N-type NbFeSb-based half-Heusler thermoelectric material, and preparation method and application thereof

Abstract

The invention provides an N-type NbFeSb-based half-Heusler thermoelectric material as well as a preparation method and application thereof, the general formula of the thermoelectric material is Nb1-XCrXFe0. 94Co0. 06Sb, where 0 lt, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, and x is less than or equal to 0.3. The preparation method comprises the following steps: weighing the materials according to the general formula, putting the materials into a magnetic suspension smelting furnace for smelting, putting a cast ingot obtained after smelting into a planetary ball mill for ball milling, then carrying out suction filtration and drying to obtain powder, and sintering the powder by adopting spark plasma sintering to obtain the N-type NbFeSb-based half-Heusler thermoelectric material. According to the N-type NbFeSb-based half-Heusler thermoelectric material, the Cr element is doped, so that fluctuation of a stress field and a mass field is caused, phonon scattering is enhanced, the lattice thermal conductivity is reduced, and the thermoelectric performance is improved.

Description

Technical Field

[0001] The present invention relates to thermoelectric material technology, and in particular to an N-type NbFeSb-based half-Heusler thermoelectric material, a preparation method and application thereof. Background Art

[0002] As the global demand for renewable energy and energy conversion efficiency increases, thermoelectric materials, as a functional material that can achieve direct conversion of thermal energy into electrical energy, have received widespread attention. Thermoelectric materials can play an important role in waste heat recovery, waste heat power generation, and refrigeration through the Seebeck effect and Peltier effect, thereby improving energy efficiency. Among many thermoelectric materials, half-Heusler alloys have become a research hotspot for medium and high temperature thermoelectric materials due to their excellent mechanical properties and thermal stability.

[0003] Thermoelectric performance is defined by the thermoelectric figure of merit ZT, ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. Thermal conductivity is mainly determined by the lattice thermal conductivity κ L and the electronic thermal conductivity κ e Composition. The larger the thermoelectric figure of merit ZT, the better the thermoelectric performance. However, the thermoelectric parameters have a strong dependence on the carrier concentration and are coupled with each other. Taking the carrier concentration as the benchmark, they all change with the carrier concentration. Therefore, how to effectively decouple the thermoelectric parameters and improve ZT has always been one of the key scientific issues that need to be solved urgently in the field of thermoelectrics.

[0004] Among many half-Heusler alloys, NbFeSb-based half-Heusler materials have been developed as high-performance P-type thermoelectric materials due to their high Seebeck coefficient. At 1200K, their thermoelectric figure of merit (ZT value) has reached 1.6. High-efficiency and stable thermoelectric devices require that the thermal expansion coefficients of N-type and P-type thermoelectric materials match to avoid stress concentration causing device cracking. To this end, the development of N-type and P-type thermoelectric materials on the same matrix has always been a research hotspot in the field of thermoelectrics. However, compared with P-type NbFeSb-based half-Heusler materials, there are relatively few studies on N-type NbFeSb-based half-Heusler materials, and the gap in thermoelectric performance is large. Therefore, how to reduce the lattice thermal conductivity and improve the power factor to improve the thermoelectric performance of N-type NbFeSb alloys has become an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to propose an N-type NbFeSb-based half-Heusler thermoelectric material, which improves its thermoelectric performance by reducing the lattice thermal conductivity, in view of the problems that still need to be solved in the thermoelectric performance of current thermoelectric materials.

[0006] It should be noted that, in the present invention, unless otherwise specified, the specific meaning of "including" in relation to composition limitations and descriptions includes both open-ended "including", "comprising", etc. and similar meanings, as well as closed-ended "composed of", "composed of", etc. and similar meanings.

[0007] To achieve the above object, the technical solution adopted by the present invention is: an N-type NbFeSb-based half-Heusler thermoelectric material, whose general formula is Nb 1-X Cr X Fe 0.94 Co 0.06 Sb, where 0 <x≤0.3。

[0008] Furthermore, preferably, the x=0 <x≤0.03。

[0009] Furthermore, more preferably, x=0.01≤x≤0.03.

[0010] The N-type NbFeSb-based half-Heusler thermoelectric material of the present invention causes fluctuations in stress field and mass field by doping Cr elements, thereby enhancing phonon scattering, thereby reducing lattice thermal conductivity and improving thermoelectric performance.

[0011] Another object of the present invention is to disclose a method for preparing an N-type NbFeSb-based half-Heusler thermoelectric material, comprising the following steps:

[0012] The materials are weighed according to the general formula, placed in a magnetic levitation smelting furnace for smelting, the ingot obtained after smelting is placed in a planetary ball mill for ball milling, then filtered and dried to obtain powder, and the powder is sintered by discharge plasma to obtain N-type NbFeSb-based half-Heusler thermoelectric material.

[0013] Furthermore, the method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material comprises the following steps:

[0014] (1) Weighing Nb, Fe, Sb, Co and Cr raw materials according to the general formula;

[0015] (2) Place the raw materials in a magnetic suspension melting furnace and melt them in an argon atmosphere at a pressure of 10 4 ~10 5 Pa, melting temperature is 1600~1800℃, heat preservation is 20~40s;

[0016] (3) wet-milling the smelted ingot to obtain a wet powder with a particle size of 0.5 to 2 μm;

[0017] (4) drying the wet powder naturally;

[0018] (5) The powder is sintered by spark plasma sintering technology at a sintering temperature of 800 to 1000° C., a sintering pressure of 60 to 80 MPa, and a holding time of 5 to 20 minutes to obtain an N-type NbFeSb-based half-Heusler thermoelectric material.

[0019] Furthermore, the Nb, Fe, Sb, Co and Cr raw materials are small particles with a diameter of 0.5 to 10 mm.

[0020] Furthermore, the smelting times in step (2) is 3-7 times to ensure the uniformity of the structure after smelting.

[0021] Furthermore, the wet ball milling in step (3) includes: firstly crushing the ingot with a tablet press, and then performing wet ball milling, the ball milling medium is anhydrous ethanol, the ball-to-material ratio is 10:1-20:1, the rotation speed is 200-600 r / min, and the ball milling time is 5-20 hours.

[0022] Furthermore, the natural drying in step (4) includes: naturally drying the filtered powder in a glove box for 12-48 hours.

[0023] Furthermore, in step (5), the powder is sintered using spark plasma sintering technology, with a sintering temperature of 850° C., a sintering pressure of 65 MPa, and a holding time of 10 min.

[0024] Another purpose of the present invention is to disclose an application of N-type NbFeSb-based half-Heusler thermoelectric material in the fields of aerospace, new energy, and thermoelectric refrigeration: in the field of aerospace, the temperature difference between the inside and outside of the body can be used to power small electrical appliances worn on the body; radioisotope thermoelectric generators are also widely used in spacecraft; in new energy vehicles, thermoelectric materials can be used to absorb waste heat and convert it into electrical energy, thereby improving the utilization efficiency of automobile fuel; in the field of refrigeration, compressors or refrigerants such as Freon are not required as in traditional technologies.

[0025] The N-type NbFeSb-based half-Heusler thermoelectric material, preparation method and use thereof of the present invention have the following advantages compared with the prior art:

[0026] 1) The present invention obtains the N-type NbFeSb-based half-Heusler thermoelectric material by doping, and utilizes magnetic suspension melting and ball milling combined with spark plasma sintering process to prepare NbFe 0.94 Co 0.06Sb alloy is the master alloy. Cr is doped to replace Cr at the Nb position. Due to the large difference in radius and atomic mass, stress field and mass field fluctuations are caused, which effectively enhances phonon scattering, thereby reducing lattice thermal conductivity and improving the thermoelectric properties of N-type NbFeSb-based half-Heusler materials.

[0027] 2) The lattice thermal conductivity of the N-type NbFeSb-based half-Heusler thermoelectric material of the present invention is low.

[0028] 3) The N-type NbFeSb-based half-Heusler thermoelectric material of the present invention is suitable for aerospace, new energy, industry and other fields.

[0029] In summary, the present invention significantly reduces the lattice thermal conductivity of the NbFeSb-based half-Heusler material by doping the Cr element, thereby improving its thermoelectric performance. The material has excellent thermoelectric performance and thermal stability, and is suitable for medium and high temperature thermoelectric conversion applications, especially in the field of new energy, and has good application prospects and large-scale promotion potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Nb 1-X Cr X Fe 0.94 Co 0.06 XRD pattern of half-Heusler thermoelectric material of Sb (0≤x≤0.3);

[0031] Figure 2 Nb 1-X Cr X Fe 0.94 Co 0.06 Seebeck coefficient of half-Heusler thermoelectric material of Sb (0≤x≤0.3);

[0032] Figure 3 Nb 1-X Cr X Fe 0.94 Co 0.06 The conductivity of half-Heusler thermoelectric materials of Sb (0≤x≤0.3);

[0033] Figure 4 Nb 1-X Cr X Fe 0.94 Co 0.06 Total thermal conductivity of half-Heusler thermoelectric material of Sb (0≤x≤0.3);

[0034] Figure 5 Nb 1-XCr X Fe 0.94 Co 0.06 Lattice thermal conductivity of half-Heusler thermoelectric materials of Sb (0≤x≤0.3);

[0035] Figure 6 Nb 1-X Cr X Fe 0.94 Co 0.06 Thermoelectric figure of merit of half-Heusler thermoelectric materials of Sb (0≤x≤0.3). DETAILED DESCRIPTION

[0036] The present invention is further described below with reference to the examples. The description of the technical features described below is based on representative embodiments and specific examples of the present invention, but the present invention is not limited to these embodiments and specific examples. It should be noted that:

[0037] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0038] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0039] In the present specification, a numerical range expressed using "above" or "below" means a numerical range including the number.

[0040] In this specification, the word "may" means both performing a certain process and not performing a certain process.

[0041] In this specification, the use of "optional" or "optional" indicates that certain substances, components, execution steps, application conditions and other factors are used or not used.

[0042] In this specification, when "normal temperature" or "room temperature" is used, the temperature may be 15-25°C.

[0043] In this manual, the reagents or instruments used without indicating the manufacturer are all conventional products that can be obtained through commercial purchase.

[0044] This embodiment discloses an N-type half-Heusler thermoelectric material, the chemical composition of which is Nb 1- X Cr X Fe 0.94 Co 0.06 Sb; Nb 1-X Cr X Fe0.94 Co 0.06 The value range of x in Sb is 0≤x≤0.3;

[0045] The present invention also provides a method for preparing the above-mentioned N-type NbFeSb-based half-Heusler thermoelectric material, comprising the following steps:

[0046] Example 1

[0047] This embodiment discloses an N-type NbFeSb-based half-Heusler thermoelectric material, the general formula of which is Nb 0.99 Cr 0.01 Fe 0.94 Co 0.06 Sb, the preparation method thereof is as follows:

[0048] Material selection: Nb, Fe, Sb, Co, Cr are small particles with a diameter of 0.5 to 10 mm. The purity of all materials is ≥ 99.95%;

[0049] Ingredients: According to Nb 0.99 Cr 0.01 Fe 0.94 Co 0.06 The ingredients are prepared according to the stoichiometric ratio of Sb;

[0050] Melting: Melting in a magnetic suspension melting furnace, under an argon atmosphere, the pressure is 10 5 Pa. After heating to 1750℃, keep the temperature for 30s and repeat the smelting for 5 times to ensure the uniformity of the structure;

[0051] Ball milling: First, the ingot is crushed with a tablet press, and then wet ball milling is performed. The ball milling medium is anhydrous ethanol, the ball-to-material ratio is 15:1, the rotation speed is 500r / min, and the ball milling time is 12h.

[0052] Drying treatment: The filtered powder was naturally dried in a glove box for 48 hours.

[0053] Sintering: The powder is sintered by spark plasma sintering technology at a sintering temperature of 850° C., a sintering pressure of 65 MPa, and a holding time of 10 min to obtain an N-type NbFeSb-based half-Heusler thermoelectric material.

[0054] Example 2

[0055] This embodiment discloses an N-type NbFeSb-based half-Heusler thermoelectric material, the general formula of which is Nb 0.97 Cr 0.03 Fe 0.94 Co 0.06 Sb; its preparation method is the same as that in Example 1.

[0056] Comparative Example 1

[0057] This comparative example discloses a thermoelectric material having the general formula NbFe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0058] Comparative Example 2

[0059] This comparative example discloses a thermoelectric material having the general formula Nb 0.95 Cr 0.05 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0060] Comparative Example 3

[0061] This comparative example discloses a thermoelectric material having the general formula Nb 0.90 Cr 0.10 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0062] Comparative Example 4

[0063] This comparative example discloses a thermoelectric material having the general formula Nb 0.85 Cr 0.15 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0064] Comparative Example 5

[0065] This comparative example discloses a thermoelectric material having the general formula Nb 0.80 Cr 0.20 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0066] Comparative Example 6

[0067] This comparative example discloses a thermoelectric material having the general formula Nb 0.75 Cr 0.70 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0068] Comparative Example 7

[0069] This comparative example discloses a thermoelectric material having the general formula Nb 0.70 Cr 0.30 Fe 0.94 Co 0.06 Sb; the preparation method is the same as that in Example 1.

[0070] The thermoelectric materials of Examples 1-2 and Comparative Examples 1-7 were tested respectively, and the test results are as follows:

[0071] Nb 1-X Cr X Fe 0.94 Co 0.06 XRD patterns of half-Heusler thermoelectric materials of Sb (0≤x≤0.3) Figure 1 shown; from Figure 1 It can be seen that Nb 1-X Cr X Fe 0.94 Co 0.06 The half-Heusler thermoelectric material of Sb (0≤x≤0.3) has good peak matching and no other impurities.

[0072] Nb 1-X Cr X Fe 0.94 Co 0.06 The Seebeck coefficient of half-Heusler thermoelectric materials of Sb (0≤x≤0.3) is as follows Figure 2 shown; from Figure 2 It can be seen that the Seebeck coefficient is negative, indicating that Nb 1-X Cr X Fe 0.94 Co 0.06 The half-Heusler thermoelectric materials of Sb (0≤x≤0.3) all exhibit N-type electrical transport properties.

[0073] Nb 1-X Cr X Fe 0.94 Co 0.06 The conductivity of half-Heusler thermoelectric materials of Sb (0≤x≤0.3) is as follows Figure 3 shown; from Figure 3 It can be seen that with the increase of doping amount, the conductivity gradually increases.

[0074] Nb 1-X Cr X Fe 0.94 Co 0.06 The total thermal conductivity of the half-Heusler thermoelectric material of Sb (0≤x≤0.3) is as follows Figure 4 shown; from Figure 4 It can be seen that the total thermal conductivity gradually decreases with the increase of doping content, but when x=0.25 and 0.3, the bipolar diffusion effect occurs due to excessive doping. 0.99 Cr 0.01 Fe0.94 Co 0.06 The total thermal conductivity of the Sb-based thermoelectric material is 5.74 Wm -1 K -1 Compared with the half-Heusler alloy of Comparative Example 1 (6.20 Wm -1 K -1 ), decreased by 8% at 923K. The half-Heusler alloy Nb obtained in Example 2 0.97 Cr 0.03 Fe 0.94 Co 0.06 The total thermal conductivity of the Sb-based thermoelectric material is 5.29 Wm at 923 K. -1 K -1 , compared with the half-Heusler alloy NbFe prepared in Example 1 0.94 Co 0.06 Sb decreased by 15%.

[0075] Nb 1-X Cr X Fe 0.94 Co 0.06 The lattice thermal conductivity of half-Heusler thermoelectric materials of Sb (x = 0.01, 0.03) is as follows Figure 5 shown; from Figure 5 It can be seen that as the doping content gradually increases, the lattice thermal conductivity gradually decreases. The half-Heusler alloy obtained in Example 1 has a lower lattice thermal conductivity of 4.83 Wm -1 K -1 Compared with the half-Heusler alloy of comparative example 1 (5.29Wm -1 K -1 ), decreased by 8.2% at 923K. The half-Heusler alloy Nb obtained in Example 2 0.97 Cr 0.03 Fe 0.94 Co 0.06 The lattice thermal conductivity of the Sb-based thermoelectric material is 4.35 Wm at 923 K. -1 K -1 , compared with the half-Heusler alloy NbFe prepared in Example 1 0.94 Co 0.06 Sb decreased by 18%.

[0076] Nb 1-X Cr X Fe 0.94 Co 0.06 The thermoelectric figure of merit of half-Heusler thermoelectric materials of Sb (x = 0.01, 0.03) is as follows Figure 6shown; from Figure 6 It can be seen that the ZT of the half-Heusler alloy obtained in Example 1 is 0.25, which is 9% higher than that of the half-Heusler alloy (0.23) of Comparative Example 1 at 923K; ​​it is 9% higher than that of the half-Heusler alloy (0.23) of Comparative Example 2 at 923K; ​​it is 47% higher than that of the Half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 1.3% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 2.1% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 3.3% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 4.2% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 5.1% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​it is 6.1% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K. Compared with the half-Heusler alloy (0.12) of Example 4, it increased by 108% at 923K; ​​compared with the half-Heusler alloy (0.09) of Comparative Example 5, it increased by 177% at 923K; ​​compared with the half-Heusler alloy (0.06) of Comparative Example 6, it increased by 316% at 923K; ​​compared with the half-Heusler alloy (0.06) of Comparative Example 7, it increased by 316% at 923K. The half-Heusler alloy Nb obtained in Example 2 0.97 Cr 0.03 Fe 0.94 Co 0.06 The maximum ZT of the thermoelectric material with Sb component is 0.28 at 923K, which is higher than that of the half-Heusler alloy NbFe prepared in Example 1. 0.94 Co 0.06 Sb increased by 16%, which was 22% higher than that of the half-Heusler alloy (0.23) of Comparative Example 2 at 923K; ​​65% higher than that of the half-Heusler alloy (0.17) of Comparative Example 3 at 923K; ​​133% higher than that of the half-Heusler alloy (0.12) of Comparative Example 4 at 923K; ​​211% higher than that of the half-Heusler alloy (0.09) of Comparative Example 5 at 923K; ​​366% higher than that of the half-Heusler alloy (0.06) of Comparative Example 6 at 923K; ​​and 366% higher than that of the half-Heusler alloy (0.06) of Comparative Example 7 at 923K.

[0077] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An N-type NbFeSb-based half-Heusler thermoelectric material, characterized in that: Its general formula is Nb 1- X Cr X Fe 0.94 Co 0.06 Sb, where 0 <x≤0.3。 2. The N-type NbFeSb-based half-Heusler thermoelectric material according to claim 1, characterized in that: The x=0.01≤x≤0.

03.

3. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 1 or 2, characterized in that: The following steps are involved: The materials are weighed according to the general formula, placed in a magnetic levitation smelting furnace for smelting, the ingot obtained after smelting is placed in a planetary ball mill for ball milling, then filtered and dried to obtain powder, and the powder is sintered by discharge plasma to obtain N-type NbFeSb-based half-Heusler thermoelectric material.

4. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 3, characterized in that: The following steps are involved: (1) Weighing Nb, Fe, Sb, Co and Cr raw materials according to the general formula; (2) Place the raw materials in a magnetic suspension melting furnace and melt them in an argon atmosphere at a pressure of 10 4 ~10 5 Pa, melting temperature is 1600~1800℃, heat preservation is 20~40s; (3) wet-milling the smelted ingot to obtain a wet powder with a particle size of 0.5 to 2 μm; (4) drying the wet powder naturally; (5) The powder is sintered by spark plasma sintering technology at a sintering temperature of 800 to 1000° C., a sintering pressure of 60 to 80 MPa, and a holding time of 5 to 20 minutes to obtain an N-type NbFeSb-based half-Heusler thermoelectric material.

5. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 3 or 4, characterized in that: The Nb, Fe, Sb, Co and Cr raw materials are small particles with a diameter of 0.5 to 10 mm.

6. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 4, characterized in that: The number of smelting times in step (2) is 3-7 times.

7. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 4, characterized in that: The wet ball milling in step (3) comprises: firstly crushing the ingot with a tablet press, and then performing wet ball milling, wherein the ball milling medium is anhydrous ethanol, the ball-to-material ratio is 10:1-20:1, the rotation speed is 200-600 r / min, and the ball milling time is 5-20 hours.

8. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 4, characterized in that: The natural drying in step (4) comprises: naturally drying the filtered powder in a glove box for 12-48 hours.

9. The method for preparing the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 4, characterized in that: In step (5), the powder is sintered using spark plasma sintering technology, with a sintering temperature of 850° C., a sintering pressure of 65 MPa, and a holding time of 10 min.

10. Application of the N-type NbFeSb-based half-Heusler thermoelectric material according to claim 1 or 2 in the fields of aerospace, new energy and thermoelectric refrigeration.

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