the highest ZT at high temperature (T > 573 K), which resulted from the lower thermal conductivity of the CoCrFeNiNb_{0.45}alloy.

## Author Contributions

## Funding

## Conflicts of Interest

## References

- Chen, Z.; Ge, B.; Li, W.; Lin, S.; Shen, J.; Chang, Y.; Hanus, R.; Snyder, G.J.; Pei, Y. Vacancy-induced dislocations within grains for high-performance PbSe thermoelectrics. Nat. Commun.
**2017**, 8, 13828. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Alam, H.; Ramakrishna, S. A review on the enhancement of figure of merit from bulk to nano-thermoelectric materials. Nano Energy
**2013**, 2, 190–212. [Google Scholar] [CrossRef] - He, J.; Tritt, T.M. Advances in thermoelectric materials research: Looking back and moving forward. Science
**2017**, 357, eaak9997. [Google Scholar] [CrossRef] [PubMed] [Green Version] - Wolf, M.; Hinterding, R.; Feldhoff, A. High power factor vs. high zT—A Review of thermoelectric materials for high-temperature application. Entropy
**2019**, 21, 1058. [Google Scholar] [CrossRef] [Green Version] - Stoetzel, J.; Schneider, T.; Mueller, M.M.; Kleebe, H.-J.; Wiggers, H.; Schierning, G.; Schmechel, R. Microstructure and thermoelectric properties of Si-WSi2 nanocomposites. Acta Mater.
**2017**, 125, 321–326. [Google Scholar] [CrossRef] - Zhang, J.; Song, L.; Pedersen, S.H.; Yin, H.; Hung, L.T.; Iversen, B.B. Discovery of high-performance low-cost n-type Mg
_{3}Sb_{2}-based thermoelectric materials with multi-valley conduction bands. Nat. Commun.**2017**, 8, 13901. [Google Scholar] [CrossRef] [Green Version] - Liu, Z.; Gao, W.; Meng, X.; Li, X.; Mao, J.; Wang, Y.; Shuai, J.; Cai, W.; Ren, Z.; Sui, J. Mechanical properties of nanostructured thermoelectric materials α-MgAgSb. Scr. Mater.
**2017**, 127, 72–75. [Google Scholar] [CrossRef] [Green Version] - Chen, Z.G.; Han, G.; Yang, L.; Cheng, L.; Zou, J. Nanostructured thermoelectric materials: Current research and future challenge. Prog. Nat. Sci. Mater.
**2012**, 22, 535–549. [Google Scholar] [CrossRef] [Green Version] - Liang, L.; Chen, G.; Guo, C.Y. Polypyrrole nanostructures and their thermoelectric performance. Mater. Chem. Front.
**2017**, 1, 380–386. [Google Scholar] [CrossRef] - Yeh, J.W.; Chen, S.K.; Lin, S.J.; Gan, J.Y.; Chin, T.S.; Shun, T.T.; Tsau, C.H.; Chang, S.Y. Nanostructured high-entropy alloys with multiple principal elements: Novel alloy design concepts and outcomes. Adv. Eng. Mater.
**2004**, 6, 299–303. [Google Scholar] [CrossRef] - Cantor, B.; Chang, I.T.H.; Knight, P.; Vincent, A.J.B. Microstructural development in equiatomic multicomponent alloys. Mater. Sci. Eng. A
**2004**, 375–377, 213–218. [Google Scholar] [CrossRef] - Zhang, Y.; Zuo, T.T.; Tang, Z.; Gao, M.C.; Dahmen, K.A.; Liaw, P.K.; Lu, Z.P. Microstructures and properties of high-entropy alloys. Prog. Mater. Sci.
**2014**, 61, 1–93. [Google Scholar] [CrossRef] - Gao, M.C.; Yeh, J.W.; Liaw, P.K.; Zhang, Y. High Entropy Alloys Fundamentals and Applications; Springer International Publishing: Cham, Switzerland, 2016. [Google Scholar]
- Yeh, J.W. Alloy Design strategies and future trends in high-entropy alloys. JOM
**2013**, 65, 1759–1771. [Google Scholar] [CrossRef] - Beke, D.L.; Erdélyi, G. On the diffusion in high-entropy alloys. Mater. Lett.
**2016**, 164, 111–113. [Google Scholar] [CrossRef] - Liu, W.H.; Wu, Y.; He, J.Y.; Nieh, T.G.; Lu, Z.P. Grain growth and the Hall–Petch relationship in a high-entropy FeCrNiCoMn alloy. Scr. Mater.
**2013**, 68, 526–529. [Google Scholar] [CrossRef] - Li, Z.; Pradeep, K.G.; Deng, Y.; Raabe, D.; Tasan, C.C. Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off. Nature
**2016**, 534, 227–230. [Google Scholar] [CrossRef] - Zhang, Y.; Yang, X.; Liaw, P.K. Alloy design and properties optimization of high-entropy alloys. JOM
**2012**, 64, 830–838. [Google Scholar] [CrossRef] - Gludovatz, B.; Hohenwarter, A.; Catoor, D.; Chang, E.H.; George, E.P.; Ritchie, R.O. A fracture-resistant high-entropy alloy for cryogenic applications. Science
**2014**, 345, 1153–1158. [Google Scholar] [CrossRef] [Green Version] - Stepanov, N.D.; Yurchenko, N.Y.; Sokolovsky, V.S.; Tikhonovsky, M.A.; Salishchev, G.A. An AlNbTiVZr
_{0.5}high-entropy alloy combining high specific strength and good ductility. Mater. Lett.**2015**, 161, 136–139. [Google Scholar] [CrossRef] - Zuo, T.T.; Gao, M.C.; Ouyang, L.Z.; Yang, X.; Cheng, Y.Q.; Feng, R.; Chen, S.Y.; Liaw, P.K.; Hawk, J.A.; Zhang, Y. Tailoring magnetic behavior of CoFeMnNiX (X = Al, Cr, Ga, and Sn) high entropy alloys by metal doping. Acta Mater.
**2017**, 130, 10–18. [Google Scholar] [CrossRef] [Green Version] - Lu, C.; Yang, T.; Jin, K.; Gao, N.; Xiu, P.; Zhang, Y.; Gao, F.; Bei, H.; Weber, W.J.; Sun, K.; et al. Radiation-induced segregation on defect clusters in single-phase concentrated solid-solution alloys. Acta Mater.
**2017**, 127, 98–107. [Google Scholar] [CrossRef] - Shi, Y.; Yang, B.; Xie, X.; Brechtl, J.; Dahmen, K.A.; Liaw, P.K. Corrosion of Al
_{x}CoCrFeNi high-entropy alloys: Al-content and potential scan-rate dependent pitting behavior. Corros. Sci.**2017**, 119, 33–45. [Google Scholar] [CrossRef] - Lu, Y.; Dong, Y.; Guo, S.; Jiang, L.; Kang, H.; Wang, T.; Wen, B.; Wang, Z.; Jie, J.; Cao, Z.; et al. A promising new class of high-temperature alloys: Eutectic high-entropy alloys. Sci. Rep.
**2014**, 4, 6200. [Google Scholar] [CrossRef] [PubMed] - Lu, Y.; Gao, X.; Jiang, L.; Chen, Z.; Wang, T.; Jie, J.; Kang, H.; Zhang, Y.; Guo, S.; Ruan, H.; et al. Directly cast bulk eutectic and near-eutectic high entropy alloys with balanced strength and ductility in a wide temperature range. Acta Mater.
**2017**, 124, 143–150. [Google Scholar] [CrossRef] [Green Version] - Wani, I.S.; Bhattacharjee, T.; Sheikh, S.; Lu, Y.P.; Chatterjee, S.; Bhattacharjee, P.P.; Guo, S.; Tsuji, N. Ultrafine-grained AlCoCrFeNi
_{2.1}eutectic high-entropy alloy. Mater. Res. Lett.**2016**, 4, 174–179. [Google Scholar] [CrossRef] [Green Version] - Wani, I.S.; Bhattacharjee, T.; Sheikh, S.; Clark, I.T.; Park, M.H.; Okawa, T.; Guo, S.; Bhattacharjee, P.P.; Tsuji, N. Cold-rolling and recrystallization textures of a nano-lamellar AlCoCrFeNi
_{2.1}eutectic high entropy alloy. Intermetallics**2017**, 84, 42–51. [Google Scholar] [CrossRef] - Lu, Y.; Dong, Y.; Jiang, H.; Wang, Z.; Cao, Z.; Guo, S.; Wang, T.; Li, T.; Liaw, P.K. Promising properties and future trend of eutectic high entropy alloys. Scr. Mater.
**2020**, 187, 202–209. [Google Scholar] [CrossRef] - Wu, Q.; Wang, Z.; Zheng, T.; Chen, D.; Yang, Z.; Li, J.; Kai, J.J.; Wang, J. A casting eutectic high entropy alloy with superior strength-ductility combination. Mater. Lett.
**2019**, 253, 268–271. [Google Scholar] [CrossRef] - Dong, Y.; Yao, Z.; Huang, X.; Du, F.; Li, C.; Chen, A.; Wu, F.; Cheng, Y.; Zhang, Z. Microstructure and mechanical properties of AlCo
_{x}CrFeNi_{3-x}eutectic high-entropy-alloy system. J. Alloy. Compd.**2020**, 823, 153886. [Google Scholar] [CrossRef] - Wu, M.; Munroe, P.R.; Baker, I. Martensitic phase transformation in a f.c.c./B2 FeNiMnAl alloy. J. Mater. Sci.
**2016**, 51, 7831–7842. [Google Scholar] [CrossRef] - Samal, S.; Rahul, M.R.; Kottada, R.S.; Phanikumar, G. Hot deformation behaviour and processing map of Co-Cu-Fe-Ni-Ti eutectic high entropy alloy. Mater. Sci. Eng. A
**2016**, 664, 227–235. [Google Scholar] [CrossRef] - Rogal, Ł.; Morgiel, J.; Świątek, Z.; Czerwiński, F. Microstructure and mechanical properties of the new Nb
_{25}Sc_{25}Ti_{25}Zr_{25}eutectic high entropy alloy. Mater. Sci. Eng. A**2016**, 651, 590–597. [Google Scholar] [CrossRef] - He, F.; Wang, Z.J.; Cheng, P.; Wang, Q.; Li, J.J.; Dang, Y.Y.; Wang, J.C.; Liu, C.T. Designing eutectic high entropy alloys of CoCrFeNiNb
_{x}. J. Alloy. Compd.**2016**, 656, 284–289. [Google Scholar] [CrossRef] - Guo, S.; Ng, C.; Liu, C.T. Anomalous solidification microstructures in Co-free Al
_{x}CrCuFeNi_{2}high-entropy alloys. J. Alloy. Compd.**2013**, 557, 77–81. [Google Scholar] [CrossRef] - Tan, Y.M.; Li, J.S.; Wang, J.; Kou, H.C. Seaweed eutectic-dendritic solidification pattern in a CoCrFeNiMnPd eutectic high-entropy alloy. Intermetallics
**2017**, 85, 74–79. [Google Scholar] [CrossRef] - Jin, X.; Zhou, Y.; Zhang, L.; Du, X.Y.; Li, B.S. A novel Fe
_{20}Co_{20}Ni_{41}Al_{19}eutectic high entropy alloy with excellent tensile properties. Mater. Lett.**2018**, 216, 144–146. [Google Scholar] [CrossRef] - Jiang, H.; Qiao, D.X.; Lu, Y.P.; Ren, Z.; Cao, Z.Q.; Wang, T.M.; Li, T.J. Direct solidification of bulk ultrafine-microstructure eutectic high-entropy alloys with outstanding thermal stability. Scr. Mater.
**2019**, 165, 145–149. [Google Scholar] [CrossRef] - Jiang, H.; Jiang, L.; Qiao, D.X.; Lu, Y.P.; Wang, T.M.; Cao, Z.Q.; Li, T.J. Effect of Niobium on Microstructure and Properties of the CoCrFeNb
_{x}Ni High Entropy Alloys. J. Mater. Sci. Technol.**2016**, 33, 712–717. [Google Scholar] [CrossRef] - Bento, J.L.; Brown, E.; Woltornist, S.J.; Adamson, D.H. Thermal and electrical properties of nanocomposites based on self-assembled pristine graphene. Adv. Funct. Mater.
**2017**, 27, 1604277. [Google Scholar] [CrossRef] - Sondheimer, E.H. Mean free path of electrons in metals. Adv. Phys.
**1952**, 1, 1–42. [Google Scholar] [CrossRef] - Kaya, H.; Böyük, U.; Çadırlı, E.; Maraşlı, N. Measurements of the microhardness, electrical and thermal properties of the Al–Ni eutectic alloy. Mater. Des.
**2012**, 34, 707–712. [Google Scholar] [CrossRef] - Chou, H.P.; Chang, Y.S.; Chen, S.K.; Yeh, J.W. Microstructure, thermophysical and electrical properties in Al
_{x}CoCrFeNi (0 ≤ x ≤ 2) high-entropy alloys. Mater. Sci. Eng. B**2009**, 163, 184–189. [Google Scholar] [CrossRef] - Sui, Y.; Gao, S.; Chen, X.; Qi, J.; Yang, F.; Wei, F.; He, Y.; Meng, Q.K.; Sun, Z. Microstructures and electrothermal properties of Al
_{x}CrFeNi multi-component alloys. Vacuum**2017**, 144, 80–85. [Google Scholar] [CrossRef] - Cassinelli, M.; Muller, S.; Voss, K.O.; Trautmann, C.; Volklein, F.; Gooth, J.; Nielsch, K.; Toimil-Molares, M.E. Influence of surface states and size effects on the Seebeck coefficient and electrical resistance of Bi
_{1-x}Sb_{x}nanowire arrays. Nanoscale**2017**, 9, 3169–3179. [Google Scholar] [CrossRef] [PubMed] - Mingo, N.; Hauser, D.; Kobayashi, N.P.; Plissonnier, M.; Shakouri, A. Nanoparticlein alloy approach to efficient thermoelectrics: Silicides in sige. Nano Lett.
**2009**, 9, 711–715. [Google Scholar] [CrossRef] - Shackelford, J.F.; Alexander, W. (Eds.) CRC Materials Science and Engineering Handbook, 3rd ed.; CRC Press: Boca Raton, FL, USA, 2000. [Google Scholar]
- Lide, D.R. (Ed.) CRC Handbook of Chemistry and Physics, 84th ed.; CRC Press: Boca Raton, FL, USA, 2003. [Google Scholar]

**Table 1.**The specific electric resistance and electrical conductivity values of the CoCrFeNiNb

_{x}(x = 0, 0.25, and 0.45) alloys.

Alloys | Temperature | 28 °C | 100 °C | 200 °C | 300 °C | 400 °C | 500 °C | 600 °C | 700 °C | 800 °C |
---|---|---|---|---|---|---|---|---|---|---|

Nb0 | Electric resistance (μΩ·m) | 0.7776 | 0.8330 | 0.8665 | 0.8996 | 0.9289 | 0.9605 | 0.9840 | 1.0026 | 1.0205 |

Electrical conductively (mS·m^{−1}) | 1.286 | 1.2004 | 1.1541 | 1.1116 | 1.0766 | 1.0411 | 1.0162 | 0.9974 | 0.9799 | |

Nb0.25 | Electric resistance (μΩ·m) | 1.0894 | 1.1629 | 1.2056 | 1.2399 | 1.2719 | 1.2996 | 1.3202 | 1.3354 | 1.3430 |

Electrical conductively (mS·m^{−1}) | 0.918 | 0.8599 | 0.8295 | 0.8065 | 0.7862 | 0.7695 | 0.7575 | 0.7488 | 0.7446 | |

Nb0.45 | Electric resistance (μΩ·m) | 1.1417 | 1.1810 | 1.2173 | 1.2527 | 1.2811 | 1.3082 | 1.3313 | 1.3448 | 1.3540 |

Electrical conductively (mS·m^{−1}) | 0.8759 | 0.8467 | 0.8215 | 0.7982 | 0.7806 | 0.7644 | 0.75112 | 0.7436 | 0.7385 |

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).

## Share and Cite

**MDPI and ACS Style**

Han, K.; Jiang, H.; Huang, T.; Wei, M.
Thermoelectric Properties of CoCrFeNiNb_{x} Eutectic High Entropy Alloys. *Crystals* **2020**, *10*, 762.
https://doi.org/10.3390/cryst10090762

**AMA Style**

Han K, Jiang H, Huang T, Wei M.
Thermoelectric Properties of CoCrFeNiNb_{x} Eutectic High Entropy Alloys. *Crystals*. 2020; 10(9):762.
https://doi.org/10.3390/cryst10090762

**Chicago/Turabian Style**

Han, Kaiming, Hui Jiang, Tiandang Huang, and Mingyu Wei.
2020. "Thermoelectric Properties of CoCrFeNiNb_{x} Eutectic High Entropy Alloys" *Crystals* 10, no. 9: 762.
https://doi.org/10.3390/cryst10090762