Silver selenide-based thermoelectric element and preparation method thereof

Abstract

The invention relates to a silver selenide-based thermoelectric element and a preparation method thereof. The silver selenide-based thermoelectric element comprises a silver selenide-based material and an electrode material, wherein a metallization layer is attached to the surface of the silver selenide-based material, and the metallization layer is in electric heating connection with the electrode material through a solder layer.

Description

Technical Field

[0001] The invention belongs to the technical field of thermoelectric components, and in particular relates to a silver selenide-based thermoelectric element and a preparation method thereof. Background Art

[0002] Thermoelectric energy conversion technology is a fully static energy conversion mode that uses thermoelectric semiconductor materials to directly convert electrical energy into thermal energy. It is a green and environmentally friendly new energy technology. Thermoelectric power generation devices can directly convert waste heat into electrical energy, and have broad application prospects in industrial production and daily life; while thermoelectric cooling devices can perform the function of heat pumps and achieve fast and accurate temperature control in small areas. The output of thermoelectric power generation devices and the cooling efficiency of thermoelectric cooling devices are both determined by the intrinsic thermoelectric figure of merit of thermoelectric materials.

[0003] At present, the traditional bismuth telluride-based materials have the best thermoelectric figure of merit near room temperature. The thermoelectric figure of merit of commercial P-type materials is generally 1.1, and the thermoelectric figure of merit of N-type materials is generally around 0.9. At the same time, researchers have also discovered new semiconductor materials with high thermoelectric figures of merit, such as silver selenide-based and magnesium antimony-based. Among them, the thermoelectric figure of merit of N-type silver selenide (Ag2Se)-based materials at room temperature can reach 0.9, and the thermoelectric figure of merit at 390K can reach 1.2, which is the same as or even slightly better than N-type bismuth telluride materials. Due to higher thermoelectric performance and lower raw material costs, silver selenide-based materials should have become an effective substitute for bismuth telluride materials. However, the current research on the preparation of thermoelectric devices based on silver selenide-based materials has stagnated, especially the lack of low-impedance and high-stability connection technology between silver selenide-based thermoelectric materials and electrodes. On the one hand, the complex structure of the material itself makes it difficult to control its performance. On the other hand, since the silver selenide material exhibits a first-order phase transition near 400K in the low temperature zone, the thermal expansion coefficient in the phase transition range is large, which makes the interface structure prone to cracking.

[0004] Traditionally, the selection of electrodes for thermoelectric elements needs to follow the following criteria: 1) There is no destructive diffusion or chemical reaction between the electrode and the material matrix and the intermediate layer under the application environment and temperature conditions; 2) The thermal expansion coefficients of the thermoelectric material matrix and the electrode material and the intermediate layer should be matched as much as possible to prevent the generation of cracks in the interface structure, hinder the transmission of energy, and ultimately lead to interface failure; 3) The interface structure needs to exhibit low contact thermal resistance and contact resistance to reduce temperature difference loss and energy loss. The high performance temperature range of silver selenide-based materials is concentrated near room temperature, so its operating temperature is basically below 500K, and generally no element diffusion and serious chemical reactions at high temperatures will occur. However, silver selenide material undergoes a phase change at 400K, and the low-temperature phase is an orthorhombic structure with a thermal expansion coefficient of 27.5×10 -6 K -1 After the phase transition, it becomes a body-centered cubic structure with a thermal expansion coefficient of 34.3×10 -6K -1 In the narrow phase transition temperature range around 400K, the volume change of silver selenide material is obvious, and the thermal expansion coefficient can reach 100×10 -6 K -1 For conventional electrode materials for thermoelectric elements, such as copper, the thermal expansion coefficient is about 16.5×10 -6 K -1 , which is quite different from silver selenide-based materials. This leads to the easy generation of interface cracks and failures in the conventional thermoelectric element welding process, which is usually manifested as extremely large interface contact resistance, making it difficult to prepare traditional out-of-plane thermoelectric devices with practical application significance. All the silver selenide-based thermoelectric devices reported so far are in-plane thin-film devices, which use Ag paste, carbon paste and other conductive pastes to electrically connect the silver selenide thin film material and the electrode material. The device has a large internal resistance, a still high contact resistance, and a structure limited to special application scenarios, making it difficult to achieve widespread thermoelectric power generation / refrigeration applications.

[0005] Therefore, there is an urgent need in this field to develop a reliable method for preparing silver selenide-based thermoelectric elements to alleviate the thermal expansion coefficient mismatch problem between silver selenide-based materials and electrode materials, while obtaining an interface with lower contact impedance, and expanding the structure of silver selenide-based thermoelectric devices from thin film form to all topological structures, thereby realizing the widespread preparation of thermoelectric elements based on silver selenide-based materials. Summary of the invention

[0006] In view of the above technical problems, the present invention aims to provide a silver selenide-based thermoelectric element with good interface bonding and low contact impedance and a preparation method thereof.

[0007] In a first aspect, the present invention provides a silver selenide-based thermoelectric element, which comprises: a silver selenide-based material and an electrode material; wherein a metallization layer is attached to the surface of the silver selenide-based material, and the metallization layer and the electrode material are electrically and thermally connected via a solder layer.

[0008] Preferably, the silver selenide-based material is n-type Ag2Se, or an n-type Ag2Se-based compound prepared by doping, solid solution or composite method with n-type Ag2Se as the matrix; Wherein, the chemical formula of the silver selenide-based material is Ag2Se, Ag 2±x M x Se 1±y N y or Ag 2±x M x Se 1±y N y +H, 0≤x≤1, 0≤y≤0.5; M and N are elements doped or dissolved in the Ag site and Se site of n-type Ag2Se, respectively, and H is a second phase material composited with n-type Ag2Se.

[0009] Preferably, the M is Ag, Au, Cu, Sn, the N is S, Se, Te, Cl, Br, I, the H is CNT, CuAgSe, Te, AgSbSe2, AgAl; preferably, the silver selenide-based material is Ag2Se, Ag2Se 1.06 、Ag2Se 0.9 S 0.1 .

[0010] Preferably, the metallization layer is composed of at least two metals arranged in sequence, preferably three metals arranged in sequence; wherein the metal constituting the metallization layer is selected from Mo, Cu, Sn, Au, Ag, W, Nb, In, Ni, and Al.

[0011] Preferably, the first layer of metal in contact with the silver selenide-based material is selected from one of Au, Mo, W, and Nb, the second layer of metal in contact with the first layer of metal is selected from one of Cu and Sn, and the third layer of metal in contact with the second layer of metal is selected from one of Cu and Sn; preferably, the metals of the metallization layer are Au-Cu-Sn, Mo-Cu-Sn, W-Sn, and Nb-Cu in order.

[0012] Preferably, the thickness of each metal layer of the metallization layer is 0.001-100 μm, preferably 0.05-5 μm.

[0013] Preferably, the solder component of the solder layer is Bi-In, Bi-In-Sn, Bi-Sn, Sb-Sn, Bi-Ag-Sn, Ag-Cu-Sn, Pb-Sn, In, Sn, Ag paste or carbon paste, and the welding temperature range is 50 to 500°C; preferably, the component of the solder layer is Bi-In-Sn component, and the welding temperature is 90°C.

[0014] Preferably, the electrode material includes Cu, Au, Pt, Ti and alloys thereof, preferably Cu and alloys thereof.

[0015] In a second aspect, the present invention provides a method for preparing the above-mentioned silver selenide-based thermoelectric element, the preparation method comprising the following steps: First, the silver selenide-based material is pretreated and various layers of metal are sequentially prepared on the surface thereof to form a metallization layer, thereby achieving the bonding of the metallization layer with the surface of the silver selenide-based material; Then, the silver selenide-based material with a metallization layer attached to the surface is heated to a soldering temperature so that the solder melts and covers the metallization layer; Next, the electrode material is placed on the molten solder, and the temperature is lowered to achieve electrical and thermal connection between the metallization layer and the electrode material through the solder, thereby obtaining the silver selenide-based thermoelectric element.

[0016] Preferably, the metal layers of the metallization layer are prepared in sequence by magnetron sputtering, evaporation, electroplating, chemical plating or spraying, preferably by magnetron sputtering; The background vacuum degree of the magnetron sputtering method is 10 -2 ~10 -4 Pa, preferably 10 -3 Pa; the heating temperature is room temperature to 350°C, preferably 50°C; the sputtering atmosphere is Ar; the sputtering pressure is 0.1 to 2.5 Pa; the sputtering power is 70W to 5KW, preferably 100W to 5KW; and the sputtering time is 1min to 5h.

[0017] Beneficial Effects The present invention fills the gap in the current lack of silver selenide-based thermoelectric element preparation technology. The present invention provides a thermoelectric element structure prepared by magnetron sputtering and other methods, wherein at least two metallization layers are sequentially attached to the surface of a silver selenide-based material, and then electrically and thermally connected with conventional solder and electrode materials; The metallized layer prepared by the present invention and the silver selenide-based thermoelectric element composed of the metallized layer can alleviate the interface failure phenomenon caused by the thermal expansion coefficient problem of the silver selenide-based material, and present a lower interface contact impedance, so that the silver selenide-based material with high thermoelectric performance near room temperature can be promoted to practical application, and thermoelectric power generation and refrigeration devices near room temperature can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the interface structure of the silver selenide-based thermoelectric element provided by the present invention; wherein the first metal layer 2 is attached to the surface of the silver selenide-based material 1, the second metal layer 3 is attached to the surface of the first metal layer 2, the metal layer 4 represents one or more metal layers attached to the surface of the second metal layer 3 in sequence, the metal layers 2-4 form a metallization layer, and the solder layer 5 is attached to the surface of the outermost metal layer and directly contacts the surface of the electrode material 6; Figure 2 The scanning electron microscope image of the Au-Cu-Sn structure metallization layer prepared in Example 1 and the silver selenide-based thermoelectric element composed thereof; Figure 3 A schematic diagram of the contact resistance variation relationship of the Au-Cu-Sn structure metallization layer prepared in Example 1 and the silver selenide-based thermoelectric element composed thereof; Figure 4 A schematic diagram of the contact resistance variation relationship of the Mo-Cu-Sn structure metallization layer prepared in Example 2 and the silver selenide-based thermoelectric element composed thereof; Figure 5 A schematic diagram of the contact resistance variation relationship of the W-Sn structure metallization layer prepared in Example 3 and the silver selenide-based thermoelectric element composed thereof; Figure 6A schematic diagram of the contact resistance variation relationship of the Nb-Cu structure metallization layer prepared in Example 4 and the silver selenide-based thermoelectric element composed thereof; Figure 7 A schematic diagram of the contact resistance variation relationship of the W-Au structure metallization layer prepared in Comparative Example 1 and the silver selenide-based thermoelectric element composed thereof; Figure 8 Schematic diagram of the contact resistance change relationship of the Ag-Cu-Sn structure metallization layer prepared in Comparative Example 2 and the silver selenide-based thermoelectric element composed of it. DETAILED DESCRIPTION

[0019] The present invention is further described by way of embodiments. It should be understood that the following embodiments are only used to illustrate the present invention, rather than to limit the present invention.

[0020] The present invention selects at least two metals and sequentially attaches them to the surface of a silver selenide-based material that has been roughened and cleaned by magnetron sputtering or other techniques, thereby obtaining a metallization layer that is well bonded to the silver selenide-based material, and then uses solder to electrically and thermally connect it to an electrode material, ultimately obtaining a silver selenide-based thermoelectric element that has no cracking when cut and has low interface contact resistance.

[0021] First, the present invention provides a silver selenide-based thermoelectric element. Figure 1 As shown, the silver selenide-based thermoelectric element includes: a silver selenide-based material and an electrode material; wherein a metallization layer is attached to the surface of the silver selenide-based material, and the metallization layer and the electrode material are electrically and thermally connected via a solder layer.

[0022] In some embodiments, the silver selenide-based material can be n-type Ag2Se, or an n-type Ag2Se-based compound prepared by doping, solid solution or composite method with n-type Ag2Se as the matrix. Unlike p-type thermoelectric materials with a use temperature range in the medium temperature range, the silver selenide used in the present invention belongs to an n-type thermoelectric material with a use temperature range in the low temperature range near room temperature.

[0023] Wherein, the chemical formula of the silver selenide-based material can be Ag2Se, Ag 2±x M x Se 1±y N y or Ag 2±x M x Se 1±y N y +H, 0≤x≤1, 0≤y≤0.5; wherein M and N are elements doped or dissolved in the Ag and Se sites of n-type Ag2Se, respectively, and H is a second phase material composited with n-type Ag2Se.

[0024] Preferably, the M may be Ag, Au, Cu, Sn, the N may be S, Se, Te, Cl, Br, I, and the H may be CNT (carbon nanotube), CuAgSe, Te, AgSbSe2, AgAl. As an example, the silver selenide-based material may be Ag2Se, Ag2Se 1.06 (M=Ag, N=Se, x=0, y=0.06), Ag2Se 0.9 S 0.1 (M=Ag, N=S, x=0, y=0.1).

[0025] The silver selenide-based material used in the present invention can be prepared by itself or purchased commercially. As an example, (1) the preparation process of the Ag2Se can be: the raw material single substance is placed in a quartz tube according to the stoichiometric ratio, the tube is vacuum sealed and the temperature is raised to 1000°C for melting reaction, and then the temperature is lowered to obtain an ingot, the ingot is crushed and subjected to discharge plasma sintering, and the sintering conditions are 250°C+50Mpa+5min to obtain the Ag2Se material. (2) The Ag 2±x M x Se 1±y N y The preparation process can be: the raw materials are placed in a quartz tube according to the stoichiometric ratio, the tube is vacuum sealed and the temperature is raised to 1000°C for melting reaction, and then the temperature is lowered to obtain an ingot, the ingot is crushed into powder and hot-pressed sintered at a sintering condition of 300°C + 30Mpa + 10min to obtain the Ag 2±x M x Se 1±y N y Materials. (3) The Ag 2±x M x Se 1±y N y The preparation process of +H can be: 2±x M x Se 1±y N y The raw material ingot was crushed into powder and mixed with the second phase H according to the stoichiometric ratio and placed in a ball mill. After ball milling for 4 hours, a uniformly mixed Ag was obtained. 2±x M x Se 1±y N y +H composite powder, and then hot-press sintering the powder under the sintering conditions of 300°C+30Mpa+10min to obtain the Ag 2±x M x Se 1±y N y +H material.

[0026] In some embodiments, the metallization layer is composed of at least two metals arranged in sequence, preferably three metals arranged in sequence, such a structure can play a role in reducing contact impedance and alleviating interface cracking. Wherein, the metal constituting the metallization layer can be selected from Mo, Cu, Sn, Au, Ag, W, Nb, In, Ni, Al. The selection of the silver selenide-based material metallization layer needs to ensure low impedance, good bonding between the silver selenide material and the electrode, and wettability with the solder. By adopting the above-mentioned type of metallization layer suitable for silver selenide-based materials, the successful preparation of silver selenide-based thermoelectric elements can be completed.

[0027] Preferably, the first layer of metal in contact with the silver selenide-based material is selected from one of Au, Mo, W, and Nb, the second layer of metal in contact with the first layer of metal is selected from one of Cu and Sn, and the third layer of metal in contact with the second layer of metal is selected from one of Cu and Sn; more preferably, the metals of the metallization layer can be Au-Cu-Sn, Mo-Cu-Sn, W-Sn, and Nb-Cu in sequence. The metallization layer combination adopted by the present invention can produce lower contact impedance with the silver selenide matrix, and can effectively relieve interface stress and prevent interface cracking, while showing good wettability and bonding with solder. In the multi-layer metal of the present invention, the first layer of metal is mainly used to reduce interface impedance, and the remaining metal layers are mainly used to relieve stress at the connection interface between the silver selenide-based material and the electrode, and increase solderability.

[0028] In some embodiments, the thickness of each metal layer of the metallization layer may be 0.001 to 100 μm, preferably 0.05 to 5 μm. If the thickness is too large, the internal resistance of the metal layer will increase, resulting in reduced output performance of the component; if the thickness is too small, the adhesion of the metallization layer to the substrate surface will be reduced.

[0029] The solder composition of the solder layer can be conventional solder. In some embodiments, the component of the solder layer can be Bi-In, Bi-In-Sn, Bi-Sn, Sb-Sn, Bi-Ag-Sn, Ag-Cu-Sn, Pb-Sn, In, Sn, Ag paste or carbon paste, and the welding temperature range can be 50 to 500°C; preferably, the component of the solder layer is a commercial Bi-In-Sn component, and the welding temperature is 90°C.

[0030] In some embodiments, the solder layer may have a thickness of 0.06-5 μm.

[0031] In some embodiments, the electrode material may include Cu, Au, Pt, Ti and alloys thereof, preferably Cu and alloys thereof.

[0032] By using solder to electrically connect the metallization layer to the electrode material, low impedance and high stability of the electric heating element can be ensured. In some embodiments, the interface contact resistivity between the silver selenide-based material and the electrode material in the silver selenide-based thermoelectric element is 2-8 μΩcm 2 The contact resistivity is the core indicator of the interface contact impedance, which is generally less than 20μΩcm 2 It is generally believed that the interface contact impedance is small. The thermal expansion coefficient of silver selenide-based materials at room temperature is 27.5×10 - 6 K -1 The thermal expansion coefficient of copper electrode material is about 16.5×10 -6 K -1 .

[0033] In some embodiments, Au-Cu-Sn structure is used as the metallization layer, Bi-In-Sn component is used as solder, and the interface contact resistivity between the silver selenide-based material and the Cu electrode in the component is 2.1 μΩcm 2 Using Mo-Cu-Sn structure as metallization layer and Bi-In-Sn component as solder, the interface contact resistivity between silver selenide-based material and Cu electrode in the component is 4μΩcm 2 and 5μΩcm 2 Using W-Sn structure as metallization layer and Bi-In component as solder, the interface contact resistivity between silver selenide-based material and Cu electrode in the component is 6.7μΩcm 2 and 7.2μΩcm 2 Using Nb-Cu structure as metallization layer and In component as solder, the interface contact resistivity between silver selenide-based material and Cu electrode in the component is 2.7μΩcm 2 .

[0034] The silver selenide-based thermoelectric element provided by the present invention has good interface bonding, does not break after cutting, and has low contact resistivity. It can be used to prepare thermoelectric devices of almost all structures, including surface-type thermoelectric devices with practical application significance, to achieve thermoelectric power generation and refrigeration functions, and is suitable for long-term use in a temperature range near room temperature.

[0035] The following is an exemplary description of the preparation method of the silver selenide-based thermoelectric element provided by the present invention. The preparation method may include the following steps: first, pre-treating the silver selenide-based material and sequentially preparing various layers of metal on its surface to form a metallization layer, so as to achieve the combination of the metallization layer and the surface of the silver selenide-based material; then, heating the silver selenide-based material with the metallization layer attached to the surface to the welding temperature so that the solder melts and covers the metallization layer; then, placing the electrode material on the molten solder, cooling it down to achieve the electric and thermal connection between the metallization layer and the electrode material through the solder, and obtaining the silver selenide-based thermoelectric element.

[0036] In some embodiments, the pretreatment process includes roughening and cleaning the surface of the silver selenide-based material.

[0037] The roughening can be performed by grinding, sandblasting or chemical reagent corrosion, and the roughness of the surface of the silver selenide-based material can be controlled to be 300-1000nm; preferably, the surface roughening of the silver selenide-based material adopts a sandblasting process, and the corundum sand used in the sandblasting process has a particle size of 220 mesh and an air pressure of 0.05MPa. The adhesion between the metallization layer and the substrate can be increased by roughening, and the roughness is controlled within the above-mentioned specific range, which can not only ensure the adhesion, but also save the preparation thickness of the metallization layer.

[0038] Wherein, the cleaning can use a deionized water ultrasonic method.

[0039] In some embodiments, each metal layer of the metallization layer can be prepared in sequence by magnetron sputtering, evaporation, electroplating, chemical plating or spraying, preferably magnetron sputtering. The thickness of the metallization layer can be controlled by adjusting the sputtering power and / or sputtering time.

[0040] The background vacuum of the magnetron sputtering method can be 10 -2 ~10 -4 Pa, preferably 10 -3 Pa; the heating temperature can be room temperature to 350°C, preferably 50°C; the sputtering atmosphere can be Ar; the sputtering pressure can be 0.1 to 2.5 Pa; the sputtering power can be 70W to 5KW, preferably 100W to 5KW; the sputtering time can be 1min to 5h. By controlling the process parameters such as the sputtering pressure, sputtering power and sputtering time, the thickness of the prepared metal layer can be ensured to be within the optimal range.

[0041] In some embodiments, the rate at which the molten solder is cooled may be 1-30° C. / min.

[0042] The process of the present invention is simple, and the obtained silver selenide-based thermoelectric element has high interface performance and reliability, filling the gap in the current lack of silver selenide-based thermoelectric element preparation technology. The present invention provides a thermoelectric element structure formed by at least two metal layers sequentially attached to the surface of a silver selenide-based material by a method such as magnetron sputtering, and then electrically and thermally connected with solder and electrode materials. Among them, the metallized layer and the silver selenide-based thermoelectric element composed of the metallized layer can alleviate the interface failure phenomenon caused by the problem of the thermal expansion coefficient of the silver selenide-based material, and present a lower interface contact impedance, which can promote the silver selenide-based material with high thermoelectric performance near room temperature to practical applications, and prepare thermoelectric power generation and refrigeration devices near room temperature.

[0043] The following examples are further listed to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples in a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0044] Example 1

[0045] The method for preparing the silver selenide-based thermoelectric element provided in this embodiment comprises the following steps: (1) Take Ag2Se obtained by spark plasma sintering 1.06 The material (diameter 10 mm, thickness 2 mm) was roughened by sandblasting, wherein 220 mesh corundum sand and 0.05 MPa air pressure were used in the sandblasting process. After sandblasting, the material was cleaned and dried and then fixed on the base of magnetron sputtering; (2) Pump the sputtering chamber vacuum to 10 -3 Pa, high-purity Ar was introduced, and the Au target was sputtered at a power of 200 W under a pressure of 0.8 Pa, the sputtering time was 10 min, and the sputtering thickness was 60 nm. Then, the Cu target was sputtered at a power of 200 W, the sputtering time was 3 h, and the sputtering thickness was 5 μm. Then, the Sn target was sputtered at a power of 200 W, the sputtering time was 40 min, and the sputtering thickness was 2 μm, to form an Au-Cu-Sn metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 90°C, apply a flux such as hydrogenated rosin on the surface of the sample, and then place Bi-In-Sn solder until the melted solder completely covers the surface of the metallization layer. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a sample with a size of approximately 4×4×4.5 mm. 3 Silver selenide-based thermoelectric elements.

[0046] Figure 2 The scanning electron microscope image of the Au-Cu-Sn structure metallization layer and the silver selenide-based thermoelectric element composed of it prepared in Example 1. It can be seen from the figure that the metallization layer and the Cu electrode, Ag2Se 1.06 The interfaces between materials are well bonded without interface cracks and diffusion.

[0047] The interface contact resistivity of the Ag2Se-based thermoelectric element prepared in this Example 1 was measured by a four-probe method. Figure 3The schematic diagram of the contact resistance change relationship of the Au-Cu-Sn structure metallization layer and the silver selenide-based thermoelectric element composed of it prepared in Example 1. It can be seen from the figure that the interface contact resistivity value of the Ag2Se-based thermoelectric element prepared in Example 1 is 2.1μΩcm 2 , indicating that the component interface contact is good.

[0048] Example 2

[0049] The method for preparing the silver selenide-based thermoelectric element provided in this embodiment comprises the following steps: (1) Take Ag2Se obtained by spark plasma sintering 1.06 The material (diameter 10mm, thickness 2mm) was polished with 400#, 600#, 800#, and 1000# sandpaper in turn. After polishing, the material was cleaned and dried and then fixed on the base of magnetron sputtering. (2) Pump the sputtering chamber vacuum to 10 -3 Pa, high-purity Ar was introduced, and the Mo target was sputtered at a power of 200 W under a pressure of 0.8 Pa, the sputtering time was 50 min, and the sputtering thickness was 1 μm. Then, the Cu target was sputtered at a power of 200 W, the sputtering time was 1 h, and the sputtering thickness was 2 μm. Then, the Sn target was sputtered at a power of 200 W, the sputtering time was 40 min, and the sputtering thickness was 2 μm, to form a Mo-Cu-Sn metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 90°C, apply a flux such as hydrogenated rosin on the surface of the sample, and then place Bi-In-Sn solder until the melted solder completely covers the surface of the material. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a size of approximately 4×4×4.5 mm. 3 Silver selenide-based thermoelectric elements.

[0050] The interface contact resistivity of the two Ag2Se-based thermoelectric elements prepared in this embodiment was measured by a four-probe method. Figure 4 The schematic diagram of the contact resistance variation relationship of the Mo-Cu-Sn structure metallization layer and the silver selenide-based thermoelectric element composed of it prepared in Example 2. It can be seen from the figure that the interface contact resistivity value of the two Ag2Se-based thermoelectric elements is 4μΩcm 2 and 5μΩcm 2 , indicating that the component interface contact is good.

[0051] Example 3

[0052] The method for preparing the silver selenide-based thermoelectric element provided in this embodiment comprises the following steps: (1) The Ag2Se material (diameter 10 mm, thickness 2 mm) obtained by spark plasma sintering was taken, and its surface was roughened by sandblasting, wherein 220 mesh corundum sand and 0.05 MPa air pressure were used in the sandblasting process. After sandblasting, the material was cleaned and dried and then fixed on the base of magnetron sputtering; (2) Pump the sputtering chamber vacuum to 10 -3 Pa, high-purity Ar was introduced, and W target was sputtered at 200W power under 0.8Pa pressure, the sputtering time was 1h, the sputtering thickness was 1μm, and then Sn target was sputtered at 70W power, the sputtering time was 40min, the sputtering thickness was 1μm, to form a W-Sn metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 120°C, apply a flux such as hydrogenated rosin on the surface of the sample, and then place Bi-In solder until the melted solder completely covers the surface of the metallization layer. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a size of approximately 4×4×4.5 mm. 3 Silver selenide-based thermoelectric elements.

[0053] The interface contact resistivity of the two Ag2Se-based thermoelectric elements prepared in this embodiment was measured by a four-probe method. Figure 5 The schematic diagram of the contact resistance variation relationship of the W-Sn structure metallization layer and the silver selenide-based thermoelectric element composed thereof prepared in Example 3. It can be seen from the figure that the interface contact resistivity value of the two Ag2Se-based thermoelectric elements prepared in this example is 6.7μΩcm 2 and 7.2μΩcm 2 , indicating that the component interface contact is good.

[0054] Example 4

[0055] The method for preparing the silver selenide-based thermoelectric element provided in this embodiment comprises the following steps: (1) Take Ag2Se obtained by spark plasma sintering 0.9 S 0.1 The material (size is 10 mm in diameter and 2 mm in thickness) was roughened by sandblasting, wherein 220 mesh corundum sand and 0.05 MPa air pressure were used in the sandblasting process. After sandblasting, the material was cleaned and dried and then fixed on the base of magnetron sputtering; (2) Pump the sputtering chamber vacuum to 10 -3Pa, high-purity Ar was introduced, and the Nb target was sputtered at a power of 200 W under a pressure of 0.8 Pa, the sputtering time was 1 h, and the sputtering thickness was 1 μm. Then, the Cu target was sputtered at a power of 200 W, the sputtering time was 1 h, and the sputtering thickness was 2 μm, to form a Nb-Cu metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 180°C and place In solder on the surface of the sample until the melted solder completely covers the surface of the metallization layer. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a sample with a size of approximately 4×4×4.5 mm. 3 Silver selenide-based thermoelectric elements.

[0056] The interface contact resistivity of the Ag2Se-based thermoelectric element prepared in this embodiment was measured by a four-probe method. Figure 6 The schematic diagram of the contact resistance variation of the Nb-Cu structure metallization layer and the silver selenide-based thermoelectric element composed of the Nb-Cu structure metallization layer prepared in Example 4. It can be seen from the figure that the interface contact resistivity value of the Ag2Se-based thermoelectric element prepared in this example is 2.7μΩcm 2 , indicating that the component interface contact is good.

[0057] It can be seen from the above-mentioned multiple embodiments that the Ag2Se-based thermoelectric element prepared by the present invention has good interface bonding and low contact impedance, which can meet the actual use requirements of the Ag2Se-based thermoelectric element near room temperature.

[0058] Comparative Example 1

[0059] The preparation method of the silver selenide-based thermoelectric element provided in this comparative example comprises the following steps: (1) Take Ag2Se obtained by spark plasma sintering 1.02 The material (diameter 10 mm, thickness 2 mm) was roughened by sandblasting, wherein 220 mesh corundum sand and 0.05 MPa air pressure were used in the sandblasting process. After sandblasting, the material was cleaned and dried and then fixed on the base of magnetron sputtering; (2) Pump the sputtering chamber vacuum to 10 -3 Pa, high-purity Ar was introduced, and W target was sputtered at 200W power under 0.8Pa pressure, the sputtering time was 40min, the sputtering thickness was 0.8μm, and then Au target was sputtered at 200W power, the sputtering time was 30min, the sputtering thickness was 180nm, to form a W-Au metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 90°C, apply a flux such as hydrogenated rosin on the surface of the sample, and then place Bi-In-Sn solder until the melted solder completely covers the surface of the metallization layer. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a size of approximately 4×4×4.5 mm. 3 Silver selenide-based thermoelectric elements.

[0060] The interface contact resistivity of the two Ag2Se-based thermoelectric elements prepared in this embodiment was measured by a four-probe method. Figure 7 The schematic diagram of the contact resistance variation relationship of the W-Au structure metallization layer and the silver selenide-based thermoelectric element composed of it prepared in comparative example 1. It can be seen from the figure that the interface contact resistivity value of the two Ag2Se-based thermoelectric elements prepared in this example is 209μΩcm 2 and 197μΩcm 2 , indicating that the interface contact of the component is poor and the type of metallization layer needs to be adjusted.

[0061] Comparative Example 2

[0062] The preparation method of the silver selenide-based thermoelectric element provided in this comparative example comprises the following steps: (1) Take Ag2Se obtained by spark plasma sintering 1.06 The material (diameter 10 mm, thickness 2 mm) was roughened by sandblasting, wherein 220 mesh corundum sand and 0.05 MPa air pressure were used in the sandblasting process. After sandblasting, the material was cleaned and dried and then fixed on the base of magnetron sputtering; (2) Pump the sputtering chamber vacuum to 10 -3 Pa, high-purity Ar was introduced, and Ag target was sputtered at 200W power under 0.8Pa pressure, the sputtering time was 30min, the sputtering thickness was 200nm, then Cu target was sputtered at 200W power, the sputtering time was 3h, the sputtering thickness was 5μm, and then Sn target was sputtered at 200W power, the sputtering time was 40min, the sputtering thickness was 2μm, to form Ag-Cu-Sn metallization layer; (3) After sputtering, take out the sample and place it on a hot plate. Raise the temperature of the hot plate to 90°C, apply a flux such as hydrogenated rosin on the surface of the sample, and then place Bi-In-Sn solder until the melted solder completely covers the surface of the metallization layer. (4) Then, a copper block with a clean surface was placed on the molten solder. The size of the copper block was 10 mm in diameter and 2 mm in thickness. After cooling, the sample was cut using the wire cutting method to obtain a size of approximately 4×4×4.5 mm. 3Silver selenide-based thermoelectric elements.

[0063] The interface contact resistivity of the two Ag2Se-based thermoelectric elements prepared in this embodiment was measured by a four-probe method. Figure 8 The schematic diagram of the contact resistance change relationship of the Ag-Cu-Sn structure metallization layer and the silver selenide-based thermoelectric element composed of it prepared in Comparative Example 2. It can be seen from the figure that the interface contact resistivity value of the Ag2Se-based thermoelectric element prepared in this example is 628μΩcm 2 This indicates that the interface contact of the component is poor, and the selection of Ag target and sputtering process need to be further adjusted.

[0064] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A silver selenide-based thermoelectric element, characterized in that: The silver selenide-based thermoelectric element comprises: a silver selenide-based material and an electrode material; wherein a metallization layer is attached to the surface of the silver selenide-based material, and the metallization layer and the electrode material are electrically and thermally connected via a solder layer.

2. The silver selenide-based thermoelectric element according to claim 1, characterized in that: The silver selenide-based material is n-type Ag2Se, or an n-type Ag2Se-based compound prepared by doping, solid solution or composite method with n-type Ag2Se as the matrix; wherein the chemical formula of the silver selenide-based material is Ag2Se, Ag 2±x M x Se 1±y N y or Ag 2±x M x Se 1±y N y +H, 0≤x≤1, 0≤y≤0.5; M and N are elements doped or dissolved in the Ag site and Se site of n-type Ag2Se, respectively, and H is a second phase material composited with n-type Ag2Se.

3. The silver selenide-based thermoelectric element according to claim 1 or 2, characterized in that: The M is Ag, Au, Cu, Sn, the N is S, Se, Te, Cl, Br, I, and the H is CNT, CuAgSe, Te, AgSbSe2, AgAl; preferably, the silver selenide-based material is Ag2Se, Ag2Se 1.06 、Ag2Se 0.9 S 0.1 .

4. The silver selenide-based thermoelectric element according to any one of claims 1 to 3, characterized in that: The metallization layer is composed of at least two metals arranged in sequence, preferably three metals arranged in sequence; wherein the metal constituting the metallization layer is selected from Mo, Cu, Sn, Au, Ag, W, Nb, In, Ni, and Al.

5. The silver selenide-based thermoelectric element according to any one of claims 1 to 4, characterized in that: The first layer of metal in contact with the silver selenide-based material is selected from one of Au, Mo, W, and Nb, the second layer of metal in contact with the first layer of metal is selected from one of Cu and Sn, and the third layer of metal in contact with the second layer of metal is selected from one of Cu and Sn; preferably, the metals of the metallization layer are Au-Cu-Sn, Mo-Cu-Sn, W-Sn, and Nb-Cu in order.

6. The silver selenide-based thermoelectric element according to any one of claims 1 to 5, characterized in that: The thickness of each metal layer of the metallization layer is 0.001-100 μm, preferably 0.05-5 μm.

7. The silver selenide-based thermoelectric element according to any one of claims 1 to 6, characterized in that: The solder component of the solder layer is Bi-In, Bi-In-Sn, Bi-Sn, Sb-Sn, Bi-Ag-Sn, Ag-Cu-Sn, Pb-Sn, In, Sn, Ag paste or carbon paste, and the welding temperature range is 50 to 500°C; preferably, the component of the solder layer is Bi-In-Sn component, and the welding temperature is 90°C.

8. The silver selenide-based thermoelectric element according to any one of claims 1 to 7, characterized in that: The electrode material includes Cu, Au, Pt, Ti and alloys thereof, preferably Cu and alloys thereof.

9. A method for preparing the silver selenide-based thermoelectric element according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: First, the silver selenide-based material is pretreated and various layers of metal are sequentially prepared on the surface thereof to form a metallization layer, thereby achieving the bonding of the metallization layer with the surface of the silver selenide-based material; Then, the silver selenide-based material with a metallization layer attached to the surface is heated to a soldering temperature so that the solder melts and covers the metallization layer; Next, the electrode material is placed on the molten solder and the temperature is lowered to achieve electrical and thermal connection between the metallization layer and the electrode material through the solder, thereby obtaining the silver selenide-based thermoelectric element.

10. The preparation method according to claim 9, characterized in that: The metal layers of the metallization layer are sequentially prepared by magnetron sputtering, evaporation, electroplating, chemical plating or spraying, preferably by magnetron sputtering; The background vacuum degree of the magnetron sputtering method is 10 -2 ~10 -4 Pa, preferably 10 -3 Pa; the heating temperature is room temperature to 350°C, preferably 50°C; the sputtering atmosphere is Ar; the sputtering pressure is 0.1 to 2.5 Pa; the sputtering power is 70W to 5KW, preferably 100W to 5KW; and the sputtering time is 1min to 5h.

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