P-type GexPb1-xTe / BiySb2-yTe3 functional gradient thermoelectric material alloy and preparation method thereof

Abstract

The invention discloses a P-type GexPb1-xTe / BiySb2-yTe3 functional gradient thermoelectric material alloy and a preparation method thereof, and belongs to the technical field of thermoelectric materials.A secondary hot pressing method is adopted, a GexPb1-xTe material alloy ingot with a certain thickness is prepared firstly, then BiySb2-yTe3 material powder is pressed on the GexPb1-xTe material alloy ingot, and the GexPb1-xTe / BiySb2-yTe3 functional gradient thermoelectric material alloy is obtained. And multiple layers of mixed materials with different proportions are used as interface transition layers between the two layers, so that the matching of thermal expansion coefficients is realized, and higher reliability and thermoelectric performance are obtained.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, and specifically relates to a highly reliable P-type Ge x Pb 1-x Te / Bi y Sb 2-y Te3 functionally graded thermoelectric alloys and their preparation methods. Background Technology

[0002] Thermoelectric materials are functional materials that convert heat energy into electrical energy. They possess advantages such as no moving parts, no noise, and no pollution, and are widely used in thermoelectric power generation and refrigeration technologies. Thermoelectric power generation devices constructed using thermoelectric materials offer advantages such as high reliability, good safety, long lifespan, stable electrical output parameters even in extreme environments, and require no maintenance and are unaffected by the environment. Thermoelectric conversion efficiency is one of the important indicators for evaluating the electrical performance of thermoelectric power generation devices. Improving device efficiency usually starts with the thermoelectric materials themselves, and using functionally graded materials (FJTs) is an effective way to improve the thermoelectric conversion efficiency of materials. FJTs refer to materials that are not homogeneous but composed of thermoelectric materials with multiple temperature systems. Different temperature systems of thermoelectric materials are selected according to different operating temperature gradients, and each material can operate within its highest efficiency operating temperature range, thus optimizing the electrical performance of the device.

[0003] Taking a thermoelectric power generation device suitable for medium temperatures as an example, the hot-end operating temperature of the device is approximately 500℃~600℃, and the cold-end operating temperature is approximately room temperature~100℃. Materials with excellent thermoelectric properties at both medium and low temperatures can be used. BiTe-based materials are the best-performing and most commercially available low-temperature thermoelectric materials, with an optimal operating temperature of room temperature to 200℃. Tellurides are the most widely used medium-temperature thermoelectric materials. GeTe-based materials possess excellent electrical transport properties and thermoelectric performance, making them an outstanding medium-temperature thermoelectric material. Significant technological progress has been made in the development of GeTe-based materials in recent years, with a maximum ZT value exceeding 1.8 at 500℃. Preparation of materials from GeTe... x Pb 1-x Te / Bi y Sb 2-y Functionally graded materials combined with Te3 can enable devices to achieve excellent thermoelectric performance, but the difference in thermal expansion coefficients at the interface of heterogeneous materials is large, and the materials are prone to fracture or detachment at operating temperatures above 100°C. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a P-type Ge x Pb 1-x Te / Bi y Sb 2-yThis study aims to address the problems existing in the Te3 functionally graded thermoelectric alloy and its preparation method.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a P-type Ge x Pb 1-x Te / Bi y Sb 2-y The preparation method of Te3 functionally graded thermoelectric alloy includes the following steps: (1) Get Ge x Pb 1-x Te (0.1≤x≤0.2) powder is loaded into a hot pressing mold and hot-pressed into Ge under a vacuum degree better than 0.1Pa. x Pb 1-x Te alloy ingots; (2) General x Pb 1-x Te (0.1≤x≤0.2) powder and Bi y Sb 2-y Te3 (0.5≤y≤1) powder is mixed in three different weight ratios, of which Ge x Pb 1-x The proportions of Te powder in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively; (3) The Ge obtained by hot pressing in step (1) x Pb 1-x The oxide layer on the surface of the Te alloy ingot was cleaned with sandpaper, and then the powder remaining from the polishing process was removed with an alcohol swab. (4) The processed Ge x Pb 1-x The Te alloy ingot was placed back into the hot press mold, and the Ge alloy prepared in step (2) was poured in sequentially. x Pb 1-x The proportions of Te powder in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively. x Pb 1-x Te powder and Bi y Sb 2-y Te3 powder mixture, after each powder is poured in, spread evenly with a tool and then compacted; (5) Bi y Sb 2-y Te3 powder is loaded into the top layer of a hot pressing mold and hot-pressed into an alloy ingot under a vacuum of better than 0.1 Pa. (6) The hot-pressed material ingots are annealed in a tube furnace to obtain P-type Ge x Pb 1-x Te / Bi y Sb2-y Te3 functionally graded thermoelectric alloy.

[0006] Furthermore, in step (1), the hot pressing pressure is 50MPa~70MPa, the hot pressing temperature is 550℃±10℃, and the holding time is 15min~25min.

[0007] Furthermore, in step (5), the hot pressing pressure is 50MPa~70MPa, the hot pressing temperature is 450℃±10℃, and the holding time is 15min~25min.

[0008] Furthermore, in step (6), the annealing temperature is 350℃~400℃ and the annealing time is not less than 20h.

[0009] Furthermore, in step (4), each layer of the mixture can be hot-pressed to a thickness of 0.2-0.3 mm.

[0010] Furthermore, in step (5), Bi is added. y Sb 2-y Te3 powder can be hot-pressed to a thickness similar to Ge x Pb 1-x The thickness of the Te alloy ingot is relatively uniform.

[0011] Furthermore, the Ge x Pb 1-x Preparation method of Te powder: (1) Using vacuum-packed high-purity metal Pb blocks, Te blocks, and Ge blocks as starting materials, according to Ge x Pb 1-x Weigh the raw materials according to the stoichiometry of Te (0.1≤x≤0.2) and place the raw materials into a graphite crucible; (2) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 900℃~1000℃ and the melting time is 0.5h~1h. (3) Ge after smelting x Pb 1-x Te alloy and stainless steel balls were loaded into a stainless steel container at a weight ratio of 20:1. The container was then placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 8-10 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The resulting alloy powder was then sieved through a 200-mesh sieve to obtain Ge alloy. x Pb 01-x Te powder.

[0012] Furthermore, the Bi x Sb 2-x Preparation method of Te3 powder: (1) Using vacuum-packed high-purity metal blocks (Bi, Te, and Sb) as starting materials, according to Bi x Sb 2-x The raw materials for Te3 (0.5≤y≤1) are weighed stoichiometrically and placed in a graphite crucible. (2) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 800℃~900℃ and the melting time is 0.5h~1h. (3) The smelted alloy and stainless steel balls were loaded into a stainless steel jar, with a weight ratio of stainless steel balls to ingots of 20:1. The stainless steel jar was placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 10-15 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The alloy powder obtained after ball milling was sieved through a 200-mesh sieve to obtain Bi. x Sb 2-x Te3 powder.

[0013] Furthermore, the purity of the high-purity metals is: Pb 99%, Te 99.99%, Ge 99.99%, and Bi 99%.

[0014] The p-type Ge prepared by the above method x Pb 1-x Te / Bi y Sb 2-y Te3 functionally graded thermoelectric alloy.

[0015] The beneficial effects of this invention are: by using a secondary hot pressing method, a Ge layer of a certain thickness is first prepared. x Pb 1-x Te material alloy ingot block, then Bi y Sb 2-y Te3 material powder is pressed into Ge x Pb 1-x Te alloy ingots are used as an interface transition layer between the two with multiple layers of mixed materials in different proportions to achieve matching of thermal expansion coefficients, thereby obtaining high reliability and thermoelectric performance. Attached Figure Description

[0016] Figure 1 P-type Ge 0.85 Pb 0.15 Te / Bi 0.4 Sb 1.6 Flowchart of the preparation method of Te3 functional graded thermoelectric material alloy.

[0017] Figure 2 P-type Ge 0.85 Pb 0.15 Te / Bi0.4 Sb 1.6 Backscattered electron image of the Te3 material interface.

[0018] Figure 3 Ge of the sample after 30 days of heat treatment 0.85 Pb 0.15 Te materials and mixtures 1 transition layer interface, Bi 0.4 Sb 1.6 A 1000x backscattered electron image of the interface between Te3 material and the 3-layer transition layer of the mixture.

[0019] Figure 4 To adopt P-type Ge 0.85 Pb 0.15 Te / Bi 0.4 Sb 1.6 A comparison of the test results of the maximum output power versus time curves of a thermoelectric power generation device made of Te3 material combined with N-type PbTe-based material and a thermoelectric power generation device made of elemental GeTe-based material combined with N-type PbTe-based material. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] like Figure 1 As shown, the P-type Ge of the present invention x Pb 1-x Te / Bi y Sb 2-y Te3 functionally graded thermoelectric alloy and its preparation method include the following steps: (1) Using vacuum-packed high-purity metals Pb (99%, in blocks), Te (99.99%, in blocks), and Ge (99.99%, in blocks) as starting materials, according to Ge x Pb 1-x Weigh the raw materials according to the stoichiometry of Te (0.1≤x≤0.2) and place the raw materials into a graphite crucible; (2) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 900℃~1000℃ and the melting time is 0.5h~1h. (3) Ge after smelting x Pb 1-xTe alloy and stainless steel balls were loaded into a stainless steel container at a weight ratio of 20:1. The container was then placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 8-10 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The resulting alloy powder was then sieved through a 200-mesh sieve to obtain Ge alloy. x Pb 1-x Te powder; (4) Part of the Ge after ball milling x Pb 1-x Te powder is loaded into a hot pressing mold and hot-pressed into an alloy ingot under a vacuum of better than 0.1 Pa. The hot pressing pressure is 50 MPa to 70 MPa, the hot pressing temperature is 550℃ ± 10℃, and the holding time is 15 min to 25 min. (5) Using vacuum-packed high-purity metals Bi (99%, in bulk), Te (99.99%, in bulk), and Sb (99.99%, in bulk) as starting materials, according to Bi... y Sb 2-y The raw materials for Te3 (0.5≤y≤1) are weighed stoichiometrically and placed in a graphite crucible. (6) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 800℃~900℃ and the melting time is 0.5h~1h. (7) The smelted alloy and stainless steel balls were loaded into a stainless steel jar, with a weight ratio of stainless steel balls to ingots of 20:1. The stainless steel jar was placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 10-15 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The alloy powder obtained after ball milling was sieved through a 200-mesh sieve to obtain Bi. y Sb 2-y Te3 powder; (8) Another part of Ge x Pb 1-x Te powder and a portion of Bi y Sb 2-y Te3 powder is mixed in three different weight ratios, of which Ge x Pb 1-x The proportions of Te powder by weight in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively; (9) The Ge obtained by hot pressing in step (4) x Pb 1-x The oxide layer on the surface of the Te alloy ingot was cleaned with sandpaper, and then the powder remaining from the polishing process was removed with an alcohol swab. (10) The processed Gex Pb 1-x The Te alloy ingot was placed back into the graphite mold, and the Ge alloy obtained in step (8) was poured in sequentially. x Pb 1-x Te powder and Bi y Sb 2-y Te3 powder mixture, Ge x Pb 1-x The proportions of Te powder in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively. The mixture can be hot-pressed to a thickness of 0.2-0.3mm. After each powder is poured in, it is spread evenly with a special tool and then compacted. (11)Bi y Sb 2-y Te3 powder is loaded into a hot pressing mold and hot-pressed into an alloy ingot under a vacuum of better than 0.1 Pa. The hot pressing pressure is 50 MPa to 70 MPa, the hot pressing temperature is 450℃ ± 10℃, and the holding time is 15 min to 25 min. (12) The hot-pressed material ingots are annealed in a tube furnace at a temperature of 350℃~400℃ for a time of not less than 20h.

[0022] Example (1) According to Ge 0.85 Pb 0.15 Te and Bi 0.4 Sb 1.6 The atomic weights of each component in the chemical formula of Te3 were weighed from the raw materials. The mass of each of the two alloy components was approximately 60g. The required weights of the elemental substances for both alloy components are shown in Table 1. The final ingot dimensions were controlled to be φ25mm × 20mm. Elemental Ge... 0.85 Pb 0.15 Te materials and Bi 0.4 Sb 1.6 The Te3 materials are approximately equal in height; Table 1Ge 0.85 Pb 0.15 Te and Bi 0.4 Sb 1.6 The weight of the elemental substance required for Te3 alloy

[0023] (2) Clean the graphite crucible with an ultrasonic cleaner for 20 minutes. After taking it out, wipe the inside and outside of the graphite crucible with anhydrous ethanol, and then place it in a forced-air drying oven until it is completely dry. (3) According to the calculated Ge 0.85 Pb 0.15The mass of each element in the Te alloy was weighed using a balance. After weighing, the raw material was placed in a graphite crucible. The graphite crucible was then placed in a high-frequency melting equipment. The melting temperature was set to 950℃, the melting time was 1 hour, the heating time was 10 minutes, and the cooling time was natural furnace cooling. After the material was completely cooled to room temperature, the GeTe melted ingot sample was taken out of the equipment. (2) Take another graphite crucible, clean it with an ultrasonic cleaner for 20 minutes, take it out and wipe the inside and outside of the graphite crucible with anhydrous ethanol, and then place it in a forced-air drying oven until it is completely dry. (3) According to the calculated Bi 0.4 Sb 1.6 The mass of each element in the Te3 alloy was weighed using a balance. After weighing, the raw material was placed in a graphite crucible. The graphite crucible was then placed in a high-frequency melting equipment. The melting temperature was set to 850℃, the melting time was 0.5h, the heating time was 10min, and the cooling time was natural furnace cooling. After the material was completely cooled to room temperature, the Bi2Te3 melted ingot sample was taken out of the equipment. (4) The smelted Ge was processed using a planetary ball mill. 0.85 Pb 0.15 Te alloys and Bi 0.4 Sb 1.6 Te3 alloy was ball-milled, with alloy and stainless steel balls loaded into a stainless steel jar. The weight ratio of stainless steel balls to ingots was 20:1, and the rotation speed was fixed at 350 rpm. 0.85 Pb 0.15 The grinding time for Te alloy is 10 hours, and for Bi... 0.4 Sb 1.6 The grinding time for Te3 alloy is 12 hours. During the grinding process, the sealed container is filled with nitrogen to prevent oxidation. (5) The alloy powder obtained after ball milling was sieved through a 200-mesh sieve to obtain Ge 0.85 Pb 0.15 Te powder and Bi 0.4 Sb 1.6 Te3 powder; (6) Take 30g of ball-milled Ge 0.85 Pb 0.15 Te powder is loaded into a hot press mold with a diameter of 25 mm. The temperature is raised in an environment with a vacuum degree better than 0.1 Pa. When the temperature of the vacuum hot press furnace reaches 550℃, a pressure of 55 MPa is applied and the pressure holding time is 20 min. (7) Will Ge 0.85 Pb 0.15 Te powder and Bi 0.4 Sb 1.6 Te3 powder was uniformly mixed into three mixtures according to the weights shown in Table 2.

[0024] Table 2 shows the required weight of each powder for the three mixtures.

[0025] (8) The hot-pressed Ge 0.85 Pb 0.15 The oxide layer on the surface of the Te alloy ingot is cleaned with sandpaper, and the powder remaining in the grinding process is removed with alcohol cotton. The ingot is put back into the graphite mold, and mixture 1, mixture 2 and mixture 3 are poured in sequence. After each mixture powder is poured in, it is spread evenly with a special tool and then compacted. (9) Take 35g of ball-milled Bi 0.4 Sb 1.6 Te3 powder is loaded into a hot press mold and heated in an environment with a vacuum degree better than 0.1 Pa. When the temperature of the vacuum hot press furnace reaches 450℃, a pressure of 55MPa is applied and the holding time is 20min. (10) The hot-pressed material ingots are annealed in a tube furnace at a temperature of 400°C for 1220 min.

[0026] (11) During the work process, Ge 0.85 Pb 0.15 Te, Bi 0.4 Sb 1.6 The temperature at the transition layer between the two Te3 materials is approximately 200℃~250℃. The prepared alloy was placed in an annealing furnace and heated to 250℃, and held at this temperature for 5 days, 10 days, and 30 days for aging tests. The condition of the transition layer between the two materials after the aging tests was observed under an EDS scanning electron microscope. Figure 2 As can be seen from the backscattered electron image of the interface, Ge before aging 0.85 Pb 0.15 Te, Bi 0.4 Sb 1.6 The transition layer of the two Te3 materials was tightly bonded, and no obvious cracks were observed in the sample. With the increase of heat treatment time, the structure of the transition layer did not change significantly. The sample after 30 days of heat treatment still maintained good interfacial bonding, and no obvious cracks were observed in the sample. The phase distribution in the transition layer did not change significantly. Figure 3 The image shows the Ge content of the sample after 30 days of heat treatment. 0.85 Pb 0.15 Te materials and mixtures 1 transition layer interface, Bi 0.4 Sb 1.6 A 1000x backscattered electron image of the interface between Te3 material and the mixture 3 transition layer. All samples are tightly bonded at the interface with no obvious microcracks. The transition layer material diffuses along the grain boundaries into the bulk material.

[0027] (12) Using P-type Ge 0.85 Pb0.15 Te / Bi 0.4 Sb 1.6 Thermoelectric power generation devices were fabricated using Te3 materials combined with N-type PbTe-based materials, and their maximum output power was tested. Simultaneously, thermoelectric power generation devices fabricated using elemental GeTe-based materials combined with N-type PbTe-based materials were also tested. Figure 4 The figure shows a comparison of the test results of the maximum output power variation curves of the two devices over time; the test conditions were the same: the hot surface temperature of the device was maintained at 500℃±2℃ and the cold surface temperature at 50℃±2℃, and the test time was 30 days; the test results show that using P-type Ge 0.85 Pb 0.15 Te / Bi 0.4 Sb 1.6 The thermoelectric power generation device fabricated from Te3 material combined with N-type PbTe-based material had an initial maximum output power of 1.835 W, and after 30 days, its maximum output power was 1.826 W, representing a decrease of only 0.49% compared to the initial maximum output power. Table 3 shows a comparison of the maximum output power of the two devices at the initial and final test times, using P-type Ge3 material. 0.85 Pb 0.15 Te / Bi 0.4 Sb 1.6 Devices fabricated with Te3 materials outperformed devices made with elemental GeTe-based materials by approximately 20%.

[0028] Table 3 Comparison of maximum output power of the two devices at the initial and final times.

[0029] This invention obtains Ge with high reliability x Pb 1-x Te / Bi y Sb 2-y A method for preparing Te3 functionally graded thermoelectric materials effectively improves the thermoelectric conversion efficiency of mid-temperature thermoelectric power generation devices.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A P-type Ge x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, Includes the following steps: (1) Get Ge x Pb 1-x Te (0.1≤x≤0.2) powder is loaded into a hot pressing mold and hot-pressed into Ge under a vacuum degree better than 0.1Pa. x Pb 1-x Te alloy ingots; (2) General x Pb 1-x Te (0.1≤x≤0.2) powder and Bi y Sb 2-y Te3 (0.5≤y≤1) powder is mixed in three different weight ratios, of which Ge x Pb 1-x The proportions of Te powder in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively; (3) The Ge obtained by hot pressing in step (1) x Pb 1-x The oxide layer on the surface of the Te alloy ingot was cleaned with sandpaper, and then the powder remaining from the polishing process was removed with an alcohol swab. (4) The processed Ge x Pb 1-x The Te alloy ingot was placed back into the hot press mold, and the Ge alloy prepared in step (2) was poured in sequentially. x Pb 1-x The proportions of Te powder in the total weight are 70%~75%, 50%~55%, and 30%~25%, respectively. x Pb 1-x Te powder and Bi y Sb 2-y Te3 powder mixture, after each powder is poured in, spread evenly with a tool and then compacted; (5) Bi y Sb 2-y Te3 powder is loaded into the top layer of a hot pressing mold and hot-pressed into an alloy ingot under a vacuum of better than 0.1 Pa. (6) The hot-pressed material ingots are annealed in a tube furnace to obtain P-type Ge x Pb 1-x Te / Bi y Sb 2-y Te3 functionally graded thermoelectric alloy.

2. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, In step (1), the hot pressing pressure is 50MPa~70MPa, the hot pressing temperature is 550℃±10℃, and the holding time is 15min~25min.

3. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, In step (5), the hot pressing pressure is 50MPa~70MPa, the hot pressing temperature is 450℃±10℃, and the holding time is 15min~25min.

4. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, In step (6), the annealing temperature is 350℃~400℃ and the annealing time is not less than 20h.

5. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, In step (4), each layer of the mixture can be hot-pressed to a thickness of 0.2-0.3 mm.

6. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, In step (5), Bi is added. y Sb 2-y Te3 powder can be hot-pressed to a thickness similar to Ge x Pb 1-x The thickness of the Te alloy ingot is relatively uniform.

7. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, The Ge x Pb 1-x Preparation method of Te powder: (1) Using vacuum-packed high-purity metal Pb blocks, Te blocks, and Ge blocks as starting materials, according to Ge x Pb 1-x Weigh the raw materials according to the stoichiometry of Te (0.1≤x≤0.2) and place the raw materials into a graphite crucible; (2) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 900℃~1000℃ and the melting time is 0.5h~1h. (3) Ge after smelting x Pb 1-x Te alloy and stainless steel balls were loaded into a stainless steel container at a weight ratio of 20:

1. The container was then placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 8-10 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The resulting alloy powder was then sieved through a 200-mesh sieve to obtain Ge alloy. x Pb 01-x Te powder.

8. The P-type Ge according to claim 1 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, The Bi x Sb 2-x Preparation method of Te3 powder: (1) Using vacuum-packed high-purity metal blocks (Bi, Te, and Sb) as starting materials, according to Bi x Sb 2-x The raw materials for Te3 (0.5≤y≤1) are weighed stoichiometrically and placed in a graphite crucible. (2) Place the graphite crucible in a high-frequency melting furnace and evacuate it to below 10 Pa. Then fill it with 0.04 MPa of protective inert gas to start melting. The melting temperature is 800℃~900℃ and the melting time is 0.5h~1h. (3) The smelted alloy and stainless steel balls were loaded into a stainless steel jar, with a weight ratio of stainless steel balls to ingots of 20:

1. The stainless steel jar was placed in a planetary ball mill for ball milling at a fixed speed of 350 rpm for 10-15 hours. During the grinding process, the sealed container was filled with nitrogen to prevent oxidation. The alloy powder obtained after ball milling was sieved through a 200-mesh sieve to obtain Bi. x Sb 2-x Te3 powder.

9. The P-type Ge according to claim 7 or 8 x Pb 1-x Te / Bi y Sb 2-y The method for preparing Te3 functionally graded thermoelectric alloys is characterized by, The purity of high-purity metals is: Pb 99%, Te 99.99%, Ge 99.99%, and Bi 99%.

10. P-type Ge prepared by the preparation method according to any one of claims 1-9 x Pb 1-x Te / Bi y Sb 2-y Te3 functionally graded thermoelectric alloy.

Images