A germanium telluride-based thermoelectric element and its fabrication method

Abstract

This invention discloses a germanium telluride-based thermoelectric element and its fabrication method. The germanium telluride-based thermoelectric element has a structure consisting of an electrode layer / barrier layer / germanium telluride-based thermoelectric layer arranged sequentially in close proximity; the general chemical formula of the germanium telluride-based thermoelectric layer is Ge. 1‑x‑y+δ M x N y Te 1‑z Q z Wherein, 0≤x≤0.03, 0≤y≤0.1, 0≤z≤0.1, 0≤δ≤0.03; M is at least one of Cu, Ag, Sn, In, Sc, Ti, V, Mn, Mg, Pb, and Zn; N is at least one of Sb and Bi; and Q is at least one of Se and S. The barrier layer is made of a germanium-containing alloy, wherein the molar percentage of germanium is 10-80%. The germanium telluride-based thermoelectric element exhibits good interfacial bonding and high stability between the barrier layer and the germanium telluride-based thermoelectric material at high temperatures, and low interfacial contact resistivity at room temperature.

Description

Technical Field

[0001] This invention relates to a germanium telluride-based thermoelectric element and its preparation method, belonging to the field of energy conversion technology. Background Technology

[0002] Thermoelectric devices can utilize the Seebeck effect and Peltier effect to achieve the mutual conversion between thermal energy and electrical energy. They have advantages such as all-solid-state structure, small system size, no pollution or noise, and safety and reliability, and can be widely used in high-tech fields such as space technology, military equipment, and electronics industry.

[0003] Currently, the most mature thermoelectric materials for the mid-temperature range mainly include lead telluride and p-type pagdoctrine. Lead telluride is toxic, and p-type pagdoctrine has poor performance, which severely limits their application in mid-temperature power generation devices. Germanium telluride (GeTe), as a thermoelectric compound that has emerged in recent years, has great potential to become a thermoelectric material for applications in the mid-temperature range. After performance optimization, the thermoelectric figure of merit of germanium telluride-based thermoelectric materials can reach over 2.0. However, most current research on germanium telluride focuses primarily on improving the thermoelectric figure of merit, greatly hindering the practical engineering application of germanium telluride-based thermoelectric materials.

[0004] Common thermoelectric devices are mainly composed of thermoelectric materials, barrier layers, and electrodes. The electrothermal transfer performance and stability between the electrode layer and the barrier layer, and between the barrier layer and the thermoelectric material, are key factors affecting the output performance and service performance of thermoelectric devices. Finding suitable interface bonding materials is one of the key factors in fabricating efficient and stable thermoelectric devices. In recent years, research on interface barrier layers and devices based on germanium telluride has gradually attracted attention. In 2009, Singh et al. used a SnTe / Fe / Ag barrier layer and electrode structure on p-type TAGS-85 material and paired it with n-type PbTe to form a device, achieving an energy conversion efficiency of ~6% (Phys.D:Appl.Phys.,2009,42,015502). YANG et al. used SnTe / Sn as a buffer layer to successfully connect a Ni / Ag barrier layer and electrode structure on GeTe material, and improved the interfacial bonding strength to a certain extent (J.ELECTRON.MATER.,2013,42,359-365). Xing et al. reported that metallic titanium was used as an interfacial barrier layer in germanium telluride-based materials, and the measured room-temperature interfacial resistivity was 134 μΩ cm⁻¹. 2 (Natl.Sci.Rev.,2019,6:944–954). Li et al. studied Al 66 Si 34As an interfacial barrier layer for germanium telluride-based materials, after high-temperature aging at 500℃, the tellurium element in the matrix material undergoes a significant diffusion reaction with the Al in the Al66Si34 interface, resulting in an interfacial contact resistivity of 20.7 μΩ cm⁻¹ at room temperature. 2 (ACS Appl. Mater. Interfaces, 2020, 12, 18562-18569). The interfacial contact resistivity of these barrier layers is significantly higher than that of materials such as cobaltite and semi-Hessler, which severely limits the performance output of germanium telluride-based thermoelectric materials. Perumal et al. used Fe as a barrier layer to measure the efficiency of germanium telluride-based single-arm devices, but did not report the relevant performance of the barrier layer interface (Joule, 2019, 3, 1–16). Xing et al. used a high-throughput method to screen out some elemental metals that would diffuse with the matrix and selected molybdenum as the interfacial barrier layer for germanium telluride-based materials. Due to the presence of microcracks inside the fabricated device, the conversion efficiency of the germanium telluride-based thermoelectric device at a temperature difference of 500 K was only 7.8%, far lower than the theoretical efficiency of 11.4% (Energy Environ. Sci., 2021, 14, 995-1003). In addition, Chinese patent CN112670395 A reports that the interfacial resistance is approximately 8 μΩ cm when SnTe is used as a barrier layer. 2 However, Sn will diffuse into the thermoelectric material after aging at high temperature, which will cause the performance of the thermoelectric material to deteriorate and the output performance of the single-arm device to decrease with long-term use.

[0005] This indicates that research on the interfacial barrier layer of germanium telluride-based thermoelectric materials is still in its initial stage, lacking systematic research on issues such as the matching of physical properties between the barrier layer and the thermoelectric material, the interfacial microstructure, and the interfacial construction process. Therefore, developing a germanium telluride-based thermoelectric element with good electrothermal transfer performance and excellent interfacial stability, and proposing a simple and reliable fabrication method for this element, have become urgent technical problems to be solved. Summary of the Invention

[0006] To overcome the above-mentioned shortcomings of the existing technology, the present invention provides a germanium telluride-based thermoelectric element with stable interface and its preparation method. The germanium telluride-based thermoelectric element has good interfacial bonding and high stability between the barrier layer and the germanium telluride-based thermoelectric material at high temperature, and low interfacial contact resistivity at room temperature.

[0007] In a first aspect, the present invention provides a germanium telluride-based thermoelectric element. The germanium telluride-based thermoelectric element has a structure comprising an electrode layer / barrier layer / germanium telluride-based thermoelectric layer arranged sequentially in close proximity; the general chemical formula of the germanium telluride-based thermoelectric layer is Ge. 1-x-y+δ M x N y Te 1-z Qz x and y represent the molar percentages of M and N elements doped at the Ge sites, respectively. δ represents the adjustment of the Ge site element within a certain range. z represents the molar percentage of Q element doped at the Te sites. Wherein, 0 ≤ x ≤ 0.03, 0 ≤ y ≤ 0.1, 0 ≤ z ≤ 0.1, and 0 ≤ δ ≤ 0.03. M is at least one of Cu, Ag, Sn, In, Sc, Ti, V, Mn, Mg, Pb, and Zn. N is at least one of Sb and Bi. Q is at least one of Se and S. The barrier layer is made of a germanium-containing alloy, wherein the molar percentage of germanium is 10–80%.

[0008] This invention achieves a match between the physical performance parameters and microstructure of the barrier layer and the germanium telluride-based thermoelectric layer by controlling the chemical composition design. This effectively suppresses the diffusion reaction of tellurium with the electrode, improving the reliability and service life of the germanium telluride-based thermoelectric element. The barrier layer exhibits excellent bonding with the germanium telluride matrix material because the germanium telluride-based thermoelectric material described in this invention contains a small amount of germanium second phase. The germanium alloy barrier layer can directly bond with the germanium telluride-based thermoelectric material at high temperatures. Furthermore, by designing the barrier layer composition to adjust the thermal expansion coefficient of the alloy interface to match the thermoelectric material, the bonding strength between the barrier layer and the germanium telluride-based thermoelectric layer structure is significantly increased. On the other hand, the barrier layer alloy of the present invention is more thermodynamically stable. That is, the metal elements in the alloy interface tend to form compounds with germanium at high temperatures, rather than diffuse and react with tellurium to form a diffusion layer. This effectively solves the problem of reaction between the barrier layer interface and thermoelectric materials reported in the literature, and also suppresses the diffusion reaction between germanium telluride thermoelectric materials and electrodes, thus achieving the effect of a barrier layer interface. Finally, the resistivity of the germanium-containing alloy is lower than that of germanium telluride-based thermoelectric materials, and its thermal conductivity is higher than that of thermoelectric materials. Therefore, the interfacial resistivity between the two is very low, which can well meet the electrothermal transfer performance of thermoelectric elements.

[0009] Preferably, the barrier layer is an alloy of germanium and at least one of nickel, niobium, chromium, cobalt, iron, copper, aluminum, molybdenum, and scandium.

[0010] Preferably, the thickness of the electrode layer is 10 to 2000 micrometers, more preferably 100 to 1000 micrometers; the thickness of the barrier layer is 10 to 1000 micrometers, more preferably 50 to 150 micrometers; and the thickness of the germanium telluride-based thermoelectric layer is 0.01 to 200 millimeters, more preferably 3 to 20 millimeters.

[0011] Preferably, the thickness ratio of the electrode layer, the barrier layer, and the germanium telluride-based thermoelectric layer is 10–20:1–2:80–300. This thickness ratio is beneficial for increasing the bonding strength of the layer structure, while also maximizing the output performance of the germanium telluride-based thermoelectric element.

[0012] Preferably, the room temperature interfacial resistivity of the germanium telluride-based thermoelectric element is less than 1 μΩ cm. 2 The interface contact resistivity is the product of the sum of the contact resistance between the electrode layer and the barrier layer, the resistance of the barrier layer itself, and the contact resistance between the barrier layer and the germanium telluride-based thermoelectric layer, and the interface cross-sectional area.

[0013] Preferably, the electrode layer is a metal or alloy, preferably at least one of elemental nickel, elemental copper, nickel-copper alloy, and molybdenum-copper alloy, wherein the molar percentage of copper in the nickel-copper alloy and the molybdenum-copper alloy is 20-80%.

[0014] Secondly, the present invention also provides a method for preparing the germanium telluride-based thermoelectric element as described in any of the above claims. The preparation method is a one-step sintering method, comprising: sequentially loading a germanium telluride-based thermoelectric material, a barrier layer material, and an electrode layer material into a mold, and performing discharge plasma sintering or hot-pressing sintering in a vacuum or inert protective atmosphere to obtain the germanium telluride-based thermoelectric element; or, the preparation method is a high-temperature welding method, comprising: sequentially loading a germanium telluride-based thermoelectric layer material and a barrier layer material into a mold, and performing discharge plasma sintering or hot-pressing sintering in a vacuum or inert protective atmosphere to obtain a sintered block; then welding the sintered block to the electrode layer material at high temperature using solder to obtain the germanium telluride-based thermoelectric element.

[0015] The method for preparing the germanium telluride-based thermoelectric element of the present invention has the advantages of simple process, high reliability and easy mass production. The connection between the electrode layer, the barrier layer and the germanium telluride-based thermoelectric layer is achieved by one-step sintering or high-temperature welding. The interface between the electrode layer and the barrier layer and the interface between the barrier layer and the germanium telluride-based thermoelectric layer are well bonded and have high stability.

[0016] Preferably, the conditions for spark plasma sintering are: heating rate 40–100 °C / min, sintering temperature 540–620 °C, sintering pressure 50–70 MPa, holding time 5–20 minutes, and cooling rate 30–60 °C / min; the conditions for hot pressing sintering are: heating rate 20–80 °C / min, sintering temperature 570–640 °C, sintering pressure 50–70 MPa, holding time 30–75 minutes, and cooling rate 20–50 °C / min.

[0017] Preferably, the welding temperature is 550–640℃, the welding pressure is 2–20MPa, and the welding time is 5–50 minutes.

[0018] The composition of the solder is not limited. Preferably, the solder is a silver-copper alloy, wherein the molar percentage of copper is 20-60%.

[0019] Preferably, the mold includes, but is not limited to, graphite molds, boron nitride molds, or alloy molds. It should be understood that other molds suitable for molding are also applicable to this invention. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a germanium telluride-based thermoelectric element, where 1 is the electrode layer, 2 is the barrier layer, and 3 is the germanium telluride-based thermoelectric layer.

[0021] Figure 2 Micrograph of the interface structure of the thermoelectric element prepared by the one-step sintering method in Example 1;

[0022] Figure 3 The elemental distribution at the interface of the thermoelectric element prepared by the one-step sintering method in Example 1 is shown in the diagram.

[0023] Figure 4 This is a graph showing the resistance variation at the interface of the thermoelectric element prepared by the one-step sintering method in Example 1.

[0024] Figure 5 Micrograph of the interface structure of the thermoelectric element prepared by the high-temperature welding method in Example 2;

[0025] Figure 6 This is a graph showing the resistance variation at the interface of the thermoelectric element prepared by the high-temperature welding method in Example 2.

[0026] Figure 7 Micrographs of the interface structure of the bulk sample prepared by the one-step sintering method in Comparative Example 1;

[0027] Figure 8 The elemental distribution at the interface of the bulk sample prepared by the one-step sintering method in Comparative Example 1 is shown.

[0028] Figure 9 The graph shows the resistance variation at the interface of the bulk sample prepared by the one-step sintering method in Comparative Example 1. Detailed Implementation

[0029] The present invention is further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention. Unless otherwise specified, all percentage contents refer to mass percentage contents.

[0030] The following combination Figure 1 A schematic diagram illustrating the structure of the germanium telluride-based thermoelectric element of the present invention is provided. The thermoelectric element comprises, from one side to the other, a germanium telluride-based thermoelectric layer (also referred to as a "GeTe thermoelectric layer"), a barrier layer, and an electrode layer.

[0031] The general chemical formula of the germanium telluride-based thermoelectric layer is Ge. 1-x-y+δ M x N y Te1-z Q z M is at least one of Cu, Ag, Sn, In, Sc, Ti, V, Mn, Mg, Pb, and Zn; N is at least one of Sb and Bi; and Q is at least one of Se and S. Wherein, 0 ≤ x ≤ 0.03, 0 ≤ y ≤ 0.1, 0 ≤ z ≤ 0.1, and 0 ≤ δ ≤ 0.03.

[0032] In some embodiments, the germanium telluride-based thermoelectric layer has a maximum thermoelectric figure of merit zT greater than 1.5 and an average thermoelectric figure of merit greater than 0.8 in the temperature range of 400–800 K.

[0033] The thickness of the germanium telluride-based thermoelectric layer can be 0.01–200 mm, preferably 3–20 mm. This can largely guarantee the output of the thermoelectric element.

[0034] The barrier layer is made of a germanium-containing alloy, wherein the molar percentage of germanium is 10-80%. Using this barrier layer ensures good bonding between the electrode layer and the barrier layer, low interfacial resistivity, slow interfacial diffusion at high temperatures, and good stability. Preferably, the barrier layer is an alloy composed of germanium and at least one of the elemental metals selected from nickel, niobium, chromium, cobalt, iron, copper, aluminum, molybdenum, and scandium. The barrier layer provided by this invention is applicable to various germanium telluride-based thermoelectric materials, providing excellent barrier layer performance for germanium telluride-based thermoelectric materials with different doping, demonstrating excellent versatility. Furthermore, the coefficient of thermal expansion of the germanium-containing alloy barrier layer can be adjusted by designing its composition to achieve physical parameter matching with the coefficient of thermal expansion of the GeTe thermoelectric layer with different doping (typically between 10 and 24).

[0035] The barrier layer occupies a relatively small proportion of the total thickness of the thermoelectric element. The thickness of the barrier layer is 10–1000 micrometers, preferably 50–150 micrometers. This is beneficial for achieving a barrier connection function.

[0036] The composition of the electrode layer is not limited, and any electrode layer commonly used in the art can be used. Preferably, the electrode layer is at least one of elemental nickel, elemental copper, nickel-copper alloy, and molybdenum-copper alloy. The molar percentage of copper in nickel-copper alloy and molybdenum-copper alloy is 20-80%. More preferably, the electrode layer is elemental nickel or a nickel-containing alloy, in which case the electrode layer has excellent electrical and thermal conductivity.

[0037] The thickness of the electrode layer can be 10 to 2000 micrometers, preferably 100 to 1000 micrometers.

[0038] The room temperature interfacial resistivity of the aforementioned germanium telluride-based thermoelectric element is less than 1 μΩ cm. 2The interface contact resistivity is the product of the sum of the contact resistance between the electrode layer and the barrier layer, the resistance of the barrier layer itself, and the contact resistance between the barrier layer and the germanium telluride-based thermoelectric layer, and the interface cross-sectional area.

[0039] The present invention also provides a method for preparing germanium telluride-based thermoelectric elements that is simple in process, highly reliable, and easy to scale up for production.

[0040] The germanium telluride-based thermoelectric element can be fabricated using a one-step sintering method. The germanium telluride-based thermoelectric material, barrier layer material, and electrode layer material are sequentially loaded into a mold, and then subjected to spark plasma sintering or hot pressing sintering in a vacuum or under an inert protective atmosphere to obtain the germanium telluride-based thermoelectric element. The mold can be a graphite mold. The vacuum level can be 0.1–10 Pa.

[0041] The preparation method of germanium telluride-based thermoelectric materials is unrestricted; they can be obtained commercially or prepared in-house. For example, according to the stoichiometric ratio of germanium telluride-based thermoelectric materials, the raw materials are weighed and placed in a graphite crucible. The graphite crucible is then placed in a quartz tube, and vacuum-sealed when the vacuum level inside the quartz tube is less than 1 Pa. The sealed quartz tube is then placed in a melting furnace and heated to 1100°C at a rate of 100°C / h from room temperature, and held at that temperature for 12 hours, followed by quenching. The quartz tube containing the ingot is then placed in an annealing furnace and heated to 600°C at a rate of 200°C / h from room temperature, and held at that temperature for 5 days. Finally, the resulting bulk sample is ground to obtain the target powder.

[0042] The germanium telluride-based thermoelectric element can also be fabricated using a high-temperature welding method. The germanium telluride-based thermoelectric layer material and the barrier layer material are sequentially loaded into a mold, and then subjected to discharge plasma sintering or hot pressing sintering under a vacuum or inert protective atmosphere to obtain a sintered block. Then, the sintered block is connected to the electrode using solder at high temperature (welding) to obtain the germanium telluride-based thermoelectric element. The mold can be a graphite mold. The vacuum degree can be 0.1–10 Pa.

[0043] The conditions for spark plasma sintering are: heating rate 40–100°C / min, sintering temperature 540–620°C, sintering pressure 50–70 MPa, holding time 5–20 minutes, and cooling rate 30–60°C / min. Preferably, the conditions for spark plasma sintering are: heating rate 60–80°C / min, sintering temperature 540–580°C, sintering pressure 50–60 MPa, holding time 8–15 minutes, and cooling rate 30–40°C / min.

[0044] The conditions for hot-press sintering are: heating rate 20–80°C / min, sintering temperature 570–640°C, sintering pressure 50–70 MPa, holding time 30–75 minutes, and cooling rate 20–50°C / min. Preferably, the conditions for hot-press sintering are: heating rate 30–50°C / min, sintering temperature 580–620°C, sintering pressure 50–60 MPa, holding time 40–60 minutes, and cooling rate 30–40°C / min.

[0045] The main component of the above-mentioned solder (high-temperature end welding layer) may be Ag-Cu alloy, wherein the molar percentage of Cu is 20-60%, and the balance is Ag and a small amount of other elements.

[0046] The welding process can be as follows: welding temperature 550–640℃, welding pressure 2–20MPa, and welding time 5–50 minutes. Preferably, the welding process is as follows: welding temperature 580–620℃, welding pressure 5–10MPa, and welding time 10–30 minutes.

[0047] In summary, this invention provides a germanium telluride-based thermoelectric element and its preparation method. The germanium telluride-based thermoelectric element has a barrier layer / thermoelectric material interface structure with low contact resistivity and high reliability, which can realize the connection between the electrode layer, the barrier layer and the germanium telluride-based thermoelectric material. The resulting germanium telluride-based thermoelectric element has good bonding between its interfaces, high stability and low interface contact resistivity.

[0048] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0049] The graphite mold used in this embodiment has an inner diameter of 10 mm, and the powder purity of the electrode material and barrier layer material is above 99%; the germanium telluride-based thermoelectric material (GeTe) has the following composition: Ge 0.89 Cu 0.06 Sb 0.08 Te, δ = 0.03.

[0050] Example 1

[0051] 2.5g of germanium telluride-based thermoelectric material powder, 0.04g of nickel-germanium alloy powder, and 0.06g of nickel powder were weighed out respectively. The germanium telluride-based thermoelectric material powder, nickel-germanium alloy powder, and nickel powder were sequentially placed into a graphite mold with an inner diameter of 10mm, ensuring the flatness between layers, followed by vacuum discharge plasma sintering. During vacuum discharge plasma sintering, the vacuum was evacuated to below 10Pa, and the temperature was raised to the sintering temperature of 540℃ at a rate of 80℃ / min, maintaining a sintering pressure of 50MPa for 10min. Then, the temperature was lowered by 150℃ at a rate of 50℃ / min, and the mold was removed. The sample was cut using a wire EDM machine to obtain a cross-sectional dimension of 3×3mm. 2 Thermoelectric element with a structure of GeTe / NiGe / Ni.

[0052] Figure 2 From right to left, the layers are the electrode layer, the barrier layer, and the germanium telluride-based thermoelectric layer. The interface between the nickel-germanium alloy barrier layer and the germanium telluride-based thermoelectric material GeTe is well bonded, with no obvious cracks or voids.

[0053] Figure 3 The elemental distribution shows that the elements are evenly distributed, and there is no obvious diffusion or chemical reaction at the interface. This confirms that the one-step sintered barrier layer nickel-germanium alloy and the germanium telluride-based thermoelectric material GeTe have good interfacial bonding.

[0054] Figure 4 This is a graph showing the resistance variation at the interface obtained by measuring the germanium telluride-based thermoelectric element prepared in Example 1 using the four-probe method. The interface contact resistivity is the product of the sum of the contact resistance between the electrode layer and the barrier layer, the resistance of the barrier layer itself, and the contact resistance between the barrier layer and the germanium telluride-based thermoelectric layer, and the interface cross-sectional area. Figure 4 It can be seen that the room temperature contact resistivity at the interface in Example 1 is less than 1 μΩ cm. 2 .

[0055] The germanium telluride-based thermoelectric device prepared in Example 1 has a good interfacial bonding state and low room temperature contact resistivity, which meets the requirements for the use of germanium telluride-based thermoelectric elements.

[0056] Example 2

[0057] 2.5 g of germanium telluride-based thermoelectric material powder and 0.04 g of nickel-germanium alloy powder were weighed out. The germanium telluride-based thermoelectric material powder and nickel-germanium alloy powder were sequentially placed into a graphite mold with an inner diameter of 10 mm, ensuring the flatness between layers, followed by vacuum hot pressing sintering. During vacuum hot pressing sintering, the vacuum was evacuated to below 10 Pa, and the temperature was increased to 600 °C at a rate of 30 °C / min, maintaining a sintering pressure of 60 MPa for 50 min. Then, the temperature was cooled to room temperature at a rate of 30 °C / min, and the mold was removed. The sample was cut using a wire EDM machine to obtain a cross-sectional dimension of 4 × 4 mm. 2 A bulk structure of GeTe / NiGe was prepared. Then, high-temperature welding was performed at 600℃, with the sintered bulk, weld layer, and molybdenum-copper electrode placed sequentially. The welding pressure was 5 MPa, and the time was 15 minutes. After welding, a thermoelectric element with a GeTe / NiGe / Mo-Cu structure was obtained.

[0058] from Figure 5 It can be seen that the interface between the electrode layer Mo-Cu, the welding layer, the barrier layer NiGe and the germanium telluride-based thermoelectric material GeTe in Example 2 is tightly bonded.

[0059] Figure 6 The room temperature interfacial contact resistivity of Example 2 is shown to be less than 1 μΩ cm. 2 .

[0060] Comparative Example 1

[0061] 2.5g of germanium telluride-based thermoelectric material powder, 0.04g of nickel-germanium alloy powder, 0.06g of nickel powder, and 2.5g of germanium telluride-based thermoelectric material powder were weighed out respectively. They were then placed into a graphite mold with an inner diameter of 10mm in the order of germanium telluride-based thermoelectric material powder, nickel-germanium alloy powder, nickel powder, and germanium telluride-based thermoelectric material powder, ensuring the flatness between layers. Subsequently, sintering was performed using the vacuum discharge plasma sintering method described in Example 1 to prepare a bulk GeTe / NiGe / Ni / GeTe structure.

[0062] from Figure 7 and Figure 8 It can be seen that the NiGe alloy in Comparative Example 1 is well bonded to the germanium telluride-based thermoelectric material, while a significant diffusion reaction occurs at the interface between Ni metal and the germanium telluride-based material. Figure 9 The results show that the NiGe alloy interface resistivity in Comparative Example 1 is less than 1 μΩ cm², while the Ni metal interface resistivity is 38.4 μΩ cm². 2 This indicates that it is not suitable as a barrier layer interface.

[0063] Comparative Example 1 simultaneously constructed interfaces between NiGe alloy, elemental Ni metal, and germanium telluride-based thermoelectric materials. It is evident that elemental Ni metal is not suitable as a barrier layer for germanium telluride-based thermoelectric materials, which further confirms the superiority of germanium-containing alloys such as NiGe as barrier layers.

Claims

1. A germanium telluride-based thermoelectric element, characterized by, The germanium telluride-based thermoelectric element has an electrode layer / barrier layer / germanium telluride-based thermoelectric layer structure arranged in sequence; the chemical general formula of the germanium telluride-based thermoelectric layer is Ge 1-x-y+δ M x N y Te 1- z Q z , wherein, 0<=x<=0.03, 0<=y<=0.1, 0<=z<=0.1, 0<=delta<=0.03; M is at least one of Cu, Ag, Sn, In, Sc, Ti, V, Mn, Mg, Pb, Zn, N is at least one of Sb, Bi, Q is at least one of Se, S; the material of the barrier layer is a germanium-containing alloy composed of germanium and at least one of nickel, niobium, chromium, cobalt, iron, copper, aluminum, molybdenum, scandium, wherein the mole percentage of germanium is 10%-80%.

2. The germanium telluride-based thermoelectric element according to claim 1, characterized by The thickness of the electrode layer is 10-2000 microns; the thickness of the barrier layer is 10-1000 microns; and the thickness of the germanium telluride-based thermoelectric layer is 0.01-200 millimeters.

3. The germanium telluride-based thermoelectric element according to claim 2, characterized by The thickness of the electrode layer is 100-1000 microns; the thickness of the barrier layer is 50-150 microns; and the thickness of the germanium telluride-based thermoelectric layer is 3-20 millimeters.

4. The germanium telluride-based thermoelectric element according to claim 1, characterized by The room temperature interfacial contact resistivity of the germanium telluride-based thermoelectric element is less than 1 μΩcm 2 The interfacial contact resistivity is the product of the sum of the contact resistance of the electrode layer and the barrier layer, the resistance of the barrier layer itself, and the contact resistance of the barrier layer and the germanium telluride-based thermoelectric layer, and the interfacial cross-sectional area.

5. The germanium telluride-based thermoelectric element according to claim 1, characterized by The electrode layer is metal or alloy.

6. The germanium telluride-based thermoelectric element according to claim 5, characterized by The electrode layer is at least one of elemental nickel, elemental copper, nickel-copper alloy, and molybdenum-copper alloy, wherein the molar percentage of copper in the nickel-copper alloy and the molybdenum-copper alloy is 20%-80%.

7. The method of producing a germanium telluride-based thermoelectric element according to any one of claims 1 to 6, characterized in that, The preparation method is one-step sintering, comprising: sequentially loading germanium telluride-based thermoelectric material, barrier layer material, and electrode layer material into a mold, and performing discharge plasma sintering or hot-press sintering in a vacuum or inert protective atmosphere to obtain the germanium telluride-based thermoelectric element; or the preparation method is high-temperature welding, comprising: sequentially loading germanium telluride-based thermoelectric layer material and barrier layer material into a mold, and performing discharge plasma sintering or hot-press sintering in a vacuum or inert protective atmosphere to obtain a sintered block; and then welding the sintered block and the electrode layer material using a solder at high temperature to obtain the germanium telluride-based thermoelectric element.

8. The production method according to claim 7, characterized by, The conditions for discharge plasma sintering are: a heating rate of 40-100℃ / min, a sintering temperature of 540-620℃, a sintering pressure of 50-70 MPa, a holding time of 5-20 min, and a cooling rate of 30-60℃ / min; and the conditions for hot-press sintering are: a heating rate of 20-80℃ / min, a sintering temperature of 570-640℃, a sintering pressure of 50-70 MPa, a holding time of 30-75 min, and a cooling rate of 20-50℃ / min.

9. The production method according to claim 7, characterized by, The welding temperature is 550-640℃, the welding pressure is 2-20 MPa, and the welding time is 5-50 min.

10. The preparation method according to claim 7, characterized in that, The solder is silver-copper alloy, wherein the molar percentage of copper is 20%-60%.

11. The preparation method according to claim 7, characterized in that, The mold is a graphite mold, a boron nitride mold, or an alloy mold.

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