A p-type silver bismuth sulfide-based polycrystalline bulk thermoelectric material, a preparation method and applications thereof

Abstract

The application provides a P-type silver-bismuth-sulfur-based polycrystalline block thermoelectric material, a preparation method and application thereof. 3‑x S 5.08 The chemical general formula of the P-type silver-bismuth-sulfur-based polycrystalline block thermoelectric material is AgBi 0.3 <= x <= 0.6. The P-type silver-bismuth-sulfur-based polycrystalline block thermoelectric material with reduced molar ratio of bismuth elements is synthesized by using raw materials with a purity of 99.9999% and a high-temperature melting method, and a P-type silver-bismuth-sulfur-based ingot with uneven density and many pores is obtained. Then, the ingot is fully ground in an agate mortar to obtain a powder with uniform size, and the powder is poured into a graphite mold and subjected to discharge plasma sintering to obtain the P-type silver-bismuth-sulfur-based polycrystalline block thermoelectric material with uniform density. The P-type silver-bismuth-sulfur-based polycrystalline block thermoelectric material is prepared for the first time, the material is easy to obtain, the preparation process is simple, and the material has potential to become a high-performance medium-low-temperature thermoelectric material.

Description

Technical Field

[0001] This invention relates to a P-type polycrystalline bulk thermoelectric material, specifically a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material, its preparation method, and its applications. Background Technology

[0002] Thermoelectric materials convert heat energy into electrical energy using temperature differences. Like hydropower and wind power, they are a sustainable and environmentally friendly green energy source. Furthermore, thermoelectric materials can recycle waste heat generated by machinery such as automobiles, reducing energy consumption. Currently, lead and tellurium compounds are recognized as highly efficient thermoelectric materials. However, their reserves are extremely scarce, their production costs are high, and lead is toxic. Therefore, finding abundant, highly efficient, and green alternatives is one of the urgent problems that needs to be solved.

[0003] The elements required for the synthesis of silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials are all abundant, non-toxic, and pollution-free. Intrinsic silver-bismuth-sulfur-based thermoelectric materials possess low lattice thermal conductivity, making them promising high-performance thermoelectric materials with wide applications in aerospace, thermoelectric cooling, and sensors and temperature controllers in microelectronic devices. However, currently reported silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials are all N-type; therefore, developing P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials will be beneficial for further development of this field. Summary of the Invention

[0004] One of the objectives of this invention is to provide a P-type silver bismuth sulfide-based polycrystalline bulk thermoelectric material to solve the problems in the practical application of existing silver bismuth sulfide-based polycrystalline bulk thermoelectric materials.

[0005] The second objective of this invention is to provide a method for preparing a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

[0006] The third objective of this invention is to provide the application of the aforementioned P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material in thermoelectric energy conversion.

[0007] One of the objectives of this invention is achieved as follows:

[0008] A p-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material with the general chemical formula AgBi 3-x S 5.08 Where 0.3≤x≤0.6. The P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is prepared by high-temperature melting and discharge plasma sintering technology.

[0009] This invention uses elemental silver, bismuth, and sulfur, all with a purity of 99.9999%, and controls the molar ratio of each element during the preparation of the silver-bismuth-sulfur-based polycrystalline bulk material to achieve a molar ratio of Ag∶Bi∶S=1∶3-x∶5.08, where 0.3≤x≤0.6. A higher sulfur content compensates for losses caused by sulfur adhering to the quartz tube wall after cooling due to its low saturated vapor pressure during high-temperature melting. In the N-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material, bismuth provides a large number of electrons; each bismuth atom can provide three electrons. Reducing the molar ratio of bismuth in the material effectively lowers the electron concentration, promoting the transformation of the material from N-type to P-type.

[0010] The P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is a uniformly dense column with a diameter of 12 mm and a height of 10 mm; its density is 6.4–6.6 mg / m³. 3 Its Seebeck coefficient is 5000–20000 μVK. -1 .

[0011] The second objective of this invention is achieved as follows:

[0012] A method for preparing a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material includes the following steps:

[0013] (a) P-type silver-bismuth-sulfur-based ingots were prepared by a high-temperature melting method; specifically: according to the general chemical formula AgBi 3-x S 5.08 In the formula (0.3≤x≤0.6), weigh out elemental silver, bismuth, and sulfur, each with a purity of 99.9999%. Place the weighed substances into a quartz tube, evacuate the quartz tube, seal it, and then place the sealed quartz tube into a muffle furnace for a high-temperature melting reaction. The chemical formula is AgBi. 3-x S 5.08 The subscript 5.08 for S is used to compensate for the loss of S during the high-temperature melting process.

[0014] (b) The non-uniform density P-type silver bismuth sulfur-based ingot prepared in step (a) is ground into uniformly sized powder in an agate mortar. The powder is placed into a graphite mold, pre-pressed with a cold press, and then subjected to discharge plasma sintering to obtain a dense P-type silver bismuth sulfur-based polycrystalline bulk thermoelectric material.

[0015] In step (a), the weighed substance is placed in a quartz tube with a diameter of 13 mm and a height of 170 mm, under a vacuum degree higher than 4*10. -3 After Pa, the tube is sealed.

[0016] The high-temperature melting method can employ reaction temperatures and reaction times known to those skilled in the art, wherein the reaction temperature is 900–1100 degrees Celsius and the reaction time is 5–10 hours.

[0017] In step (b), the powder is ground by hand in an agate mortar for 10 to 30 minutes. After that, the ground powder is placed into a graphite mold with an inner diameter of 12 mm for pre-pressing.

[0018] In step (b), the pressure at both ends of the graphite mold during the discharge plasma sintering process is 50 MPa, the reaction temperature is 450-500 degrees Celsius, preferably 500 degrees Celsius, and the reaction time is 5-7 minutes, preferably 5 minutes.

[0019] The third objective of this invention is achieved as follows:

[0020] The aforementioned P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials are used in thermoelectric energy conversion.

[0021] This invention designs a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material with a reduced molar ratio of bismuth. Raw materials with a purity of 99.9999% are weighed according to a specified ratio and synthesized using a high-temperature melting method to obtain a P-type silver-bismuth-sulfur-based ingot with uneven density and numerous pores. This ingot is then thoroughly ground into a uniformly sized powder in an agate mortar. The powder is poured into a graphite mold and sintered using discharge plasma to obtain a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material with uniform density.

[0022] This invention is the first to prepare a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material. The material is easy to obtain and the preparation process is simple, and it has the potential to become a high-performance medium- and low-temperature thermoelectric material. Attached Figure Description

[0023] Figure 1 These are the XRD spectra of the samples prepared in Examples 1-6 and the silver bismuth sulfide standard samples.

[0024] Figure 2 These are conductivity diagrams of the samples prepared in Examples 1 to 6.

[0025] Figure 3 This is a Seebeck coefficient diagram of the samples prepared in Examples 1 to 6.

[0026] Figure 4 The thermoelectric figure of merit (ZT) diagrams of the samples prepared in Examples 3-6 are shown.

[0027] Figure 5 This is a Seebeck coefficient diagram of the sample prepared in Comparative Example 1. Detailed Implementation

[0028] The present invention will be further described below with reference to the embodiments. The embodiments described below are for illustration only and do not limit the scope of protection of the present invention in any way.

[0029] The processes and methods not described in detail in the following embodiments are conventional methods known in the art, and the pharmaceuticals used in the embodiments are commercially available or prepared by methods well known to those skilled in the art. The following embodiments all achieve the objectives of the present invention.

[0030] Example 1

[0031] 1.29g of silver, 7.27g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.9 S 5.08 (Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained. 2.9 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0032] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-3 As shown. From Figure 1 It can be seen that the prepared AgBi 2.9 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, with no obvious impurity peaks. Figure 3 AgBi obtained from 2.9 S 5.08 The Seebeck coefficient of silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials is negative, compared to... Figure 5 The Seebeck coefficient of the intrinsic silver-bismuth-sulfur-based material increases by 1.2 times, but it is still an N-type conductive material. This proves that reducing the molar ratio of bismuth in the material can effectively reduce the electron carrier concentration and promote the transformation of the silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material from N-type to P-type conductivity.

[0033] Example 2

[0034] 1.29g of silver, 7.02g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.8 S 5.08(Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained. 2.8 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0035] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-3 As shown. From Figure 1 It can be seen that the prepared AgBi 2.8 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, showing no obvious impurity peaks. Figure 2 , Figure 3 It can be seen that the obtained AgBi 2.8 S 5.08 Silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials remain N-type conductive materials, compared to AgBi. 2.9 S 5.08 The electrical conductivity of silver bismuth sulfide-based materials is significantly reduced, the electron carrier concentration is decreased, and the Seebeck value is smaller but still negative. This proves that reducing the molar ratio of bismuth in the material can effectively reduce the electron carrier concentration and promote the transformation of silver bismuth sulfide-based polycrystalline bulk thermoelectric materials from N-type conductivity to P-type conductivity.

[0036] Example 3

[0037] 1.29g of silver, 6.77g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.7 S 5.08 (Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained. 2.7 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0038] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-4 As shown. From Figure 1 It can be seen that the prepared AgBi 2.7 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, showing no obvious impurity peaks. Figure 2 , Figure 3 It can be seen that the obtained AgBi 2.7 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric materials convert to P-type conductivity in the temperature range of room temperature to 50 degrees Celsius, exhibiting very low conductivity and a Seebeck coefficient that becomes positive, reaching 5000 μV / K. -1 Thermoelectric figure of merit ZT, such as Figure 4 As shown, this demonstrates the successful preparation of P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

[0039] Example 4

[0040] 1.29g of silver, 6.52g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.6 S 5.08 (Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained.2.6 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0041] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-4 As shown. From Figure 1 It can be seen that the prepared AgBi 2.6 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, showing no obvious impurity peaks. Figure 2 , Figure 3 It can be seen that the obtained AgBi 2.6 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric materials convert to P-type conductivity in the temperature range of room temperature to 100 degrees Celsius, and the temperature range is further expanded, with a thermoelectric figure of merit ZT as shown. Figure 4 As shown, this demonstrates the successful preparation of a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

[0042] Example 5

[0043] 1.29g of silver, 6.27g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.5 S 5.08 (Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained. 2.5 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0044] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-4 As shown. From Figure 1 It can be seen that the prepared AgBi 2.5 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, showing no obvious impurity peaks. Figure 2 , Figure 3 It can be seen that the obtained AgBi 2.5S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material converts to P-type conductivity in the temperature range of room temperature to 100°C, with a slight increase in material conductivity and a Seebeck coefficient reaching 20000 μVK. -1 Thermoelectric figure of merit ZT, such as Figure 4 As shown, this demonstrates the successful preparation of a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

[0045] Example 6

[0046] 1.29g of silver, 6.02g of bismuth, and 1.95g of sulfur, all with a purity of 99.9999% (molar ratio according to AgBi), were added. 2.4 S 5.08 (Weighing) After weighing, place it into a quartz tube with a diameter of 13 mm and a height of 170 mm, and place it under a vacuum of less than 4*10. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature for 15 hours, then increased to 450°C and held for 2 hours; 3 hours later, increased to 600°C and held for 2 hours; 8 hours later, increased to 1000°C and reacted for 5 hours; 2 hours later, decreased to 600°C and held for 48 hours; then cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes. The powder was then loaded into a graphite mold, pre-pressed using a cold press, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. After natural cooling to room temperature, AgBi was obtained. 2.4 S 5.08 Silver-bismuth-sulfur based polycrystalline bulk thermoelectric material.

[0047] The prepared material was subjected to XRD and thermoelectric property tests, and the results are as follows: Figures 1-4 As shown. From Figure 1 It can be seen that the prepared AgBi 2.4 S 5.08 The silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is consistent with PDF standard card 42-0539, showing no obvious impurity peaks. Figure 2 , Figure 3 It can be seen that the obtained AgBi 2.4 S 5.08 Silver-bismuth-sulfur-based polycrystalline bulk thermoelectric materials convert to P-type conductivity in the temperature range of room temperature to 75 degrees Celsius, the temperature range narrows, and the Seebeck coefficient of the material drops to 9800 μVK. -1 Thermoelectric figure of merit ZT, such as Figure 4 As shown, this demonstrates the successful preparation of a P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

[0048] Comparative Example 1

[0049] 1.29g of silver, 7.52g of bismuth, and 1.92g of sulfur (molar ratio based on AgBi3S5) with a purity of 99.9999% were weighed and placed into a quartz tube with a diameter of 13mm and a height of 170mm. The mixture was then placed under a vacuum of less than 4*10⁻⁶. -3 After Pa, the tube was sealed. The quartz tube was placed in a muffle furnace for high-temperature melting and reaction. The reaction temperature and time were as follows: room temperature was increased to 450°C after 15 hours and held for 2 hours; 3 hours later, it was increased to 600°C and held for 2 hours; 8 hours later, it was increased to 1000°C and reacted for 5 hours; 2 hours later, it was reduced to 600°C and held for 48 hours; then it was cooled to room temperature. The silver-bismuth-sulfur-based ingot prepared by the high-temperature melting method was stably ground in an agate mortar for 20 minutes, placed in a graphite mold, pre-pressed, and then subjected to discharge plasma sintering. The pressure at both ends of the graphite mold was 50 MPa, the reaction temperature was 500°C, and the reaction time was 5 minutes. Afterward, it was naturally cooled to room temperature to obtain the AgBi3S5 silver-bismuth-sulfur matrix.

[0050] The Seebeck coefficient of the prepared AgBi3S5 silver bismuth sulfur matrix was tested, and the results are shown in the figure. Figure 5 .from Figure 5 It can be seen that the Seebeck coefficient of the prepared AgBi3S5 silver bismuth sulfur matrix is ​​-185 to -215 μVK at room temperature to 100 degrees Celsius. -1 It is an N-type conductive material.

Claims

1. A P-type silver bismuth chalcogenide based polycrystalline bulk thermoelectric material, characterized by, The chemical formula is AgBi 3-x S 5.08 wherein 0.3≤ x ≤0.

6.

2. The P-type silver bismuth chalcogenide based polycrystalline bulk thermoelectric material of claim 1, wherein, The P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material is prepared by high-temperature melting and discharge plasma sintering.

3. The P-type silver bismuth chalcogenide based polycrystalline bulk thermoelectric material of claim 1, wherein, The P-type silver bismuth sulfide-based polycrystalline bulk thermoelectric material has a Seebeck coefficient of 5000-20000 μVK -1 .

4. The P-type silver bismuth chalcogenide based polycrystalline bulk thermoelectric material of claim 1, wherein, The P-type silver bismuth sulfide-based polycrystalline bulk thermoelectric material is a uniform density column with a diameter of 12 mm and a height of 10 mm, and the density is 6.4-6.6 mg / m 3 .

5. A method of making a P-type silver bismuth chalcogenide based polycrystalline bulk thermoelectric material, comprising The following steps are: (a) A silver bismuth sulfur-based ingot is prepared by high-temperature melting method; specifically, silver, bismuth, and sulfur elements with a purity of 99.9999% are weighed according to the chemical formula AgBi 3-x S 5.08 The quartz tube is sealed after being vacuumized, and then the quartz tube is placed in a muffle furnace for high-temperature melting reaction; 0.3≤ x ≤0.6; (b) grinding the silver-bismuth-sulfur-based ingot prepared in step (a) into a powder with uniform size in a corundum mortar, and then putting the powder into a graphite mold, pre-pressing and then performing discharge plasma sintering to obtain a dense P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material.

6. The method for preparing the P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material according to claim 5, characterized in that, In step (a), the reaction temperature and time for high-temperature melting reaction are as follows: from room temperature to 450 degrees in 15 hours, holding for 2 hours; from 450 degrees to 600 degrees in 3 hours, holding for 2 hours; from 600 degrees to 1000 degrees in 8 hours, reacting for 5 hours; from 1000 degrees to 600 degrees in 2 hours, holding for 48 hours; and then cooling to room temperature.

7. The preparation method of the P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material according to claim 5, characterized in that, The quartz tube was evacuated to a vacuum pressure of less than 4 x 10 -3 Pa in step (a) and the tube was sealed after that.

8. The method for preparing the P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material according to claim 5, characterized in that, In step (b), when performing discharge plasma sintering, the pressure at both ends of the graphite mold is 50 MPa, the reaction temperature is 450-500 degrees, the reaction time is 5-7 minutes, and then natural cooling to room temperature.

9. Application of the P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material according to any one of claims 1-4 or the P-type silver-bismuth-sulfur-based polycrystalline bulk thermoelectric material prepared by the preparation method according to any one of claims 5-8 in thermoelectric energy conversion.

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