P-type ZrCoSb-based thermoelectric material based on Sb bit entropy regulation and preparation method

Abstract

The invention discloses a p-type ZrCoSb-based thermoelectric material based on Sb bit entropy regulation and a preparation method, relates to the technical field of thermoelectric materials, and aims to solve the technical problem of low thermoelectric figure of merit of an existing half-Heusler alloy. The chemical formula of the p-type ZrCoSb-based thermoelectric material based on Sb bit entropy regulation and control is ZrCoSb < 0.8-x > Bi < x > Sn < 0.2 >, wherein x is not less than 0.05 and not more than 0.3; and at the temperature of 873 K, when x is equal to 0.2, the thermoelectric figure of merit of the thermoelectric material is 1.1. The preparation method of the thermoelectric material comprises the following steps: smelting zirconium, cobalt, antimony, bismuth and tin elementary substance raw materials in a protective atmosphere according to the composition proportion of each elementary substance to obtain an alloy ingot; crushing the alloy ingot, and performing grinding and ball milling treatment to obtain powder; and sintering the powder to obtain the thermoelectric material.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, and more specifically, to a p-type ZrCoSb-based thermoelectric material and a preparation method thereof based on Sb-site entropy regulation. Background Art

[0002] Thermoelectric materials can directly convert thermal energy and electrical energy based on their internal carrier transport characteristics. Thermoelectric materials and devices can achieve the effects of thermoelectric power generation and thermoelectric cooling through the Seebeck effect and the Peltier effect, respectively, and are currently applied in fields such as automotive exhaust waste heat power generation, isotope thermoelectric generators, small environmental protection refrigerators, and local cooling of precision instruments.

[0003] Half-Heusler (HH) alloys are a type of medium- and high-temperature thermoelectric materials, which have excellent electrical properties, mechanical properties, thermal stability, etc. Half-Heusler alloys have a face-centered cubic structure of MgAgAs, and the space group is F 3m, and the chemical formula is usually XYZ ; due to its highly symmetric crystal structure, this alloy has a relatively high power factor. For example, the power factor of ZrCoSb alloy at room temperature PF can reach 15 - 22 μWcm -1 K -2 . However, half-Heusler alloys also have a relatively high thermal conductivity. For example, the thermal conductivity of ZrCoSb alloy at room temperature k is 8 - 13 Wm -1 K -1 , resulting in a low thermoelectric figure of merit. Summary of the Invention

[0004] The purpose of the present invention is to provide a p-type ZrCoSb-based thermoelectric material and a preparation method thereof based on Sb-site entropy regulation to solve the technical problem of the low thermoelectric figure of merit of existing half-Heusler alloys. In view of this, the present invention is realized through the following solutions.

[0005] In the first aspect, the present invention provides a p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation, and the chemical formula of the thermoelectric material is ZrCoSb 0.8-x Bi x Sn 0.2 ; wherein, 0.05 ≤ x ≤ 0.3.

[0006] Compared with the prior art, for the p-type ZrCoSb-based thermoelectric material regulated by Sb-site entropy of the present invention, by doping tin (Sn) element at the antimony (Sb) site of the ZrCoSb alloy, the carrier concentration and power factor of the ZrCoSb alloy are initially improved; further, by doping bismuth (Bi) element at the antimony (Sb) site of the alloy, through the synergistic effect between tin (Sn) element and bismuth (Bi) element, and between these two elements and the remaining elements, the configurational entropy of the alloy is effectively improved; further, after doping tin (Sn) element and bismuth (Bi) element, the relatively complex or diverse chemical composition of the alloy will induce a large number of point defects and lattice distortions in it, enhancing the fluctuations of the mass field and stress field, thereby causing strong scattering of phonons and significantly reducing the lattice thermal conductivity of the alloy. The present invention conducts in-situ doping of tin (Sn) element and bismuth (Bi) element at the antimony (Sb) site in the ZrCoSb-based thermoelectric material, and precisely controls the content or proportion of each element within the above reasonable range after doping. After doping, each element can synergistically regulate the lattice thermal conductivity and electrical transport properties of the alloy, significantly improving the thermoelectric performance of the alloy (or material), and enabling the alloy (or material) to obtain a relatively high thermoelectric figure of merit. Experimental data according to any specific embodiment of the present invention show that within the entire temperature range, the p-type ZrCoSb-based thermoelectric material regulated by Sb-site entropy provided by the present invention has a relatively low thermal conductivity and a high power factor; specifically, the thermal conductivity of this thermoelectric material at room temperature is 3.90~5.83 Wm -1 K -1 , the power factor is 15~26 μWcm -1 K -2 , and at a temperature of 873 K, the thermoelectric figure of merit can reach up to 1.1 at most, having the characteristic of a high thermoelectric figure of merit. Through the above technical solution of the present invention, the technical problem that the existing half-Heusler alloy has a relatively high thermal conductivity, resulting in a low thermoelectric figure of merit, is solved.

[0007] In the second aspect, the present invention provides a preparation method of a thermoelectric material for preparing the above-mentioned p-type ZrCoSb-based thermoelectric material regulated by Sb-site entropy, including: Melting zirconium, cobalt, antimony, bismuth and tin elemental raw materials under a protective atmosphere condition according to the composition ratio of each elemental substance to obtain an alloy ingot; After crushing the alloy ingot, performing grinding and ball milling treatments to obtain a powder; Sintering the powder into a shape to obtain a thermoelectric material.

[0008] Compared with the prior art, the beneficial effects of the preparation method of the thermoelectric material of the present invention are the same as those of the above-mentioned p-type ZrCoSb-based thermoelectric material regulated by Sb-site entropy, and will not be elaborated here.

[0009] Further, in the preparation method of the thermoelectric material of the present invention, the zirconium elemental raw material is cylindrical particles, and the diameter × height of the cylindrical particles is (2~3) × (4~5) mm; and / or, the cobalt, antimony, and bismuth elemental raw materials are irregular particles, and the size of the particles is 1~5 mm; and / or, the tin elemental raw material is spherical particles, and the diameter of the spherical particles is 1~1.5 mm.

[0010] Further, in the preparation method of the thermoelectric material of the present invention, the melting is arc melting. During the arc melting process, the current is 200~400 mA, and the number of flips is 4~6 times.

[0011] Further, in the preparation method of the thermoelectric material of the present invention, during the melting process: Melting the zirconium elemental raw material and the cobalt elemental raw material to obtain a first alloy ingot; Melting the antimony, bismuth, and tin elemental raw materials to obtain a second alloy ingot; Fusing the first alloy ingot and the second alloy ingot to obtain a ZrCoSb 0.8-x Bi x Sn 0.2 alloy ingot.

[0012] Further, in the preparation method of the thermoelectric material of the present invention, the ball milling treatment is loaded in a glove box under argon protection. The ball-to-material ratio can be 5:1, the rotation speed can be 600~900 r / min, the ball milling time can be 3~4 h, and the cans are inverted once every 1~2 h of ball milling. Finally, a powder with a particle size of 0.5~2 μm is obtained.

[0013] Further, in the preparation method of the thermoelectric material of the present invention, the sintering and forming is spark plasma sintering and forming; during the spark plasma sintering and forming process, the powder is sintered by stepwise heating and stepwise cooling.

[0014] Further, in the preparation method of the thermoelectric material of the present invention, the spark plasma sintering and forming includes: Raising the temperature to a first intermediate temperature at a first heating rate; Raising the temperature from the first intermediate temperature to the sintering final temperature at a second heating rate; Performing heat preservation treatment at the sintering final temperature; Lowering the temperature from the sintering final temperature to a second intermediate temperature at a first cooling rate; Lowering the temperature from the second intermediate temperature to room temperature at a second cooling rate; Among them, a constant pressure is maintained during the spark plasma sintering and forming process.

[0015] Further, in the preparation method of the thermoelectric material of the present invention, the first heating rate is 70~90 °C / min, the first intermediate temperature is 850~920 °C, the second heating rate is 40~60 °C / min, and the final sintering temperature is 1000~1100 °C.

[0016] Further, in the preparation method of the thermoelectric material of the present invention, the first cooling rate is 30~50 °C / min, the second intermediate temperature is 600~650 °C, the second cooling rate is 60~100 °C / min, and the constant pressure is 40~60 MPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings described herein are used to provide a further understanding of the present invention, and constitute a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 is the XRD pattern of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 2 is the schematic diagram of the electrical conductivity of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 3 is the schematic diagram of the Seebeck coefficient of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 4 is the schematic diagram of the power factor of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 5 is the schematic diagram of the lattice thermal conductivity of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 6 is the schematic diagram of the thermal conductivity of the thermoelectric materials of the examples and comparative examples of the present invention; Figure 7 is the schematic diagram of the thermoelectric figure of merit of the thermoelectric materials of the examples and comparative examples of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0019] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality of" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0020] Half-Heusler (HH) alloys are mid- to high-temperature thermoelectric materials with excellent electrical, mechanical, and thermal stability properties. Half-Heusler alloys have a face-centered cubic structure of MgAgAs with a space group of F 3m, and the chemical formula is usually XYZ ; due to their highly symmetric crystal structure, these alloys have a relatively high power factor. For example, the power factor of the ZrCoSb alloy at room temperature PF can reach 15 - 22 μWcm -1 K -2 . However, half-Heusler alloys also have a relatively high thermal conductivity. For example, the thermal conductivity of the ZrCoSb alloy at room temperature k is 8 - 13 Wm -1 K -1 , resulting in a low figure of merit for thermoelectric performance.

[0021] To solve the above technical problems, in a first aspect, the present invention provides a p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation. The chemical formula of the thermoelectric material is ZrCoSb 0.8-x Bi x Sn 0.2 ; where 0.05 ≤ x ≤ 0.3.

[0022] In the case of adopting the above technical solution, for the p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation of the present invention, by doping tin (Sn) element at the antimony (Sb) site of the ZrCoSb alloy, the carrier concentration and power factor of the ZrCoSb alloy are initially increased; further, by doping bismuth (Bi) element at the antimony (Sb) site of the alloy, through the synergistic effect between the tin (Sn) element and the bismuth (Bi) element, and between these two elements and the remaining elements, the configurational entropy of the alloy is effectively increased; further, after doping with tin (Sn) element and bismuth (Bi) element, the relatively complex or diverse chemical composition of the alloy will induce a large number of point defects and lattice distortions, enhancing the fluctuations of the mass field and stress field, thereby causing strong scattering of phonons and significantly reducing the lattice thermal conductivity of the alloy. The present invention conducts in-situ doping of tin (Sn) element and bismuth (Bi) element at the antimony (Sb) site in the ZrCoSb-based thermoelectric material, and precisely controls the content or ratio of each element within the above reasonable range after doping. After doping, each element can synergistically regulate the lattice thermal conductivity and electrical transport properties of the alloy, significantly improving the thermoelectric performance of the alloy (or material), and enabling the alloy (or material) to obtain a high thermoelectric figure of merit. Experimental data according to any specific embodiment of the present invention show that, within the entire temperature range, the p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation provided by the present invention has a relatively low thermal conductivity and a high power factor; specifically, the thermal conductivity of this thermoelectric material at room temperature is 3.90~5.83 Wm -1 K -1 , and the power factor is 15~26 μWcm -1 K -2 , and at a temperature of 873 K, the highest thermoelectric figure of merit can reach 1.1, having the characteristic of a high thermoelectric figure of merit. Through the above technical solution of the present invention, the technical problem that the existing half-Heusler alloy has a high thermal conductivity, resulting in a low thermoelectric figure of merit, is solved.

[0023] In the second aspect, the present invention provides a preparation method of a thermoelectric material for preparing the above p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation, including: Melting zirconium, cobalt, antimony, bismuth, and tin elemental raw materials under a protective atmosphere condition according to the composition ratio of each elemental substance to obtain an alloy ingot; After crushing the alloy ingot, performing grinding and ball milling treatments to obtain a powder; Sintering the powder into a shape to obtain a thermoelectric material.

[0024] In the case of adopting the above technical solution, in the preparation method of the thermoelectric material of the present invention, according to the composition ratio of the elemental substances, zirconium, cobalt, antimony, bismuth and tin elemental substance raw materials are melted under a protective atmosphere condition to obtain an alloy ingot. After that, the alloy ingot is crushed, and then subjected to grinding and ball milling treatments to obtain a powder, and then the powder is sintered and formed to obtain the above thermoelectric material.

[0025] It should be understood that in order to make the performance of the prepared thermoelectric material more stable and facilitate the weighing process of each elemental substance raw material, the specifications of each elemental substance raw material are also limited in the preparation method of the thermoelectric material of the present invention; by way of example, the zirconium elemental substance raw material is cylindrical particles, and the diameter × height of the cylindrical particles is (2~3)×(4~5) mm; the cobalt, antimony and bismuth elemental substance raw materials are irregular particles, and the size of the particles is 1~5 mm; the tin elemental substance raw material is spherical particles, and the diameter of the spherical particles is 1~1.5 mm.

[0026] It should also be understood that in the preparation method of the thermoelectric material of the present invention, during the arc melting process, the conditions or parameters of the arc melting should also be controlled within a reasonable range to obtain a thermoelectric material with stable performance; by way of example, during the arc melting process, the current can be 200~400 mA, and the number of flipping times can be 4~6 times; in another example, the current can be 200 mA, 300 mA or 400 mA, and the number of flipping times can be 4 times, 5 times or 6 times.

[0027] As a possible implementation manner, in the preparation method of the thermoelectric material of the present invention, during the melting process: Melt the zirconium elemental substance raw material and the cobalt elemental substance raw material to obtain a first alloy ingot; Melt the antimony, bismuth and tin elemental substance raw materials to obtain a second alloy ingot; Melt the first alloy ingot and the second alloy ingot together to obtain a ZrCoSb 0.8-x Bi x Sn 0.2 alloy ingot.

[0028] In the case of adopting the above technical solution, in the preparation method of the thermoelectric material of the present invention, the zirconium and cobalt elemental substance raw materials are melted separately from the antimony, bismuth and tin elemental substance raw materials, avoiding the problem of volatilization of antimony and / or bismuth elements caused by melting all the elemental substance raw materials together. By way of example, during the preparation process of the thermoelectric material, considering the volatilization factor of antimony element and compensating for its volatilization loss, 5 wt% of antimony element is additionally added.

[0029] Furthermore, in the preparation method of the thermoelectric material of the present invention, it is impossible to obtain powders with relatively uniform particle sizes only by grinding treatment. By grinding and ball-milling the alloy ingot after crushing treatment, on the one hand, the crystal grains can be reduced and the number of grain boundaries can be increased, which is beneficial to phonon scattering and reduces the lattice thermal conductivity; on the other hand, the powders (or components) can be made more uniform, avoiding composition segregation during the traditional melting process; on the third hand, after ball-milling treatment, a denser material structure can be formed during the spark plasma sintering (SPS) process, significantly reducing the porosity of the prepared thermoelectric material and improving the overall performance of the thermoelectric material. By way of example, the ball-milling treatment can be loaded in a glove box under argon protection. The ball-to-material ratio can be 5:1, the rotation speed can be 600 - 900 r / min, the ball-milling time can be 3 - 4 h, and the cans need to be inverted once every 1 - 2 h of ball-milling. Finally, powders with a particle size of 0.5 - 2 μm are obtained. As another example, the rotation speed can be 600 r / min, 800 r / min or 900 r / min, the ball-milling time can be 3 h or 4 h, and the cans need to be inverted once every 1 h, 1.5 h or 2 h of ball-milling.

[0030] As a possible implementation manner, in the preparation method of the thermoelectric material of the present invention, the sintering is spark plasma sintering; during the spark plasma sintering process, the powders are sintered by stepwise heating and stepwise cooling.

[0031] In the case of adopting the above technical solution, in the preparation method of the thermoelectric material of the present invention, sintering the powder by stepwise heating can significantly improve the density of the material and reduce the porosity of the material; since the thermoelectric material (i.e., the prepared alloy) of the present invention is relatively brittle, when rapidly cooled, the surface of the alloy shrinks first, while the interior is still in a high-temperature expansion state, resulting in uneven internal and external shrinkage, causing the thermal stress to exceed its fracture strength, leading to cracking or fragmentation of the thermoelectric material. By stepwise cooling, this situation can be avoided, thereby preparing a thermoelectric material with more stable performance. Exemplarily, the spark plasma sintering forming can be: heating the temperature to a first intermediate temperature at a first heating rate; heating the temperature from the first intermediate temperature to the sintering final temperature at a second heating rate; performing a heat preservation treatment at the sintering final temperature; cooling the temperature from the sintering final temperature to a second intermediate temperature at a first cooling rate; cooling the temperature from the second intermediate temperature to room temperature at a second cooling rate; wherein, a constant pressure is maintained during the spark plasma sintering forming process. Another exemplarily, the first heating rate is 70 - 90 °C / min, the first intermediate temperature is 850 - 920 °C, the second heating rate is 40 - 60 °C / min, the sintering final temperature is 1000 - 1100 °C, the first cooling rate is 30 - 50 °C / min, the second intermediate temperature is 600 - 650 °C, the second cooling rate is 60 - 100 °C / min, and the constant pressure is 40 - 60 MPa. Still another exemplarily, the first heating rate can be 70 °C / min, 80 °C / min or 90 °C / min, the first intermediate temperature can be 850 °C, 880 °C or 920 °C, the second heating rate can be 40 °C / min, 50 °C / min or 60 °C / min, the sintering final temperature can be 1000 °C, 1050 °C or 1100 °C, the first cooling rate can be 30 °C / min, 40 °C / min or 50 °C / min, the second intermediate temperature can be 600 °C, 630 °C or 650 °C, the second cooling rate can be 60 °C / min, 80 °C / min or 100 °C / min, the constant pressure can be 40 MPa, 50 MPa or 60 MPa, and the room temperature can be 25 °C.

[0032] To better understand the present invention, the content of the present invention will be further clarified below in conjunction with specific embodiments, but the content of the present invention is not limited to the following embodiments only.

[0033] The raw materials used in the following embodiments are all commercially available raw materials unless otherwise specified.

[0034] Example 1

[0035] In the first aspect, this embodiment provides a p-type ZrCoSb-based thermoelectric material regulated by Sb-site entropy. This thermoelectric material belongs to the half-Heusler thermoelectric material, and its chemical formula is ZrCoSb 0.75 Bi 0.05 Sn 0.2 .

[0036] In the second aspect, this embodiment provides a preparation method of the above ZrCoSb 0.75 Bi 0.05 Sn 0.2 , including: S100, after weighing each elemental single-substance raw material according to the composition ratio of each element (the single-substance raw materials are zirconium Zr, cobalt Co, antimony Sb, bismuth Bi, and tin Sn single-substance raw materials respectively), place them in an arc melting furnace; in order to avoid the volatilization of antimony Sb, an additional 5% of antimony Sb single-substance raw material is added in this embodiment; S200, divide the zirconium Zr and cobalt Co single-substance raw materials into the first group, and the remaining single-substance raw materials into the second group, and perform arc melting separately under argon protection; among them: The first group prepares a Zr-Co alloy ingot at a melting current of 300 mA, and the second group prepares an Sb-Bi-Sn alloy ingot under the same parameters; perform a combined melting treatment on the two alloy ingots, maintain a melting current of 400 mA, and after 4 times of flipping and melting, obtain a ZrCoSb 0.75 Bi 0.05 Sn 0.2 alloy ingot; S300, crush the ZrCoSb 0.75 Bi 0.05 Sn 0.2 alloy ingot, and coarsely grind it into a powder with a particle size of 0.1 - 1 mm in a mortar under atmospheric environmental conditions; S400, in a glove box under argon protection, place the ground powder in a ball milling jar, and under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 600 r / min, and a ball milling time of 3 h (it is necessary to perform a jar inversion every 1 h of ball milling), ball mill to obtain a ZrCoSb 0.75 Bi 0.05 Sn 0.2 powder with a particle size of 0.5 - 2 μm; S500, place the ZrCoSb 0.75 Bi 0.05 Sn 0.2 powder in a graphite mold, heat it to 850 °C in 10 min, then heat it to 1000 °C at a rate of 50 °C / min, keep it warm for 10 min, then cool it to 600 °C in 10 min, and cool it to room temperature (25 °C) at a rate of 70 °C / min, and keep the pressure at 40 MPa throughout the process to prepare the thermoelectric material ZrCoSb0.75 Bi 0.05 Sn 0.2 。

[0037] Example 2

[0038] In a first aspect, this example provides a p-type ZrCoSb-based thermoelectric material regulated by Sb site entropy. This thermoelectric material belongs to the half-Heusler thermoelectric material, and its chemical formula is ZrCoSb 0.7 Bi 0.1 Sn 0.2 。

[0039] In a second aspect, this example provides a preparation method for the above ZrCoSb 0.7 Bi 0.1 Sn 0.2 which includes: S100, After weighing each elemental raw material according to the composition ratio of each elemental substance (zirconium Zr, cobalt Co, antimony Sb, bismuth Bi, and tin Sn elemental raw materials respectively), place them in an arc melting furnace; in order to avoid the volatilization of antimony Sb, an additional 5% of antimony Sb elemental raw material is added in this example; S200, Divide the zirconium Zr and cobalt Co elemental raw materials into the first group, and the remaining elemental raw materials into the second group, and carry out arc melting separately under argon protection; among them: The first group prepares a Zr-Co alloy ingot at a melting current of 400 mA, and the second group prepares an Sb-Bi-Sn alloy ingot under the same parameters; fuse the two alloy ingots together, maintain a melting current of 300 mA, and after 5 times of flipping melting, obtain a ZrCoSb 0.7 Bi 0.1 Sn 0.2 alloy ingot; S300, Crush the ZrCoSb 0.7 Bi 0.1 Sn 0.2 alloy ingot, and under atmospheric environmental conditions, coarsely grind it into a powder with a particle size of 0.1 - 1 mm using a mortar; S400, In a glove box under argon protection, place the ground powder in a ball milling tank, and under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 800 r / min, and a ball milling time of 4 h (it is necessary to perform a tank inversion every 2 h of ball milling), ball mill to obtain a ZrCoSb 0.7 Bi 0.1 Sn 0.2 powder; S500, The ZrCoSb 0.7 Bi 0.1 Sn 0.2The powder is placed in a graphite mold, heated to 900 °C in 10 min, then heated to 1050 °C at a rate of 50 °C / min, held at this temperature for 10 min, cooled to 650 °C in 7 min, and then cooled to room temperature (25 °C) at a rate of 70 °C / min. The pressure is maintained at 60 MPa throughout the process to obtain the thermoelectric material ZrCoSb 0.7 Bi 0.1 Sn 0.2 。

[0040] Example 3

[0041] In a first aspect, this example provides a p-type ZrCoSb-based thermoelectric material based on entropy regulation of the Sb site. This thermoelectric material belongs to the half-Heusler thermoelectric material, and its chemical formula is ZrCoSb 0.6 Bi 0.2 Sn 0.2 。

[0042] In a second aspect, this example provides a preparation method for the above ZrCoSb 0.6 Bi 0.2 Sn 0.2 , including: S100, after weighing the elemental raw materials according to the composition ratio of each elemental substance (the elemental raw materials are zirconium Zr, cobalt Co, antimony Sb, bismuth Bi, and tin Sn elemental substances respectively), place them in an arc melting furnace; in order to avoid the volatilization of antimony Sb, an additional 5% of antimony Sb elemental raw material is added in this example; S200, divide the zirconium Zr and cobalt Co elemental raw materials into the first group, and the remaining elemental raw materials into the second group, and perform arc melting separately under argon protection; among them: The first group prepares a Zr-Co alloy ingot at a melting current of 400 mA, and the second group prepares an Sb-Bi-Sn alloy ingot under the same parameters; the two alloy ingots are subjected to a combined melting treatment, maintaining a melting current of 200 mA, and after 6 times of flipping and melting, a ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy ingot with uniform composition is obtained; S300, crush the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy ingot, and in an atmospheric environment, coarsely grind it into a powder with a particle size of 0.1 - 1 mm using a mortar; S400, in a glove box under argon protection, place the ground powder in a ball milling tank, and under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 900 r / min, and a ball milling time of 3 h (the tank needs to be inverted once every 1 h of ball milling), ball mill to obtain ZrCoSb with a particle size of 0.5 - 2 μm 0.6 Bi0.2 Sn 0.2 Powder S500, place ZrCoSb 0.6 Bi 0.2 Sn 0.2 The powder is placed in a graphite mold, heated to 920 °C in 13 min, then heated to 1000 °C at a rate of 40 °C / min, held for 15 min, cooled to 600 °C in 10 min, and cooled to room temperature (25 °C) at a rate of 60 °C / min. The pressure is maintained at 50 MPa throughout the process to prepare the thermoelectric material ZrCoSb 0.6 Bi 0.2 Sn 0.2 .

[0043] Example 4

[0044] First, this example provides a p-type ZrCoSb-based thermoelectric material based on Sb-site entropy regulation. This thermoelectric material belongs to the half-Heusler thermoelectric material, and its chemical formula is ZrCoSb 0.5 Bi 0.3 Sn 0.2 .

[0045] Second, this example provides the preparation method of the above ZrCoSb 0.5 Bi 0.3 Sn 0.2 , including: S100, weigh each elemental raw material (zirconium Zr, cobalt Co, antimony Sb, bismuth Bi, and tin Sn elemental raw materials respectively) according to the composition ratio of each element, and then place them in an arc melting furnace; in order to avoid the volatilization of antimony Sb, 5% of antimony Sb elemental raw material is additionally added in this example; S200, divide the zirconium Zr and cobalt Co elemental raw materials into the first group, and the remaining elemental raw materials into the second group, and carry out arc melting respectively under argon protection; among them: The first group prepares a Zr-Co alloy ingot at a melting current of 300 mA, and the second group prepares an Sb-Bi-Sn alloy ingot under the same parameters; the two alloy ingots are subjected to a combined melting treatment, maintaining a melting current of 200 mA, and after 5 times of flipping melting, a ZrCoSb 0.5 Bi 0.3 Sn 0.2 alloy ingot is obtained; S300, crush the ZrCoSb 0.5 Bi 0.3 Sn 0.2 alloy ingot, and under the atmospheric environment conditions, coarsely grind it into a powder with a particle size of 0.1~1 mm with a mortar; S400. In a glove box under argon protection, place the ground powder in a ball milling jar. Under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 800 r / min, and a ball milling time of 3 h (inverting the jar once every 1.5 h of ball milling), ball mill to obtain ZrCoSb powder with a particle size of 0.5 - 2 μm 0.5 Bi 0.3 Sn 0.2 powder; S500. Place the ZrCoSb 0.5 Bi 0.3 Sn 0.2 powder in a graphite mold. Heat it to 900 °C in 13 min, then heat it to 1100 °C at a rate of 50 °C / min, hold for 15 min, then cool it to 650 °C in 10 min, and cool it to room temperature (25 °C) at a rate of 70 °C / min. Keep the pressure at 60 MPa throughout the process to prepare the thermoelectric material ZrCoSb 0.5 Bi 0.3 Sn 0.2 .

[0046] Comparative Example 1 This comparative example prepared a half-Heusler thermoelectric material ZrCoSb. The preparation process included: Step 1. Weigh the elemental raw materials according to ZrCoSb (to avoid the volatilization of antimony Sb, an additional 5% of antimony Sb element is added to the raw materials). Place them in an arc melting furnace and carry out arc melting under argon protection. Keep the melting current at 300 mA and obtain a ZrCoSb alloy ingot with uniform composition after 4 times of flipping melting; Step 2. Crush the ZrCoSb alloy ingot and coarsely grind it into powder with a particle size of 0.1 - 1 mm in a mortar under atmospheric conditions; Step 3. In a glove box under argon protection, place the ground powder in a ball milling jar. Under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 600 r / min, and a ball milling time of 4 h (inverting the jar once every 2 h of ball milling), ball mill to obtain ZrCoSb powder with a particle size of 0.5 - 2 μm; Step 4. Place the ZrCoSb powder in a graphite mold. Heat it to 850 °C in 10 min, then heat it to 1000 °C at a rate of 50 °C / min, hold for 10 min, then cool it to 600 °C in 10 min, and cool it to room temperature at a rate of 100 °C / min. Keep the pressure at 40 MPa throughout the process to obtain the thermoelectric material ZrCoSb.

[0047] Comparative Example 2 This comparative example prepared a half-Heusler thermoelectric material ZrCoSb0.8 Sn 0.2 The preparation process includes: Step 1: According to ZrCoSb 0.8 Sn 0.2 Weigh the elemental preparation raw materials (in order to avoid the volatilization of antimony Sb, an additional 5% of antimony Sb element is added to the preparation raw materials), place them in an arc melting furnace, divide the zirconium Zr, cobalt Co elemental substances and antimony Sb, tin Sn elemental substances into two groups of raw materials, and carry out arc melting separately under argon protection: the first group prepares a Zr-Co alloy ingot at a melting current of 300 mA, and the second group prepares an Sb-Sn alloy ingot under the same parameters; fuse the two groups of ingots, keep the melting current of 300 mA, and obtain a ZrCoSb 0.8 Sn 0.2 alloy ingot with uniform composition after 5 times of flipping and melting; Step 2: Crush the ZrCoSb 0.8 Sn 0.2 alloy ingot, and coarsely grind it into a powder with a particle size of 0.1 - 1 mm in a mortar under atmospheric conditions; Step 3: In a glove box under argon protection, place the ground powder in a ball milling tank, and ball mill it under the conditions of a ball-to-material ratio of 5:1, a rotation speed of 600 r / min, and a ball milling time of 3 h (the tank needs to be inverted once every 1 h of ball milling) to obtain a ZrCoSb 0.8 Sn 0.2 powder with a particle size of 0.5 - 2 μm; Step 4: Place the ZrCoSb 0.8 Sn 0.2 powder in a graphite mold, heat it to 920 °C in 13 min, then heat it to 1000 °C at a rate of 50 °C / min, keep it for 15 min, cool it to 650 °C in 10 min, and cool it to room temperature at a rate of 70 °C / min, and keep the pressure at 50 MPa throughout to obtain the thermoelectric material ZrCoSb 0.8 Sn 0.2 .

[0048] In the above embodiments or comparative examples of the present invention, the zirconium elemental raw material is a cylindrical particle, and the diameter × height of the cylindrical particle is 3 × 5 mm; the cobalt, antimony, and bismuth elemental raw materials are irregular particles, and the size of the particles is 1 - 5 mm; the tin elemental raw material is a spherical particle, and the diameter of the spherical particle is 1.5 mm.

[0049] Please refer to Figures 1 to 7 , the following will further explain the ZrCoSb Figures 1 to 7 of the present invention 0.8-x Bi x Sn 0.2 , thermoelectric material. FromFigure 1 It can be seen that the alloys prepared in the examples and comparative examples of the present invention have all formed the HH phase, and only the ZrCoSb in Example 4 0.5 Bi 0.3 Sn 0.2 alloy shows a small amount of ZrCo2 impurity phase. With the addition of the elements of tin (Sn) and bismuth (Bi), the diffraction peak corresponding to the (220) crystal plane in the spectrum gradually shifts to a lower angle. The lattice constants of each sample are obtained through Rietveld refinement calculation of the XRD spectrum. The lattice constant of the sample increases from 6.0809 ( x =0) to 6.1065 ( x =0.3). The change in the lattice parameter indicates that the elements of tin (Sn) and bismuth (Bi) have been dissolved in the HH phase to form a single-phase solid solution. From Figure 2 、 Figure 3 and Figure 4 it can be seen that the ZrCoSb alloy obtained in Comparative Example 1 has the lowest conductivity and Seebeck coefficient. After doping with the element of tin (Sn), both the conductivity and the Seebeck coefficient increase, resulting in a significant increase in the power factor. At a temperature of 873 K, the power factor reaches 29 μWcm -1 K -2 ; On the basis of the composition of Comparative Example 2, continue to dope with the element of bismuth (Bi) to form ZrCoSb 0.8-x Bi x Sn 0.2 alloy. Its conductivity increases with the increase of the doping amount x , and the Seebeck coefficient decreases with the increase of the doping amount x . At a temperature of 873 K, the ZrCoSb 0.7 Bi 0.1 Sn 0.2 alloy obtained in Example 2 and the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy obtained in Example 3 both have a power factor exceeding that of the ZrCoSb 0.8 Sn 0.2 alloy obtained in Comparative Example 2. Among them, the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy obtained in Example 3 has the highest power factor. At a temperature of 873 K, the power factor is 37.8 μWcm -1 K -2 , which is about 40% higher than that of the ZrCoSb 0.8 Sn 0.2 alloy obtained in Comparative Example 2; Therefore, the technical solution of the present invention is beneficial to optimizing the power factor of the ZrCoSb alloy. FromFigure 5 It can be seen that the lattice thermal conductivities of the ZrCoSb alloy obtained in Comparative Example 1 and the ZrCoSb 0.8 Sn 0.2 alloy at a temperature of 873 K are 4.13 Wm -1 K -1 and 5.22 Wm -1 K -1 respectively; after introducing the bismuth (Bi) element, the tin (Sn) element and the bismuth (Bi) element jointly increase the configurational entropy of the alloy, and the complex chemical composition induces a large number of point defects and lattice distortions in the material, enhancing the fluctuations of the mass field and the stress field, thereby causing strong scattering of phonons and significantly reducing the lattice thermal conductivity of the material; at a temperature of 873 K, the lattice thermal conductivities of Examples 1 to 4 are significantly lower than those of Comparative Examples 1 and 2. Among them, the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy obtained in Example 3 has the lowest lattice thermal conductivity, which is 1.88 Wm -1 K -1 at a temperature of 873 K, which is decreased by about 60% compared with the ZrCoSb 0.8 Sn 0.2 alloy obtained in Comparative Example 2; therefore, the technical solution of the present invention is beneficial to reducing the lattice thermal conductivity of the ZrCoSb alloy. From Figure 6 It can be seen that the thermal conductivities of the ZrCoSb alloy obtained in Comparative Example 1 and the ZrCoSb 0.8 Sn 0.2 alloy at a temperature of 873 K are 4.20 Wm -1 K -1 and 5.81 Wm -1 K -1 respectively. The thermal conductivities of the alloys obtained in the comparative examples and the examples mainly depend on the lattice thermal conductivity. At a temperature of 873 K, the thermal conductivities of Examples 1 to 4 are significantly lower than those of Comparative Examples 1 and 2. Among them, the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy obtained in Example 3 has the lowest thermal conductivity, which is 2.98 Wm -1 K -1 at a temperature of 873 K, which is decreased by about 50% compared with the ZrCoSb 0.8 Sn 0.2 alloy obtained in Comparative Example 2. From Figure 7 It can be seen that the ZrCoSb alloy obtained in Comparative Example 1 and the ZrCoSb 0.8 Sn 0.2The thermoelectric figure of merit of the alloy at a temperature of 873 K is 0.02 and 0.45 respectively, while the ZrCoSb obtained in Examples 1 to 4 0.8-x Bi x Sn 0.2 alloy (0.05 ≤ x ≤ 0.3) has a higher thermoelectric figure of merit than the ZrCoSb obtained in Comparative Example 2 0.8 Sn 0.2 alloy; further, with the increase of the doping amount x of the ZrCoSb obtained in Examples 1 to 4 0.8-x Bi x Sn 0.2 alloy (0.05 ≤ x ≤ 0.3), the thermoelectric figure of merit first increases and then decreases. At a temperature of 873 K, the ZrCoSb 0.6 Bi 0.2 Sn 0.2 alloy obtained in Example 3 has the largest thermoelectric figure of merit, reaching 1.1, which is mainly due to the decrease of lattice thermal conductivity and the increase of power factor.

[0050] In the description of the above embodiments, specific features, structures, materials or characteristics can be combined in a suitable manner in any one or more embodiments or examples.

[0051] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, and all of them should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A p-type ZrCoSb-based thermoelectric material based on Sb position entropy regulation, characterized in that: The chemical formula of the thermoelectric material is ZrCoSb 0.8-x Bi x Sn 0.2 ; Among them, 0.05≤ x ≤0.

3.

2. A method for preparing a thermoelectric material, characterized in that: The method for preparing the p-type ZrCoSb-based thermoelectric material based on Sb position entropy regulation according to claim 1 comprises: According to the composition ratio of each element, zirconium, cobalt, antimony, bismuth and tin are smelted under protective atmosphere to obtain alloy ingots; The alloy ingot is crushed, and then ground and ball-milled to obtain powder; The powder is sintered to obtain a thermoelectric material.

3. The method for preparing a thermoelectric material according to claim 2, characterized in that: The zirconium single substance raw material is a cylindrical particle, and the diameter×height of the cylindrical particle is (2-3)×(4-5) mm; And / or, the cobalt, antimony and bismuth single substance raw materials are irregular particles, and the size of the particles is 1-5 mm; And / or, the tin single substance raw material is spherical particles, and the diameter of the spherical particles is 1-1.5 mm.

4. The method for preparing a thermoelectric material according to claim 2, characterized in that: The smelting is arc smelting. During the arc smelting process, the current is 200-400 mA and the number of flipping times is 4-6 times.

5. The method for preparing a thermoelectric material according to claim 2 or 4, characterized in that: During the smelting process: Smelting a zirconium single substance raw material and a cobalt single substance raw material to obtain a first alloy ingot; Smelting the single element raw materials of antimony, bismuth and tin to obtain a second alloy ingot; The first alloy ingot and the second alloy ingot are melted together to obtain ZrCoSb 0.8-x Bi x Sn 0.2 Alloy ingot.

6. The method for preparing a thermoelectric material according to claim 2, characterized in that: The ball milling treatment is carried out in a glove box under argon protection conditions, with a ball-to-material ratio of 5:1, a rotation speed of 600-900 r / min, a ball milling time of 3-4 h, and a can inversion every 1-2 h of ball milling, and finally a powder with a particle size of 0.5-2 μm is obtained.

7. The method for preparing a thermoelectric material according to claim 2, characterized in that: The sintering molding is spark plasma sintering molding; during the spark plasma sintering molding process, the powder is sintered by step-by-step heating and step-by-step cooling.

8. The method for preparing a thermoelectric material according to claim 7, characterized in that: The spark plasma sintering forming comprises: Raising the temperature to a first intermediate temperature at a first heating rate; increasing the temperature from the first intermediate temperature to the sintering final temperature at a second heating rate; Performing heat preservation treatment at the final sintering temperature; Lowering the temperature from the sintering final temperature to a second intermediate temperature at a first cooling rate; reducing the temperature from the second intermediate temperature to room temperature at a second cooling rate; Wherein, the spark plasma sintering molding process maintains a constant pressure.

9. The method for preparing a thermoelectric material according to claim 8, characterized in that: The first heating rate is 70-90°C / min, the first intermediate temperature is 850-920°C, the second heating rate is 40-60°C / min, and the final sintering temperature is 1000-1100°C.

10. The method for preparing a thermoelectric material according to claim 8, characterized in that: The first cooling rate is 30-50°C / min, the second intermediate temperature is 600-650°C, the second cooling rate is 60-100°C / min, and the constant pressure is 40-60 MPa.

Images