Germanium telluride-based thermoelectric element and preparation method thereof

Abstract

The invention relates to a germanium telluride-based thermoelectric element and a preparation method thereof, and the thermoelectric element has a three-layer sandwich structure, specifically an interface barrier layer, a germanium telluride-based thermoelectric layer and an interface barrier layer. The material of the interface barrier layer is Fe3Ni, FeNi3 or FeCoNi. The germanium telluride thermoelectric element has low interface resistance, the interface structure formed by sintering is reliable and good in stability, interface reaction is effectively inhibited, high conversion efficiency of the thermoelectric element is facilitated, long-term service stability is guaranteed, and the germanium telluride thermoelectric element is simple in preparation method, low in cost and good in practicability.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric devices, and in particular to a germanium telluride-based thermoelectric element and a preparation method thereof. Background Art

[0002] Thermoelectric materials can convert heat and electricity into each other and are widely used in energy utilization and recovery. The global demand for alternative clean energy has significantly driven the rapid development of thermoelectric material research. Germanium telluride (GeTe), a mid-temperature thermoelectric material, exhibits excellent thermoelectric performance between 500K and 773K through heterovalent doping and band degeneracy. This translates to excellent thermoelectric conversion efficiency in corresponding thermoelectric devices. Therefore, the development of GeTe-based thermoelectric devices is of strategic importance, as it will help address my country's current low energy utilization.

[0003] Different thermoelectric material systems have varying requirements for interface materials and processes, creating a host of challenges for the practical application of new thermoelectric systems. From material selection, preparation, and optimization, to electrode material selection and optimization, and ultimately to device construction, operation, and life testing, problems at any stage can lead to performance loss and potentially prevent the practical application of new thermoelectric systems. The conversion efficiency of GeTe-based thermoelectric devices depends not only on the high performance of the thermoelectric materials but also on the quality of the device interface, particularly the interface between the transition layer and the electrode. In medium- and high-temperature devices, the role of the barrier layer becomes even more crucial. It must not only possess high electrical and thermal conductivity but also prevent interdiffusion and chemical reactions between the different elements. Optimizing the electrode interface can significantly improve the conversion efficiency and stability of thermoelectric devices. Furthermore, GeTe undergoes a phase transition between 400 and 700 K. The mismatch in thermal expansion coefficients between the materials can lead to excessive stress at the device junction, potentially leading to failure. Therefore, appropriate interface design is a key challenge in the development of GeTe from materials to devices.

[0004] Therefore, designing suitable interface barrier materials and optimizing interface structures have become key tasks in thermoelectric device research. Existing technologies, such as CN115835757A, use relatively expensive and scarce elements such as germanium. While these technologies achieve promising results, their relatively high costs limit their further application. Summary of the Invention

[0005] In order to overcome the above-mentioned shortcomings of the existing technology, the present invention provides a germanium telluride-based thermoelectric element and a preparation method thereof. The alloy composed of Fe, Ni and Co elements in a specific proportion is used as the interface barrier layer material, so that the GeTe-based thermoelectric device has a low interface resistance. The interface structure formed by sintering is reliable and stable, and the interface reaction is effectively suppressed, which is conducive to achieving high conversion efficiency of the thermoelectric device and ensuring long-term service stability. The preparation method is simple, low-cost, and has good practicality.

[0006] To achieve the above objectives, this application provides the following technical solutions: A germanium telluride-based thermoelectric element has a three-layer sandwich structure, specifically an interface barrier layer-germanium telluride-based thermoelectric layer-interface barrier layer; the material of the interface barrier layer is Fe3Ni, FeNi3 or FeCoNi.

[0007] Furthermore, the thickness of the interface barrier layer is 0.1-2 mm.

[0008] Furthermore, the germanium telluride-based thermoelectric layer has a thickness of 3-5 mm.

[0009] Furthermore, the material of the germanium telluride-based thermoelectric layer is Ge 1-x-y Ln x Bi y Te, where x = 0.05-0.07, y = 0.01-0.05.

[0010] Furthermore, the interface barrier layer is powder obtained by ball milling.

[0011] Furthermore, the germanium telluride-based thermoelectric layer is prepared into a powder by vacuum melting or ball milling, and then into a block by spark plasma sintering technology.

[0012] Furthermore, the present invention also provides a method for preparing the germanium telluride-based thermoelectric element, comprising the following steps: S1) Preparation of germanium telluride-based thermoelectric layer materials and interface barrier layer materials; S2) sequentially loading the interface barrier layer material, the germanium telluride-based thermoelectric layer material, and the interface barrier layer material into a graphite mold and pressing the resulting material into the germanium telluride-based thermoelectric element.

[0013] Furthermore, in step S1), each elemental powder of the germanium telluride-based thermoelectric layer material is weighed in an argon-filled glove box, placed in a pre-prepared quartz tube, and vacuum-sealed. The sealed quartz tube is heated from room temperature to between 1173 and 1373 K at a rate of 1-2 K / min, kept warm for 10-14 hours, and then cooled to room temperature at a cooling rate of 1-2 K / min. After removing the quartz tube from the box furnace, the quartz tube is broken with a heavy object to obtain a melt-cooled germanium telluride-based thermoelectric layer material ingot, which is ground into a fine powder using a mortar and sieved using a 325-mesh sieve to obtain a powder of the germanium telluride-based thermoelectric layer material.

[0014] Furthermore, in step S1), in a glove box filled with an argon environment, the individual elemental powders of the interface barrier layer material are loaded into a ball mill jar according to a certain stoichiometric ratio and sealed. The sealed ball mill jar is loaded on a planetary ball mill, the rotation speed is set between 400-600 rad / min, and the ball milling time is set between 8-15 hours to obtain a powder of the interface barrier layer material.

[0015] Furthermore, in step S2), the pressing process is specifically as follows: the graphite mold is quickly transferred to a spark plasma sintering furnace, the initial vertical pressure is set to 30 MPa, the temperature is raised to between 400-600°C within 10-12 minutes, and the temperature is kept at this temperature for 10-30 minutes. The temperature is lowered to room temperature within 2 hours to 2.5 hours using a cooling program, and the pressure is released. The vertical pressure is set to 10-20 MPa, and the pressure is released to 0 MPa after the program is completed.

[0016] Beneficial effects:

[0017] The present invention uses an alloy composed of Fe, Ni and Co elements in a specific proportion as the interface barrier layer material, so that the GeTe-based thermoelectric device has a low interface resistance. The interface structure formed by sintering is reliable and stable, and the interface reaction is effectively suppressed, which is conducive to the thermoelectric device achieving high conversion efficiency and ensuring long-term service stability. The preparation method is simple, low-cost, and has good practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a graph showing the interface resistance test results of Example 1 of the present invention; Figure 2 This is a graph showing the interface resistance test results after aging in Example 1 of the present invention; Figure 3 This is a graph showing the interface resistance test results of Example 2 of the present invention; Figure 4 This is a graph showing the interface resistance test results after aging in Example 2 of the present invention; Figure 5 This is a graph showing the interface resistance test results of Example 3 of the present invention; Figure 6 This is a graph showing the interface resistance test results after aging in Example 3 of the present invention; Figure 7 This is a graph showing the interface resistance test results of Comparative Example 1 of the present invention; Figure 8 This is a graph showing the interface resistance test results after aging of Comparative Example 1 of the present invention; Figure 9 This is a graph showing the interface resistance test results of Comparative Example 2 of the present invention; Figure 10 This is a graph showing the interface resistance test results after aging in Comparative Example 2 of the present invention; Figure 11 This is a graph showing the interface resistance test results of Comparative Example 3 of the present invention; Figure 12 This is a graph showing the interface resistance test results after aging for comparative example 3 of the present invention. DETAILED DESCRIPTION

[0019] The technical solutions provided by the present invention are described more clearly below with reference to the embodiments and drawings, but the scope of protection claimed by the present invention is not limited to the following embodiments.

[0020] Example 1:

[0021] (1) In a glove box filled with argon, weigh Ge 0.915 Lu 0.015 Bi 0.07 6g of various Te powders were placed in a pre-prepared quartz tube and sealed under vacuum. The sealed tube was heated from room temperature to 1273K at a rate of 2K / min, held for 12 hours, and then cooled to room temperature over 12 hours using programmed cooling. After removing the quartz tube from the box furnace, the tube was broken with a heavy object to obtain a melted and cooled GeTe ingot. This ingot was then ground into a fine powder in a mortar and sieved through a 325-mesh sieve to obtain a GeTe-based thermoelectric material powder.

[0022] (2) In a glove box, weigh the corresponding iron and nickel powder raw materials according to the molar ratio of each element in the Fe3Ni chemical formula, put them into a ball mill, set the speed at 600 rad / min, and set the ball milling time at 12 h to obtain the powder of the barrier layer material.

[0023] (3) The obtained powder was loaded into a graphite mold according to the three-layer structure of "interface barrier material-GeTe-based thermoelectric material-interface barrier material" and quickly transferred to a spark plasma sintering furnace. The initial vertical pressure was set to 30 MPa, the temperature was raised to 550°C within 12 minutes, and the temperature was kept at this temperature for 20 minutes. The temperature was lowered to room temperature within 2 hours using a cooling program, and the pressure was released. The vertical pressure was set to 10 MPa, and the pressure was released to 0 MPa after the program was completed. The germanium telluride-based thermoelectric element of Example 1 was obtained, and the thickness of the three-layer structure was 1 mm, 3 mm, and 1 mm from top to bottom.

[0024] Example 2:

[0025] The only difference from Example 1 is that the interface barrier layer material is FeNi3, and the germanium telluride-based thermoelectric element of Example 2 is obtained. The thickness of the three-layer structure from top to bottom is 1 mm, 3.2 mm and 1 mm respectively.

[0026] Example 3:

[0027] The only difference from Example 1 is that the interface barrier layer material is FeCoNi, and the germanium telluride-based thermoelectric element of Example 3 is obtained. The thickness of the three-layer structure is 1.2 mm, 3 mm and 1.2 mm from top to bottom.

[0028] Comparative Example 1: The only difference from Example 1 is that the interface barrier layer material is FeNi, and the germanium telluride-based thermoelectric element of Comparative Example 1 is obtained, and the thicknesses of the three-layer structure from top to bottom are 1.5 mm, 3.5 mm and 1.5 mm respectively.

[0029] Comparative Example 2: The only difference from Example 1 is that the interface barrier layer material is Fe2CoNi, and the germanium telluride-based thermoelectric element of Comparative Example 2 is obtained. The thickness of the three-layer structure is 1 mm, 4 mm and 1 mm from top to bottom.

[0030] Comparative Example 3: The only difference from Example 1 is that the interface barrier layer material is FeCoNi2, and the germanium telluride-based thermoelectric element of Comparative Example 3 is obtained. The thickness of the three-layer structure is 1.2 mm, 4.3 mm and 1.2 mm from top to bottom.

[0031] Performance test comparison: The germanium telluride-based thermoelectric elements obtained in Examples 1-3 and Comparative Examples 1-3 were cut into desired shapes using diamond wire and their interface resistances were tested. The results are shown in Figure 2. Figure 1 、 3, 5, 7, 9, and 11. The thermoelectric element obtained after cutting was aged at 773K for 6 days, and the interface resistance of the aged sample was tested at the same time. The results are shown in Figure 2 、 4 , 6, 8, 10, and 12.

[0032] The results show that the germanium telluride-based thermoelectric elements obtained in Examples 1-3 have good electrical properties, and their contact resistivity is at a low level, ranging from 1.835 to 2.7 μΩ•cm. 2 After 6 days of aging treatment, the germanium telluride-based thermoelectric element showed good interface stability. The contact resistivity of the germanium telluride-based thermoelectric element after aging treatment was 2.973-4.45μΩ•cm 2 , with an increase of only 60-65%. However, compared with Examples 1-3, each data point of Comparative Example 1 shows poor overall performance, with both initial performance and interface stability after aging being relatively inferior. Although the initial contact resistivity of Comparative Examples 2 and 3 was also relatively low, their interface stability was insufficient, and the contact resistivity increased significantly after aging. In particular, the increase in contact resistivity of Comparative Example 3 after aging reached 175%, indicating that the thermoelectric element interface degraded severely during the aging process, and the interface stability was relatively low.

[0033] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A germanium telluride-based thermoelectric element, characterized in that: The thermoelectric element has a three-layer sandwich structure, specifically an interface barrier layer-germanium telluride-based thermoelectric layer-interface barrier layer; the material of the interface barrier layer is Fe3Ni, FeNi3 or FeCoNi.

2. The germanium telluride-based thermoelectric element according to claim 1, characterized in that: The thickness of the interface barrier layer is 0.1-2 mm.

3. The germanium telluride-based thermoelectric element according to claim 1, characterized in that: The thickness of the germanium telluride-based thermoelectric layer is 3-5 mm.

4. The germanium telluride-based thermoelectric element according to claim 1, characterized in that: The material of the germanium telluride-based thermoelectric layer is Ge 1-x-y Ln x Bi y Te, where x = 0.05-0.07, y = 0.01-0.

05.

5. The germanium telluride-based thermoelectric element according to claim 1, characterized in that: The interface barrier layer is powder obtained by ball milling.

6. The germanium telluride-based thermoelectric element according to claim 1, characterized in that: The germanium telluride-based thermoelectric layer is prepared by synthesizing powder by a vacuum melting method or a ball milling method, and then prepared into a block by combining the spark plasma sintering technology.

7. A method for preparing the germanium telluride-based thermoelectric element according to any one of claims 1 to 6, characterized in that: The steps include: S1) Preparation of germanium telluride-based thermoelectric layer materials and interface barrier layer materials; S2) sequentially loading the interface barrier layer material, the germanium telluride-based thermoelectric layer material, and the interface barrier layer material into a graphite mold and pressing the resulting material into the germanium telluride-based thermoelectric element.

8. The method according to claim 7, characterized in that In step S1), each elemental powder of the germanium telluride-based thermoelectric layer material is weighed in an argon-filled glove box, placed in a pre-prepared quartz tube, and vacuum-sealed. The sealed quartz tube is heated from room temperature to between 1173 and 1373 K at a rate of 1 to 2 K / min, kept warm for 10 to 14 hours, and then cooled to room temperature at a rate of 1 to 2 K / min. After removing the quartz tube from the box furnace, the quartz tube is broken with a heavy object to obtain a melted and cooled germanium telluride-based thermoelectric layer material ingot, which is ground into a fine powder using a mortar and pestle and sieved using a 325-mesh sieve to obtain a powder of the germanium telluride-based thermoelectric layer material.

9. The method according to claim 7, characterized in that In step S1), in an argon-filled glove box, the individual elemental powders of the interface barrier layer material are placed in a sealed ball mill according to a specific stoichiometric ratio. The sealed ball mill is then loaded onto a planetary ball mill at a speed of 400-600 rad / min and a milling time of 8-15 hours to obtain a powder of the interface barrier layer material.

10. The method according to claim 7, characterized in that In step S2), the pressing process is specifically as follows: the graphite mold is quickly transferred to a spark plasma sintering furnace, the initial vertical pressure is set to 30 MPa, the temperature is raised to between 400-600°C within 10-12 minutes, and the temperature is kept at this temperature for 10-30 minutes. The temperature is then lowered to room temperature within 2 hours to 2.5 hours using a cooling program, and the pressure is released. The vertical pressure is set to 10-20 MPa, and the pressure is released to 0 MPa after the program is completed.

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