Thermoelectric material and preparation method thereof

Abstract

The invention discloses a thermoelectric material and a preparation method thereof, the chemical formula of the thermoelectric material is K2Bi8 + xS13, the thermoelectric material is n-type, and x is more than 0 and less than or equal to 0.004. The preparation method of the thermoelectric material comprises the following steps: (1) a high-temperature smelting step: in a vacuum environment, performing high-temperature smelting treatment on raw materials weighed according to a stoichiometric ratio to obtain a K2Bi8 + xS13 cast ingot; and (2) a densification step: grinding the K2Bi8 + xS13 cast ingot into powder, and performing spark plasma sintering treatment on the powder under a vacuum condition to obtain a K2Bi8 + xS13 thermoelectric material block, wherein the spark plasma sintering treatment is carried out under the pressure of 40 to 50 MPa. The K2Bi8 + xS13 thermoelectric material disclosed by the invention has good conductivity and Seebeck coefficient and relatively low lattice thermal conductivity, and has a good application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of high-performance thermoelectric material preparation, and particularly relates to a thermoelectric material and a preparation method thereof. BACKGROUND

[0002] To meet the growing needs of technology and industry, the demand for advanced functional materials is increasing. Considering the global energy crisis of oil, natural gas and power shortage that the world is experiencing, it is very important to further study functional materials.

[0003] Thermoelectric materials are a kind of functional materials that realize direct conversion between heat and electricity by using the movement of carriers inside the solid. Today, it is of great practical significance to study new thermoelectric materials. Thermoelectric technology provides a simple and environmentally friendly solution for the direct conversion of waste heat, especially low-grade (<300℃) waste heat, to electricity, and is currently an effective way to realize waste heat recycling. Thermoelectric conversion technology has the advantages of small size, zero emission, and no noise, and has unique advantages in heat management and small device power supply.

[0004] Therefore, it is necessary to provide a new thermoelectric material with good electrical properties. SUMMARY

[0005] In view of this, the present application proposes a new n-type K2Bi 8+x S 13 Thermoelectric material, which has good electrical conductivity and Seebeck coefficient, and low lattice thermal conductivity, significantly improving the thermoelectric performance of the thermoelectric material.

[0006] The present application adopts the following technical solutions:

[0007] An n-type K2Bi 8+x S 13 Thermoelectric material, the chemical formula is K2Bi 8+x S 13 , wherein 0 < x < 0.004.

[0008] Preferably, the value of x is 0, 0.001, 0.002, 0.003, 0.004.

[0009] A preparation method of an n-type K2Bi 8+x S 13 Thermoelectric material, specifically comprising the following steps:

[0010] (1) High-temperature smelting step: in a vacuum environment, the raw materials weighed according to the stoichiometric ratio are subjected to high-temperature smelting treatment to obtain K2Bi 8+x S 13Ingot casting; the high-temperature smelting process is at a temperature of 873-1073 K and a holding time of 72-82 h;

[0011] (2) Densification step: the K2Bi 8+x S 13 The ingot is ground into powder, and the powder is subjected to a spark plasma sintering process for 10-20 min under vacuum to obtain K2Bi 8+x S 13 Thermoelectric material block; wherein the spark plasma sintering process is carried out under a pressure of 40-50 MPa.

[0012] Preferably, the high-temperature smelting process is carried out in a sealed reaction tube with a vacuum degree of not more than Pa.

[0013] Preferably, the reaction tube is a carbon-coated quartz tube, and the thickness of the carbon coating on the quartz tube is 50-200 nm, which is used to prevent the raw materials from reacting with the quartz tube at high temperatures.

[0014] Preferably, the high-temperature smelting process has a heating rate of 11-18 K / h and a cooling rate of 6-52 K / h.

[0015] Preferably, the high-temperature smelting process has a cooling rate of 6-10 K / h to cool to 923 K-823 K, and then a cooling rate of 45-52 K / h to cool to room temperature.

[0016] Preferably, the sealed reaction tube with a vacuum degree of not more than Pa is achieved by vacuum sealing treatment, specifically by using a vacuum pump to draw the vacuum degree of the reaction tube containing the raw materials to <10 -4 Pa, and then using a hydrogen-oxygen flame to vacuum seal, so that the raw materials do not react with oxygen in the air during the reaction.

[0017] Preferably, the grinding of the ingot in step (2) needs to be carried out in a vacuum environment, and the particle size of the powder is 200-300 mesh. Preferably, the ingot needs to be ground in a clean agate mortar in a glove box for 10 to 15 minutes.

[0018] Preferably, the spark plasma sintering process in step (2) has the following specific steps: the powder is heated to 450-500℃ at a heating rate of 50-90℃ / min, the pressure is adjusted to 40-50 MPa, and the temperature and pressure are maintained for 5-10 min, and then the powder is naturally cooled to room temperature under vacuum.

[0019] Preferably, the purity of the raw materials, i.e. K block, Bi particles and S particles, in step (1) is ≥99.99%.

[0020] The beneficial effects of the present application are as follows:

[0021] (1) The n-type K2Bi of the present application 8+x S 13 The thermoelectric material improves the electrical transport performance of the material by means of doping to improve the carrier concentration, greatly improves the power factor, and reduces the lattice thermal conductivity, thereby obtaining the n-type K2Bi 8+x S 13 The thermoelectric material has good thermoelectric performance.

[0022] (2) The n-type K2Bi of the present application 8+x S 13 The thermoelectric material can be prepared by various existing methods.

[0023] (3) The n-type K2Bi thermoelectric material of the present application is prepared by high-temperature smelting combined with a spark plasma sintering method 8+x S 13 The method allows the raw materials to react in a molten state to improve solute transport efficiency, and compared with the traditional solid-phase method, can obtain high-quality ingots in a shorter time, and then using the spark plasma sintering method can quickly prepare densified samples. The method can synthesize high-quality and high-purity n-type K2Bi 8+x S 13 thermoelectric material in large quantities. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is a powder X-ray diffraction pattern in Examples 1-5 of the present application;

[0025] Figure 2 is a carrier concentration graph of the thermoelectric material in Examples 1-5 of the present application with Bi content change;

[0026] Figure 3 is a conductivity graph of the thermoelectric material in Examples 1-5 of the present application with temperature change;

[0027] Figure 4 is a Seebeck coefficient graph of the thermoelectric material in Examples 1-5 of the present application with temperature change;

[0028] Figure 5 is a power factor graph of the thermoelectric material in Examples 1-5 of the present application with temperature change;

[0029] Figure 6 is a total thermal conductivity graph of the thermoelectric material in Examples 1-5 of the present application with temperature change;

[0030] Figure 7 is a lattice thermal conductivity graph of the thermoelectric material in Examples 1-5 of the present application with temperature change;

[0031] Figure 8Figures showing the temperature-dependent thermoelectric figure of merit of the thermoelectric materials in Examples 1-5 of the present application. DETAILED DESCRIPTION

[0032] In order to make the objects, technical solutions, and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are merely intended to explain the present application and are not intended to limit the present application. In addition, the technical features involved in the various embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0033] Example 1

[0034] A K2Bi8S 13 A method for preparing a thermoelectric material, comprising the following steps:

[0035] (1) In an argon glove box, K blocks (99.99%, National Pharmaceutical Group Chemical Reagents Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S=2:8:13, with a total mass of 10 g, and were loaded into a carbon-coated quartz tube.

[0036] (2) The quartz tube loaded with the raw materials was evacuated to Pa and was flame sealed.

[0037] (3) The sealed quartz tube was placed in a muffle furnace, and was heated to 1023 K at a rate of 40 h, and was cooled to 823 K at a rate of 20 h after being kept at 1023 K for 78 h, and was then cooled to room temperature at a rate of 10 h, to obtain a K2Bi8S 13 ingot.

[0038] (4) The ingot was ground into powder in a marquise mortar in the glove box for 10 min, and was loaded into a graphite mold.

[0039] (5) The uniform powder was densified by a spark plasma sintering technique under vacuum by applying a pressure of 40 MPa, specifically, the uniform powder was heated to 450°C at a heating rate of 70°C / min, the pressure was adjusted to 40 MPa, and the temperature and pressure were kept constant for 5 min, and then the sample was naturally cooled to room temperature under vacuum. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of >97% was obtained.

[0040] Example 2

[0041] A K2Bi 8.001 S 13 A method for preparing a thermoelectric material, comprising the following steps:

[0042] (1) In an argon glove box, K block (99.99%, National Pharmaceutical Group Chemical Reagent Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S = 2:8.001:13, and the total mass was 10 g, and then were loaded into a carbon-coated quartz tube.

[0043] (2) The quartz tube loaded with the raw materials was vacuumed to 1.0 × 10-3 Pa and flame sealed.

[0044] (3) The sealed quartz tube was placed in a muffle furnace, and was heated to 1023 K at a rate of 40 h, and was kept at 1023 K for 78 h, and then was cooled to 823 K at a rate of 20 h, and was cooled to room temperature at a rate of 10 h, to obtain K2BiS cast ingot. 8.001 13

[0045] (4) In the glove box, the cast ingot was ground into powder with a agate mortar for 10 min, and was loaded into a graphite mold.

[0046] (5) The uniform powder was densified by a spark plasma sintering technology under a pressure of 40 MPa in a vacuum environment, specifically, the uniform powder was heated to 450 ℃ at a heating rate of 70 ℃ / min, the pressure was adjusted to 40 MPa, and the temperature and pressure were kept constant for 5 min, and then the system was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of >97% was obtained.

[0047] Example 3

[0048] A method for preparing a K2BiS thermoelectric material, comprising the following steps: 8.002 13

[0049] (1) In an argon glove box, K block (99.99%, National Pharmaceutical Group Chemical Reagent Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S = 2:8.002:13, and the total mass was 10 g, and then were loaded into a carbon-coated quartz tube.

[0050] (2) The quartz tube loaded with the raw materials was vacuumed to 1.0 × 10-3 Pa and flame sealed.

[0051] (3) The sealed quartz tube was placed in a muffle furnace, and was heated to 1023 K at a rate of 40 h, and was kept at 1023 K for 78 h, and then was cooled to 823 K at a rate of 20 h, and was cooled to room temperature at a rate of 10 h, to obtain K2BiS cast ingot. 8.002 13 ​​​​​​​​

[0052] (4) The ingot was ground into powder in a marble mortar for 10 min in a glove box and loaded into a graphite die.

[0053] (5) The powder was densified by spark plasma sintering under a pressure of 40 MPa in a vacuum, specifically, the uniform powder was heated to 450°C at a heating rate of 70°C / min, the pressure was adjusted to 40 MPa, and the temperature and pressure were kept constant for 5 min, and then the sample was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of >97% was obtained.

[0054] Example 4

[0055] A K2Bi 8.003 S 13 A method for preparing a thermoelectric material, comprising the following steps:

[0056] (1) In an argon glove box, K blocks (99.99%, National Pharmaceutical Group Chemical Reagents Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S=2:8.003:13, and the total mass was 10 g, and then loaded into a carbon-coated quartz tube.

[0057] (2) The quartz tube containing the raw materials was evacuated to Pa and flame sealed.

[0058] (3) The sealed quartz tube was placed in a muffle furnace, and heated to 1023K at a rate of 40h, and then cooled to 823K at a rate of 20h, and then cooled to room temperature at a rate of 10h, to obtain a K2Bi 8.003 S 13 ingot.

[0059] (4) The ingot was ground into powder in a marble mortar for 10 min in a glove box and loaded into a graphite die.

[0060] (5) The powder was densified by spark plasma sintering under a pressure of 40 MPa in a vacuum, specifically, the uniform powder was heated to 450°C at a heating rate of 70°C / min, the pressure was adjusted to 40 MPa, and the temperature and pressure were kept constant for 5 min, and then the sample was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of >97% was obtained.

[0061] Example 5

[0062] A K2Bi 8.004 S 13 A method for preparing a thermoelectric material, comprising the following steps:

[0063] (1) In an argon glove box, K block (99.99%, National Pharmaceutical Group Chemical Reagent Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S = 2:8.004:13, and the total mass was 10 g, and then were loaded into a carbon-coated quartz tube.

[0064] (2) The quartz tube loaded with the raw materials was vacuumed to 1.33*10-3 Pa and flame sealed.

[0065] (3) The sealed quartz tube was placed in a muffle furnace, and was heated to 1023 K at a rate of 40 h, and was cooled to 823 K at a rate of 20 h after being kept at 1023 K for 78 h, and was cooled to room temperature at a rate of 10 h, to obtain K2Bi 8.004 S 13 ingot.

[0066] (4) The ingot was ground into powder in a marble mortar for 10 min in the glove box, and was loaded into a graphite mold.

[0067] (5) The powder was densified by a spark plasma sintering technology under a pressure of 40 MPa in a vacuum environment, specifically, the uniform powder was heated to 450 ℃ at a heating rate of 70 ℃ / min, the pressure was adjusted to 40 MPa, and the temperature and pressure were kept constant for 5 min, and then the system was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of >97% was obtained.

[0068] Example 6

[0069] A method for preparing a K2Bi 8.001 S 13 thermoelectric material, comprising the following steps:

[0070] (1) In an argon glove box, K block (99.99%, National Pharmaceutical Group Chemical Reagent Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S = 2:8.001:13, and the total mass was 10 g, and then were loaded into a carbon-coated quartz tube.

[0071] (2) The quartz tube loaded with the raw materials was vacuumed to 1.33*10-3 Pa and flame sealed.

[0072] (3) The sealed quartz tube was placed in a muffle furnace, and was heated to 1073 K at a rate of 18 K / h, and was cooled to 823 K at a rate of 8 K / h after being kept at 1073 K for 72 h, and was cooled to room temperature at a rate of 52 K / h, to obtain K2Bi 8.001 S 13 ingot.​​

[0073] (4) The ingot was ground into powder in a marble mortar for 10 min in a glove box and loaded into a graphite mold.

[0074] (5) The powder was densified by spark plasma sintering under a pressure of 50 MPa, specifically, the uniform powder was heated to 450 °C at a heating rate of 50 °C / min, the pressure was adjusted to 50 MPa, and the temperature and pressure were maintained for 5 min, and then the sample was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of > 97% was obtained.

[0075] Example 7

[0076] A K2Bi 8.001 S 13 A method for preparing a thermoelectric material, comprising the following steps:

[0077] (1) In an argon glove box, K blocks (99.99%, National Pharmaceutical Group Chemical Reagents Co., Ltd.), Bi particles (99.99%, Hebei Luohong Technology Co., Ltd.), and S particles (99.99%, Hebei Luohong Technology Co., Ltd.) were weighed according to the stoichiometric ratio K:Bi:S = 2:8.001:13, and the total mass was 10 g, and then loaded into a carbon-coated quartz tube.

[0078] (2) The quartz tube containing the raw materials was evacuated to Pa and flame sealed.

[0079] (3) The sealed quartz tube was placed in a muffle furnace and heated to 873 K at a heating rate of 11 K / h, and then cooled to 800 K at a cooling rate of 12 K / h, and then cooled to room temperature at a cooling rate of 45 K / h, to obtain a K2Bi 8.001 S 13 ingot.

[0080] (4) The ingot was ground into powder in a marble mortar for 10 min in a glove box and loaded into a graphite mold.

[0081] (5) The powder was densified by spark plasma sintering under a pressure of 45 MPa, specifically, the uniform powder was heated to 500 °C at a heating rate of 90 °C / min, the pressure was adjusted to 45 MPa, and the temperature and pressure were maintained for 10 min, and then the sample was naturally cooled to room temperature in a vacuum environment. A bulk material with a diameter of 12.7 mm, a thickness of 10 mm, and a relative density of > 97% was obtained.

[0082] The K2Bi 8+x S 13 thermoelectric material prepared in the above Examples 1-5 had the following results:

[0083] Figure 1 K2Bi8S 8+x S 13 The powder XRD pattern of the thermoelectric material. A small amount of K2Bi 8+x S 13 The compound powder was subjected to powder X-ray diffraction analysis. The X-ray diffraction peaks of the prepared sample were completely consistent with the standard card of K2Bi 13 8S, indicating that K2Bi 8+x S 13 The thermoelectric material was successfully prepared in Examples 1 to 5 of the present application.

[0084] Figure 2 K2Bi8S 8+x S 13 The relationship between the carrier concentration of the thermoelectric material and the Bi content. The sample after spark plasma sintering was cut and polished into a square piece of 6x6x1mm 3 , and the thermoelectric material prepared in Examples 1 to 5 was tested using a Hall electrical property test system (NYMS). As can be seen from Figure 2 , after doping Bi, the carrier concentration increased significantly, and with the increase of x, i.e. the increase of the doping amount of Bi, the carrier concentration showed an upward trend.

[0085] Figure 3 K2Bi8S 8+x S 13 The relationship between the electrical conductivity of the thermoelectric material and the temperature. The sample after spark plasma sintering was cut and polished into a rectangular cuboid of 10x3x3mm 3 , and the electrical conductivity was measured using a thermoelectric material test system CTA-3S of Beijing Kao Ruiou Technology Co., Ltd. As can be seen from Figure 3 , after doping Bi (Examples 2 to 5), the electrical conductivity was significantly higher than that without doping Bi (Example 1); and with the increase of x, i.e. the increase of the doping amount of Bi, the electrical conductivity first increased and then decreased, reaching a maximum at x=0.003, and the electrical conductivity at 300K was 133.71Scm -1 .

[0086] Figure 4 K2Bi8S 8+x S 13 The relationship between the Seebeck coefficient of the thermoelectric material and the temperature. The sample after spark plasma sintering was cut and polished into a rectangular cuboid of 10x3x3mm 3 , and the Seebeck coefficient was measured using a thermoelectric material test system CTA-3 of Beijing Kao Ruiou Technology Co., Ltd. As can be seen from Figure 4 , the Seebeck coefficient was negative at 300K-823K, proving that the K2Bi 8+x S 13 thermoelectric material was an n-type semiconductor.

[0087] Figure 5 K2Bi 8+x S 13 The relationship between the power factor and temperature of the thermoelectric material. The power factor (PF) is calculated by PF = σS 2 . It can be seen from Figure 5 that after doping Bi (Examples 2 to 5), the power factor is obviously higher than that without doping Bi (Example 1); with the increase of x, the power factor first increases and then decreases, and reaches the maximum at x = 0.003, PF = 3.08 at 823K .

[0088] Figure 6 K2Bi 8+x S 13 The relationship between the total thermal conductivity and temperature of the thermoelectric material. The sample after spark plasma sintering is cut and polished into a square piece of 6x6x1mm 3 , the thermal diffusivity D is tested by using the laser flash thermal conductivity instrument LFA467 of Germany Nanjing Company, and the total thermal conductivity (κ tot ) is calculated by κ tot = C p Dρ, the density ρ is tested by the Archimedes drainage method, and the specific heat C p is calculated by the Dulong-Petit formula. It can be seen from Figure 6 that with the increase of x, the total thermal conductivity first increases and then decreases, and reaches the minimum at x = 0.004, κ tot = 0.45Wm -1 K -1 at 823K

[0089] Figure 7 K2Bi 8+x S 13 The relationship between the lattice thermal conductivity and temperature of the thermoelectric material. The lattice thermal conductivity (κ lat ) is obtained by κ la = κ tot – LσT, L is the Lorenz constant, and T is the absolute temperature. It can be seen from Figure 7 that with the increase of x, the lattice thermal conductivity first increases and then decreases, and reaches the minimum at x = 0.004, κ tot = 0.37Wm -1 K -1 at 823K

[0090] Figure 8 K2Bi 8+x S 13 The relationship between the thermoelectric figure of merit and temperature of the thermoelectric material. The thermoelectric figure of merit (ZT) is obtained by ZT = S 2 σT / κ tot .Figure 8 It can be seen that, with the increase of x, the thermoelectric merit value first rises and then falls, and reaches the maximum at x=0.003, ZT=0.53 at 823K.

[0091] In summary, compared with example 1, the n-type K2Bi 8+x S 13 The thermoelectric material is regulated by means of doping to control the carrier concentration, improve the electrical transport performance of the material, greatly improve the power factor, and reduce the lattice thermal conductivity, and thus the n-type K2Bi 8+x S 13 The thermoelectric material has good thermoelectric performance. The K2Bi 8+x S 13 The thermoelectric material has good electrical conductivity and Seebeck coefficient, and low lattice thermal conductivity, and has good application prospect.

[0092] Those skilled in the art will readily understand that the above description is only a preferred embodiment of the present application, and is not intended to limit the present application, and any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application.

[0093] The part of the present application specification not described in detail belongs to the known technology in the art, and the above examples are only provided for the purpose of describing the present application, and are not intended to limit the scope of the present application. The scope of the present application is defined by the appended claims. Any equivalent replacement and modification made without departing from the spirit and principle of the present application shall be included in the scope of the present application.

Claims

1. A thermoelectric material, characterized by, The thermoelectric material has a chemical formula of K2Bi 8+x S 13 The thermoelectric material is n-type, wherein 0 < x < 0.

004.

2. The thermoelectric material of claim 1, wherein, x is 0.001, 0.002, 0.003 or 0.

004.

3. The method of producing a thermoelectric material according to claim 1 or 2, characterized by, The method comprises the following steps: (1) high-temperature smelting step: in a vacuum environment, high-temperature smelting treatment is performed on raw materials weighed according to stoichiometric ratio to obtain K2Bi 8+x S 13 ingot; the temperature of the high-temperature smelting treatment is 873~1073K, and the holding time is 72~82h; (2) densification step: the K2Bi 8+x S 13 ingot is ground into powder, and the powder is subjected to spark plasma sintering treatment for 10-20 min under vacuum to obtain K2Bi 8+x S 13 thermoelectric material bulk; wherein the spark plasma sintering treatment is carried out under a pressure of 40-50 MPa.

4. The method of producing a thermoelectric material according to claim 3, wherein: The high-temperature melting treatment is performed at a vacuum degree of not more than 10"2Pa in a sealed reaction tube of Pa.

5. The method of producing a thermoelectric material according to claim 4, wherein The reaction tube is a quartz tube plated with a carbon film, and the thickness of the carbon film plated on the quartz tube is 50-200 nm.

6. The method of producing a thermoelectric material according to claim 3, wherein: The temperature rising rate of the high-temperature smelting is 11-18 K / h, and the temperature falling rate is 6-52 K / h.

7. The method of claim 6, wherein: The temperature falling rate of the high-temperature smelting is specifically a temperature falling rate of 6-10 K / h to cool to 923 K-823 K, and then a temperature falling rate of 45-52 K / h to cool to room temperature.

8. The method of producing a thermoelectric material according to claim 4, wherein The vacuum degree is not more than 10 The sealed reaction tube of Pa is achieved by vacuum sealing treatment, specifically, the reaction tube containing raw materials is vacuumed by vacuum pump to <10 -4 Pa, and then vacuum sealed by hydrogen oxygen flame.

9. The method of producing a thermoelectric material according to claim 3, wherein The grinding of the cast ingot in step (2) needs to be performed in a vacuum environment, and the particle size of the powder is 200-300 mesh.

10. The method of producing a thermoelectric material according to claim 3, wherein The specific step of the discharge plasma sintering treatment in step (2) is: the powder is heated to 450-500 DEG C through a temperature rising rate of 50-90 DEG C / min, the pressure is adjusted to 40-50 MPa, the temperature and pressure are maintained for 5-10 min, and then the powder is naturally cooled to room temperature in a vacuum environment.

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