A P-type KCu 7(1-x) Preparation method of S4 thermoelectric material

Abstract

The present invention discloses a P-type KCu 7(1‑x) The preparation method of S4 thermoelectric material specifically comprises the following steps: S1, weighing: weighing and uniformly mixing high-purity K blocks, Cu particles and S particles according to the molar ratio of K:Cu:S=1:7(1-x):4, ​​wherein the value of x is 0, 0.01, 0.02, 0.03, 0.035, 0.04 or 0.05; S2, vacuum packaging: placing the raw materials weighed in step S1 into a quartz tube with a carbon film coated on the inner wall and vacuum sealing to obtain a vacuum-sealed quartz tube; S3, smelting: placing the quartz tube sealed in step S2 into a muffle furnace for smelting to obtain a smelted ingot; S4, grinding: grinding the ingot in step S3 in a glove box with an agate mortar to obtain a uniform powder; S5, spark plasma sintering: placing the uniform powder in step S4 into a graphite mold and pressing it into a block by spark plasma sintering to obtain a high-density block, i.e., KCu 7(1‑x) S4 thermoelectric material.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance thermoelectric material preparation, and in particular to a P-type KCu 7(1-x) S4 preparation method of thermoelectric material. Background Art

[0002] With the rapid development of global industry, the demand for electricity generated by burning fossil fuels has increased significantly. However, during the fossil fuel combustion process, over 50% of the energy is lost to the surrounding environment as waste heat, and large amounts of exhaust gas are emitted, which can easily lead to a series of environmental problems such as global warming and rising sea levels. To resolve the energy crisis, the search for alternative clean energy sources and the construction of a sustainable society have become the development themes of countries around the world in the 21st century.

[0003] Thermoelectric energy conversion technology enables direct conversion of heat and electricity, effectively recovering waste heat without generating pollution. Thermoelectric devices offer advantages such as solid-state design, compact size, fast response, and the absence of moving parts and hazardous working fluids. They hold broad application prospects in thermoelectric power generation and thermoelectric cooling.

[0004] Copper-based thermoelectric materials have attracted extensive attention due to their excellent thermoelectric performance, cost-effectiveness, and environmental friendliness. 2-x M (M=Te, Se, S) has intrinsically low κ due to its liquid-like ions lat However, the directional migration of Cu ions at high temperatures leads to a decrease in thermoelectric performance and stability, limiting the long-term stability of the device. However, with the widespread use of thermoelectric devices, extremely high requirements are placed on the preparation method, requiring a simple and large-scale preparation method. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a P-type KCu 7(1-x) The preparation method of S4 thermoelectric material is simple to operate, has a high success rate, and produces pure products. It can be used to mass-produce high-performance P-type KCu 7(1-x) S4 thermoelectric material, the prepared KCu 7(1-x) S4 thermoelectric material has high thermoelectric figure of merit and good application prospects.

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

[0007] A P-type KCu 7(1-x) The preparation method of S4 thermoelectric material specifically comprises the following steps:

[0008] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles in a molar ratio of K:Cu:S=1:7(1-x):4, ​​where x is 0, 0.01, 0.02, 0.03, 0.035, 0.04, or 0.05.

[0009] S2, vacuum packaging: placing the raw materials weighed in step S1 into a quartz tube with a carbon film coated inner wall and vacuum sealing to obtain a vacuum sealed quartz tube;

[0010] S3, smelting: placing the quartz tube sealed in step S2 into a muffle furnace for smelting to obtain a smelted ingot;

[0011] S4, grinding: grinding the ingot in step S3 in a glove box using an agate mortar to obtain a uniform powder;

[0012] S5, spark plasma sintering: the uniform powder in step S4 is placed in a graphite mold and pressed into blocks by spark plasma sintering to obtain a high-density block, namely KCu 7(1-x) S4 thermoelectric material.

[0013] Preferably, in step S1, the purity of the K blocks, Cu particles and S particles is ≥99.99%.

[0014] Preferably, the vacuum sealing process in step S2 is: the vacuum degree of the quartz tube containing the raw materials is pumped to <10 -3 Pa, and then adopt hydrogen-oxygen flame to vacuum seal to prevent the raw materials from reacting with oxygen in the air during the reaction process.

[0015] Preferably, the smelting process in step S3 is: slowly heating the quartz tube containing the raw materials to 800°C through a muffle furnace at a heating rate of 0.5-0.7°C / min, and keeping the temperature constant for 1440 minutes to ensure that the raw materials are fully reacted in a molten state, and then cooling to 400°C at a rate of 1.2-1.4°C / min, keeping the temperature constant for 1440 minutes, and then cooling with the furnace.

[0016] Preferably, the process of spark plasma sintering and pressing into blocks in step S5 is: heating the uniform powder to 500°C at a heating rate of 70-80°C / min, adjusting the pressure to 40 MPa, maintaining constant temperature and pressure for 5 minutes, and then naturally cooling to room temperature under a vacuum environment.

[0017] Preferably, the relative sample density ρ / ρ0 of the high-density block in step S5 is ≥95%, wherein ρ is the sample density and ρ0 is the theoretical density of the material.

[0018] Preferably, the KCu in step S5 7(1-x)The lattice thermal conductivity of S4 thermoelectric material at 823K is 0.41~0.49Wm -1 K -1 .

[0019] Preferably, the KCu in step S5 7(1-x) The power factor of S4 thermoelectric material at 823K is 2.05~5.05μWcm -1 K -2 .

[0020] Preferably, the KCu in step S5 7(1-x) The thermoelectric figure of merit of S4 thermoelectric material at 823K is 0.39~0.8.

[0021] After adopting the above technical solution, the present invention has the following advantages compared with the background technology: the present invention adopts high temperature smelting method to prepare high performance KCu 7(1-x) S4 thermoelectric material, the process is simple, the preparation product is stable, by introducing Cu vacancies to adjust KCu 7(1-x) The hole concentration of S4 and the final KCu 7(1-x) The S4 sample has a single phase structure, high density, good crystallinity, and low lattice thermal conductivity. On the basis of the original low lattice thermal conductivity, a higher thermoelectric figure of merit is achieved by optimizing the carrier concentration. This method is simple to operate, time-saving, and suitable for the preparation of various system materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 KCu in Examples 1-7 of the present invention 7(1-x) Powder X-ray diffraction pattern of S4;

[0023] Figure 2 KCu in Examples 1-7 of the present invention 7(1-x) Carrier concentration diagram of S4 thermoelectric material as the Cu vacancy content changes;

[0024] Figure 3 KCu in Examples 1-7 of the present invention 7(1-x) S4 conductivity diagram of thermoelectric material as it changes with temperature;

[0025] Figure 4 KCu in Examples 1-7 of the present invention 7(1-x) S4 Seebeck coefficient diagram of thermoelectric materials as they change with temperature;

[0026] Figure 5 KCu in Examples 1-7 of the present invention 7(1-x) S4: Power factor diagram of thermoelectric material changing with temperature;

[0027] Figure 6 KCu in Examples 1-7 of the present invention 7(1-x)S4 Total thermal conductivity diagram of thermoelectric material as a function of temperature;

[0028] Figure 7 KCu in Examples 1-7 of the present invention 7(1-x) S4 lattice thermal conductivity diagram of thermoelectric materials as a function of temperature;

[0029] Figure 8 KCu in Examples 1-7 of the present invention 7(1-x) Thermoelectric figure of merit diagram of S4 thermoelectric material as it changes with temperature. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] See also Figures 1 to 8 .

[0032] Prepare raw materials K blocks, Cu pellets, and S pellets. The purity of K blocks is 99.99% (Sigma-Aldrich Trading Co., Ltd.), the purity of Cu pellets is 99.99% (Hebei Luohong Technology Co., Ltd.), and the purity of S pellets is 99.99% (Hebei Luohong Technology Co., Ltd.).

[0033] Example 1

[0034] A method for preparing a KCu7S4 thermoelectric material comprises the following steps:

[0035] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles in a molar ratio of K:Cu:S=1:7:4; the purity of K blocks, Cu particles, and S particles should be ≥99.99%.

[0036] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0037] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0038] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0039] S5. Spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block using spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The constant temperature and pressure were maintained for 5 minutes, and then naturally cooled to room temperature under a vacuum environment to obtain a high-density block, i.e., the KCu7S4 thermoelectric material.

[0040] Example 2

[0041] A KCu 6.93 The preparation method of S4 thermoelectric material comprises the following steps:

[0042] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.93:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0043] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0044] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0045] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0046] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.93 S4 thermoelectric material.

[0047] Example 3

[0048] A KCu 6.86 The preparation method of S4 thermoelectric material comprises the following steps:

[0049] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.86:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0050] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0051] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0052] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0053] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.86 S4 thermoelectric material.

[0054] Example 4

[0055] A KCu 6.79 The preparation method of S4 thermoelectric material comprises the following steps:

[0056] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.79:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0057] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0058] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0059] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0060] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.79 S4 thermoelectric material.

[0061] Example 5

[0062] A KCu 6.755 The preparation method of S4 thermoelectric material comprises the following steps:

[0063] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.755:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0064] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0065] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0066] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0067] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.755 S4 thermoelectric material.

[0068] Example 6

[0069] A KCu 6.72 The preparation method of S4 thermoelectric material comprises the following steps:

[0070] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.72:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0071] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0072] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0073] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0074] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.72 S4 thermoelectric material.

[0075] Example 7

[0076] A KCu 6.65 The preparation method of S4 thermoelectric material comprises the following steps:

[0077] S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles according to the molar ratio of K:Cu:S=1:6.65:4; the purity of K blocks, Cu particles, and S particles is ≥99.99%;

[0078] S2. Vacuum packaging: Place the raw materials weighed in step S1 into a quartz tube with a diameter of 13 mm and coated with a carbon film, and use a vacuum pump to evacuate the tube to a vacuum degree of <10 -3 Pa;

[0079] S3, smelting: placing the sealed quartz tube in step S2 into a muffle furnace and slowly heating the quartz tube containing the raw materials to 800° C. at a heating rate of 0.5° C. / min, and maintaining the temperature for 1440 min to ensure that the raw materials are fully reacted in a molten state, then cooling the temperature to 400° C. at a rate of 1.2° C. / min, maintaining the temperature for 1440 min, and then cooling with the furnace to obtain a smelted ingot;

[0080] S4, grinding: placing the ingot in step S3 in a glove box and manually grinding it with an agate mortar for 30 minutes to obtain a powder with uniform particles;

[0081] S5, spark plasma sintering (SPS): The uniform powder in step S4 was placed in a graphite mold with a diameter of 12.7 mm and pressed into a block by spark plasma sintering. The uniform powder was heated to 500°C at a heating rate of 70°C / min, and the pressure was adjusted to 40 MPa. The temperature and pressure were maintained at constant temperature and pressure for 5 minutes, and then naturally cooled to room temperature under vacuum to obtain a high-density block, namely KCu 6.65 S4 thermoelectric material.

[0082] The measured density, theoretical density and relative density of the thermoelectric materials prepared in Examples 1-7 are shown in Table 1.

[0083] Table 1 Measured density, theoretical density and relative density of thermoelectric materials prepared in Examples 1-7

[0084]

[0085] Performance testing:

[0086] (1) First, weigh 0.5g of KCu 7(1-x) The S4 compound (thermoelectric material prepared in Example 1-7) was then ground into a powder sample using an agate mortar and subjected to powder X-ray diffraction analysis. The X-ray diffraction peaks of the prepared sample were completely consistent with those of the KCu7S4 standard card, as shown in FIG. Figure 1 shown.

[0087] (2) The sintered samples were cut and polished into 1 mm thick discs, and the carrier concentration (n) of the thermoelectric materials prepared in Examples 1-7 was measured using a Hall effect test system (NYMS). H ), it can be seen from the test results that with the increase of Cu vacancy concentration, the carrier concentration shows an upward trend, such as Figure 2 shown.

[0088] (3) The electrical properties of the thermoelectric materials prepared in Examples 1-7 were measured using the thermoelectric material testing system CTA-3S of Beijing Coreo Technology Co., Ltd. The relationship between the electrical conductivity (σ) and the Seebeck coefficient (S) as a function of temperature is shown in the following figure: Figure 3 、 Figure 4 As shown. Power factor (PF) is given by σS 2 The relationship between power factor and temperature is calculated as follows: Figure 5 As shown, KCu 6.755 The power factor of S4 at 823K is 5.05μWcm -1 K -2 .

[0089] (4) The thermal diffusion coefficient D of the thermoelectric materials prepared in Examples 1-7 was tested using a laser flash thermal conductivity meter LFA467 from NETZSCH, Germany. The total thermal conductivity was measured by κ tot =C p Dρ is calculated, density ρ is obtained by Archimedes drainage method, specific heat C p It is calculated by the Dulong-Petit formula. The relationship between the total thermal conductivity and temperature is as follows: Figure 6 Lattice thermal conductivity (κ lat ) is derived from the total thermal conductivity (κ tot )-electronic thermal conductivity (κ ele ) is calculated, κ ele =LσT, L is the Lorentz constant, T is the absolute temperature. The relationship between lattice thermal conductivity and temperature is as follows Figure 7 As shown, KCu7S4 obtained a lower lattice thermal conductivity of 0.41 Wm at 823 K. -1 K -1 .

[0090] (5) Thermoelectric figure of merit ZT = S 2 σT / κ tot , the relationship with temperature is as follows Figure 8 As shown, KCu 6.755 The thermoelectric figure of merit (zT) of S4 obtained at 823K is 0.8.

[0091] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A P-type KCu 7(1-x) The preparation method of S4 thermoelectric material is characterized in that: The specific steps include: S1. Weighing: Weigh and mix high-purity K blocks, Cu particles, and S particles in a molar ratio of K:Cu:S=1:7(1-x):4, ​​where x is 0, 0.01, 0.02, 0.03, 0.035, 0.04, or 0.

05. S2, vacuum packaging: placing the raw materials weighed in step S1 into a quartz tube with a carbon film coated inner wall and vacuum sealing to obtain a vacuum sealed quartz tube; S3, smelting: placing the quartz tube sealed in step S2 into a muffle furnace for smelting to obtain a smelted ingot; S4, grinding: grinding the ingot in step S3 in a glove box using an agate mortar to obtain a uniform powder; S5, spark plasma sintering: the uniform powder in step S4 is placed in a graphite mold and pressed into blocks by spark plasma sintering to obtain a high-density block, namely KCu 7(1-x) S4 thermoelectric material.

2. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized by: In step S1, the purity of the K blocks, Cu particles and S particles is ≥99.99%.

3. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized in that: The vacuum sealing process in step S2 is as follows: the vacuum degree of the quartz tube containing the raw materials is pumped to <10 -3 Pa, and then adopt hydrogen-oxygen flame to vacuum seal to prevent the raw materials from reacting with oxygen in the air during the reaction process.

4. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized in that: The smelting process in step S3 is as follows: slowly heating the quartz tube containing the raw materials to 800°C through a muffle furnace at a heating rate of 0.5-0.7°C / min, and keeping the temperature constant for 1440 minutes to ensure that the raw materials are fully reacted in a molten state, and then cooling to 400°C at a rate of 1.2-1.4°C / min, keeping the temperature constant for 1440 minutes, and then cooling with the furnace.

5. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized in that: The process of spark plasma sintering and pressing into blocks in step S5 is as follows: heating the uniform powder to 500°C at a heating rate of 70-80°C / min, adjusting the pressure to 40 MPa, maintaining constant temperature and pressure for 5 minutes, and then naturally cooling to room temperature under vacuum.

6. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized by: The relative sample density of the high-density block in step S5 ρ / ρ 0≥95%, of which, ρ is the sample density, ρ 0 is the theoretical density of the material.

7. A P-type KCu as claimed in claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized by: The KCu 7(1-x) The lattice thermal conductivity of S4 thermoelectric material at 823K is 0.41~0.49 Wm -1 K -1 .

8. The P-type KCu according to claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized by: The KCu 7(1-x) The power factor of the S4 thermoelectric material at 823 K is 2.05~5.05 μWcm -1 K -2 .

9. The P-type KCu according to claim 1 7(1-x) The preparation method of S4 thermoelectric material is characterized by: The KCu 7(1-x) The thermoelectric figure of merit of S4 thermoelectric material at 823 K is 0.39~0.8.

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