A method for preparing a telluride-based thermoelectric device based on a TMDs barrier layer

Abstract

This invention provides a method for fabricating telluride-based thermoelectric devices based on TMDs (telluride-modulated metal blocks) barrier layers, specifically belonging to the field of thermoelectric device technology. This invention uses TMDs as the barrier layer for telluride thermoelectric materials, overcoming the technical bottlenecks of traditional metal barrier layers, which suffer from high modulus and cannot effectively buffer thermal stress, resulting in severe interfacial reactions. Utilizing the excellent elastic deformation capability brought by the van der Waals gaps in the layered structure of TMDs, the interfacial stress caused by the mismatch in thermal expansion coefficients between the thermoelectric material and the barrier layer is alleviated, completely avoiding the risk of interfacial cracking under high-temperature cycling. This invention selects TiTe2 and Ta... 0.5 Ti 0.5 Te2 is the optimal barrier layer for both Bi2Te3 and GeTe. After 60 days of aging tests at 523K and 773K, the interfaces of both systems remained stable. Furthermore, this invention uses TiTe2 as an intermediate layer between Bi2Te3 and GeTe, enabling one-step sintering to prepare segmented single-legged structures and effectively blocking interdiffusion of interfacial elements. Based on this design, two pairs of segmented thermoelectric modules achieve a high energy conversion efficiency of 11% at a temperature difference of 380K.

Description

Technical Field

[0001] This invention relates to a method for fabricating a telluride-based thermoelectric device based on a TMDs barrier layer, specifically belonging to the field of thermoelectric device technology. Background Technology

[0002] Thermoelectric materials enable the direct conversion of thermal energy into electrical energy and are widely used in waste heat recovery and solid-state power generation. Telluride-based thermoelectric materials (bismuth telluride, germanium telluride, etc.) exhibit excellent thermoelectric performance in the low and medium temperature range and are the core materials in this field.

[0003] However, such materials face key bottlenecks in practical applications: n-type bismuth telluride is prone to violent interfacial reactions with traditional Ni-based barrier layers above 473K; germanium telluride has poor compatibility with most metal barrier layers due to the high activity of Te and the abrupt change in the coefficient of thermal expansion; and traditional metal or alloy barrier layers have high elastic modulus (100-200GPa), which cannot buffer interfacial stress. Under medium and high temperatures, long-term service can easily lead to element interdiffusion and interfacial cracking, resulting in a sharp decline in device performance.

[0004] Therefore, developing an adaptable barrier layer that can simultaneously meet the requirements of "low contact resistance, strong diffusion suppression, and efficient stress buffering" is key to improving the reliability of telluride-based thermoelectric devices and promoting their large-scale application. Summary of the Invention

[0005] The purpose of this invention is to provide a method for fabricating telluride-based thermoelectric devices based on TMDs barrier layers, in order to solve the problems of severe interfacial reactions, stress cracking, and poor high-temperature stability of telluride thermoelectric materials.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: The invention includes: a thermoelectric material layer, which is at least one telluride thermoelectric material selected from BiTeSe, BiSbTe or GeTe;

[0007] A TMDs barrier layer is disposed at the interface of the thermoelectric material layer. The TMDs barrier layer is TiTe2 or Ta. 0.5 Ti 0.5 The elastic modulus of the Te2, TMDs barrier layer is 30-40 GPa; Among them, the thickness of the interface diffusion layer between the TMDs barrier layer and the thermoelectric material layer is ≤6nm, and after the TMDs barrier layer and the thermoelectric material layer are aged at 523K-773K for 60 days, the interface has no cracks and the element diffusion depth is low.

[0008] Furthermore, the elastic modulus of the TMDs barrier layer (30-40 GPa) is much lower than that of traditional metal barrier layers (100-200 GPa). Through the elastic deformation of the van der Waals gaps between the layers, it effectively alleviates the interfacial stress caused by the mismatch of thermal expansion coefficients. It maintains interfacial integrity even after aging for 60 days in harsh environments of 523K-773K, solving the technical bottleneck of traditional barrier layers being prone to interfacial reactions above 473K. The thickness of the interfacial diffusion layer effectively suppresses element interdiffusion, ensuring the reliability of the device during long-term service.

[0009] It also includes a solderable layer, which is disposed outside the thermoelectric material layer. The solderable layer is selected from Co, and Au or Fe is added between Co and TMDs. 90 Sb 10 One type serves as an intermediate layer to mitigate interfacial reactions; the Au foil has a thickness of 600 nm, and Fe... 90 Sb 10 The sintered thickness is 0.1 mm, and the material purity of the thermoelectric material layer is above 99.99%, with a particle size of 1-10 μm.

[0010] Furthermore, the connectors did not detach after 200 thermal cycles, ensuring the structural stability of the device under thermal stress; high purity and fine particle size ensured the consistency and performance repeatability of the thermoelectric materials; the synergistic effect of the solderable layer and the TMDs barrier layer stabilized the contact resistivity at a low level.

[0011] The thermoelectric device has a segmented structure, including GeTe-TiTe2-BiSbTe composite thermoelectric legs. In addition, TiTe2 is used as a barrier layer of n-type BiTeSe material to prepare a full bismuth telluride structure containing 7 pn junction pairs, which is encapsulated on an Al2O3 ceramic substrate.

[0012] Furthermore, the segmented structure enables an optimized combination of low- and medium-temperature materials with medium- and high-temperature materials, thus broadening the operating temperature range; through a 7-pn junction design, a conversion efficiency of 6.6% is achieved at a temperature difference of 230K, with a maximum output power of 0.38W.

[0013] The fabrication method of this telluride-based thermoelectric device based on a TMDs barrier layer includes the following steps: Step 1: Synthesize TMDs barrier layer powder, the TMDs barrier layer is TiTe2 or Ta 0.5 Ti 0.5 Te2; Step 2: The TMDs barrier layer powder and telluride thermoelectric material powder are sintered by spark plasma to form a stable joint. The sintering temperature is 673-873K, the sintering pressure is 50-80MPa, and the holding time is 5-6 minutes. Step 3: Integrate stable connectors to form a complete thermoelectric device.

[0014] Furthermore, the three-step method replaces the traditional complex process, reducing production steps and improving preparation efficiency; optimized sintering parameters ensure dense interfacial bonding and significantly reduce porosity; and the process parameters are highly controllable, making it suitable for industrial mass production.

[0015] Step 1 includes: weighing Ti powder and Te blocks or Ti powder, Ta powder and Te blocks according to the stoichiometric ratio to obtain a raw material mixture; vacuum melting the raw material mixture at 923-1273K for 10-48 hours; after melting, high-energy ball milling is performed at a ball milling speed of 1000 rpm and a ball-to-material mass ratio of 10:1.

[0016] Furthermore, vacuum melting eliminates impurities and ensures the stoichiometric accuracy of TMDs materials; high-energy ball milling obtains ultrafine powder, increasing the active surface area for sintering; and precise control of melting temperature and time yields barrier layer materials with fewer defects and higher crystallinity.

[0017] In step two, the telluride thermoelectric material powder is selected from at least one of BiTeSe, BiSbTe, or GeTe, with a purity of not less than 99.99%. Step three includes laying an intermediate layer and a solderable layer outside the thermoelectric material layer. The Co powder in the solderable layer has a particle size of 1 μm, and the gold foil is selected from commercially available gold foil with a thickness of 600 nm, suitable for making the intermediate layer between TiTe2 and Co. 90 Sb 10 It is obtained directly according to the atomic ratio, after high-energy ball milling for 10 hours, and is suitable as Ta. 0.5 Ti 0.5 The intermediate layer between Te2 and Co.

[0018] Furthermore, optimal wettability and bonding strength are provided through specific component ratios; and progressive pressure control avoids sudden stress concentration and reduces the generation of interfacial cracks; simultaneous sintering of multiple material layers is achieved, reducing interfacial contamination and performance loss.

[0019] In step three, a one-step sintering method is used to integrate GeTe, TiTe2, and BiSbTe to form a composite thermoelectric leg. The initial sintering pressure is 48 MPa, which is increased to 60 MPa during the process. The assembly of the thermoelectric device in step three includes: integrating the composite thermoelectric leg with n-type Mg3Sb... 1.5 Bi 0.5 The thermoelectric legs are connected to the Al2O3 ceramic substrate via Sn-based solder to form a pn junction structure.

[0020] Furthermore, the current density of the pn junction is optimized by using an area ratio of 0.6:1, thereby improving the conversion efficiency; the Sn-based solder exhibits stability at both low and high temperatures; and the excellent thermal conductivity of the Al2O3 substrate ensures effective heat transfer.

[0021] The thermoelectric device produced has a conversion efficiency of ≥11% at a temperature difference of 380K and a conversion efficiency of ≥6.6% at a temperature difference of 230K.

[0022] Furthermore, the 11% conversion efficiency is among the leading levels of similar segmented devices, significantly outperforming traditional devices; it maintains high efficiency under different temperature conditions, demonstrating the robustness of the technology; and it meets the diverse needs of industrial waste heat recovery and portable power generation.

[0023] The beneficial effects of this invention are: 1. By innovatively introducing low-elastic-modulus TMDs materials as the barrier layer of telluride thermoelectric materials, the core technical bottleneck of traditional metal barrier layers being unable to effectively buffer thermal stress and exhibiting severe interfacial reactions due to their high modulus is fundamentally solved; the unique van der Waals gaps of the TMDs layered structure give it excellent elastic deformation capabilities, enabling it to dynamically absorb and release interfacial stress caused by the mismatch in thermal expansion coefficients between the thermoelectric material and the barrier layer, thereby completely avoiding the risk of interfacial cracking during high-temperature cycling. Meanwhile, the stable two-phase equilibrium formed between TMDs and telluride thermoelectric materials can strongly suppress the interdiffusion of elements such as Te, Bi, and Ge, ensuring that the thickness of the interface diffusion layer can still be controlled at a low level after aging tests at harsh temperatures of 523K to 773K for up to 60 days, and that the interface reaction is weak, so that the contact resistivity is stably maintained at an excellent level of less than 5.5μΩ·cm² and 1μΩ·cm², achieving ultra-high stability for long-term device operation.

[0024] 2. At the fabrication process and device structure level, a functionally graded integration of GeTe, TiTe2 barrier layers, and BiSbTe was successfully achieved using one-step spark plasma sintering (SPS) technology, constructing a GeTe-TiTe2-BiSbTe composite thermoelectric leg. This innovative process not only significantly simplifies the cumbersome step-by-step sintering and welding process of traditional segmented devices, improving fabrication efficiency and consistency, but more importantly, it simultaneously achieves synergistic optimization of stress buffering and diffusion suppression through the TiTe2 intermediate layer, resulting in a total interfacial contact resistivity as low as 4 μΩ·cm². The final segmented thermoelectric device exhibits an energy conversion efficiency of up to 11% and an output power of 0.76 W at a temperature difference of 380 K, placing it at the forefront of the field. In addition, Co-Au and Co-Fe are designed for different application scenarios. 90 Sb 10 With multiple solderable layers and intermediate layers, a stable and reliable welding interface is formed with the TMDs barrier layer, ensuring the welding reliability and life-cycle stability of the device under various operating conditions, from low-temperature portable power generation to medium- and high-temperature industrial waste heat recovery, showing broad application prospects. Attached Figure Description

[0025] Figure 1 This is a schematic diagram comparing the elastic modulus of the TMDs barrier layer material of this invention with that of traditional metal barrier layers, polymers, alkali metals, and other materials. Figure 2 This is a schematic diagram illustrating the mechanism by which the TMDs barrier layer of this invention alleviates interfacial stress. Figure 3 This is a schematic diagram showing the relationship between the melting point and resistivity of the TMDs material of this invention; Figure 4 This is a comparison chart of the thermal expansion coefficients of the TiTe2 barrier layer of this invention and thermoelectric materials such as BiTeSe, GeTe, and SnTe at different temperatures; Figure 5 The structure Ta of this invention 0.5 Ti 0.5 Heat flow-temperature curve of Te2 barrier layer; Figure 6 This invention is Ta 0.5 Ti 0.5 Elemental line scan results of the Te2 / GeTe stable joint; Figure 7 These are high-resolution transmission electron microscope images and selected area electron diffraction patterns of the TiTe2 / BiTeSe stable joint after sintering according to the present invention. Figure 8 These are scanning electron microscope images and elemental line scan results of the connector of this invention after being vacuum aged at 523K for 60 days; Figure 9 This is a graph showing the contact resistivity test results of the connector before and after aging. Figure 10 This is a SEM characterization image of the TiTe2 / BiTeSe connector of the present invention; Figure 11 This is a graph showing the trend of conversion efficiency of the 7-pn-pair bismuth telluride thermoelectric device of the present invention as a function of operating current at different hot junction temperatures; Figure 12 This invention is Ta 0.5 Ti 0.5 High-resolution transmission electron microscope image and selected area electron diffraction pattern of the Te2 / GeTe stable connector; Figure 13 These are scanning electron microscope images and elemental line scan results of the connector of this invention after being vacuum aged at 773K for 60 days. Figure 14 This is a graph showing the contact resistivity test results of the connector before and after aging. Figure 15 This is a simulation result of the interfacial stress of the composite thermoelectric leg of the present invention during the cooling process; Figure 16This is a diagram showing the total contact resistivity of the composite thermoelectric leg of the present invention. Figure 17 This is an elemental line scan result diagram of the composite thermoelectric leg of the present invention; Figure 18 This is a graph showing the relationship between the conversion efficiency and current of the segmented thermoelectric device of this invention. Detailed Implementation

[0026] The following will be combined with the appendix Figures 1-18 The technical solutions in the embodiments are described clearly and completely.

[0027] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

[0028] Specific Implementation Method 1: Preparation of TiTe2 / BiTeSe Stable Connector; This embodiment describes a method for preparing a TiTe2 / BiTeSe stable connector, which specifically follows the following four steps: 1. In an argon atmosphere glove box with an oxygen content below 1 ppm, weigh high-purity Ti powder (99.99%) and Te blocks (99.999%) according to the stoichiometric ratio to obtain a Ti-Te raw material mixture (Ti to Te molar ratio 1:2). Place the raw material mixture in a quartz tube, evacuate the quartz tube using a vacuum pump, and seal it with a high-temperature flame. Place the sealed quartz tube containing the raw material in a muffle furnace and heat it to 923 K at a heating rate of 80 K / min-120 K / min. The mixture is kept at K for 10 hours and then cooled to room temperature in the furnace to obtain a smelted TiTe2 block. The smelted TiTe2 block is placed in a ball mill jar and sealed with stainless steel balls to obtain a ball mill jar filled with argon gas. The mass ratio of the TiTe2 block to the stainless steel balls is 1:10. In an air environment, the ball mill jar filled with argon gas is placed in a high-speed ball mill and ball milled for 10 hours at a motor speed of 1000 rpm to 1500 rpm to obtain TiTe2 barrier layer powder. 2. Select n-type BiTeSe extruded rods and grind them to prepare round blocks with a diameter of 12.7 mm to be sintered; 3. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, BiTeSe bulk and TiTe2 barrier layer powder are sequentially filled into a graphite mold with an inner diameter of 13 mm. The mass ratio of BiTeSe bulk to TiTe2 barrier layer powder is 5:1, and the thickness of BiTeSe bulk is 3 mm and the thickness of TiTe2 barrier layer powder is 0.5 mm. 4. Place the filled graphite mold in a spark plasma sintering furnace. Under vacuum, raise the temperature to 673K ​​at a heating rate of 80K / min-120K / min. Then, hold the temperature at 673K ​​and 80MPa for 5 minutes. After sintering, cool the furnace to room temperature. Cut the sintered block into strips to obtain TiTe2 / BiTeSe stable joints. The stable joints are 3mm high, 1.6mm long, and have an aspect ratio of 1:1.

[0029] By using TiTe2 as the barrier layer of BiTeSe, the elastic modulus of TiTe2 is only 38GPa, which is much lower than that of traditional metal barrier layers (100-200GPa). Its unique layered structure can dynamically buffer the interfacial stress caused by the mismatch of thermal expansion coefficients between BiTeSe and the barrier layer through the contraction and expansion of the van der Waals gaps between the layers and slight elastic sliding, thus avoiding the generation of cracks during thermal cycling and solving the problem of interfacial failure caused by stress concentration in traditional barrier layers. The TiTe2 and BiTeSe phases form a balance, effectively suppressing interdiffusion and interfacial reactions. After 60 days of vacuum aging at 523K, no interfacial cracking was observed at the joint, the element diffusion depth remained approximately the same as in the initial state, and the contact resistivity stabilized at 5.5μΩ. cm 2 The performance is far superior to traditional Ni / BiTeSe connectors. The preparation process adopts an integrated process of "vacuum melting-ball milling-discharge plasma sintering", which is simple in steps, easy to control parameters, and the joint density reaches more than 90%, with no obvious porosity defects. It can be mass-produced and provides a stable interface connection for the assembly of all-bismuth telluride thermoelectric devices.

[0030] Specific Implementation Method Two: Ta 0.5 Ti 0.5 Preparation of Te2 / GeTe stable joint The difference between this embodiment and specific embodiment one is that: Ta is prepared... 0.5 Ti 0.5 The Te2 / GeTe stabilizing connector is installed by following these four steps: 1. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, Ti powder (99.99%), Ta powder (99.88%), and Te lumps (99.999%) were weighed according to stoichiometric ratio to obtain a Ti-Ta-Te raw material mixture (Ti, Ta, and Te molar ratio 0.5:0.5:2). The raw material mixture was placed in a quartz tube, and the quartz tube was evacuated using a vacuum pump and sealed with a high-temperature flame. The sealed quartz tube containing the raw material was placed in a muffle furnace, and the temperature was raised to 1273 K at a heating rate of 80 K / min-120 K / min. The temperature was held at 1273 K for 48 hours, and then cooled to room temperature with the furnace to obtain smelted Ta. 0.5 Ti 0.5 Te2 bulk material; the smelted bulk material was densified by pre-sintering at 900K for 5 minutes using spark plasma sintering (SPS), then placed in a ball mill jar, sealed with stainless steel balls (bulk to stainless steel balls mass ratio 1:10), and ball-milled in air at a speed of 1000 rpm to 1500 rpm for 10 hours to obtain Ta. 0.5 Ti 0.5 Te2 barrier layer powder; II. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, weigh Ge powder, Te powder, and Sb powder (all with a purity ≥ 99.99%) according to stoichiometric ratio to obtain Ge. 0.9 Sb 0.1 Te raw material mixture; the raw material mixture was placed in a quartz tube, vacuum sealed, and then placed in a muffle furnace. The temperature was increased to 1273K at a rate of 80K / min-120K / min and held for 12h. Then it was slowly cooled to 873K and held for 3 days. After furnace cooling, an ingot was obtained. The ingot was ultrasonically cleaned in anhydrous ethanol for 15min, vacuum dried, and then ball-milled for 2h to pulverize to a particle size of 1-10μm to obtain Ge. 0.9 Sb 0.1 Te powder; III. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, Ge 0.9 Sb 0.1 Te powder and Ta 0.5 Ti 0.5 Te2 barrier powder was sequentially filled into a graphite mold with an inner diameter of 13mm, with a mass ratio of 5:1, and the thicknesses were 3mm and 0.5mm respectively. 4. Place the filled graphite mold in a spark plasma sintering furnace. Under vacuum, heat the mold to 673K ​​at a rate of 80K / min-120K / min. Hold the mold at 673K ​​for 5 minutes under a sintering temperature of 673K ​​and a sintering pressure of 50MPa. After sintering, allow the mold to cool to room temperature in the furnace and cut it into strips to obtain Ta. 0.5 Ti 0.5The Te2 / GeTe stabilizing connector has a height of 3mm, a length of 1.6mm, and an aspect ratio of 1:1.

[0031] Through Ta 0.5 Ti 0.5 The Te2 barrier layer exhibits excellent thermal stability, with no obvious phase transition peaks in its heat flow-temperature curve. It maintains structural stability within the GeTe service temperature range (573-773K), thus resolving the issue of poor thermal stability of TiTe2 above 673K ​​and making it suitable for medium- and high-temperature thermoelectric systems. Furthermore, the barrier layer has an elastic modulus of only 33 GPa, which can buffer the abrupt change in thermal expansion coefficient caused by the GeTe phase transition through elastic deformation. After 60 days of vacuum aging at 773 K, no interfacial reaction products were generated at the joint, element diffusion was effectively suppressed, and the contact resistivity remained below 1 μΩ. cm 2 ; Ta 0.5 Ti 0.5 Te2 and GeTe have good thermal compatibility, and their coefficients of thermal expansion fluctuate by ≤0.5×10-6K within the low-temperature rhombohedral phase range. -1 After 200 thermal cycles (RT-673K), the interface showed no cracking, providing a stable interface connection for the hot end of segmented thermoelectric devices and ensuring long-term service reliability in medium and high temperature scenarios.

[0032] Specific Implementation Method 3: Fabrication of All-Bismuth Telluride Thermoelectric Devices The difference between this embodiment and specific embodiment one is that the fabrication of the all-bismuth telluride thermoelectric device is carried out in the following three steps: 1. Prepare a TiTe2 / BiTeSe stable joint (n-type) according to the steps of Specific Implementation Method 1. The difference is that in order to enhance the solderability of TiTe2, Au foil and Co powder are laid on the outer layer, and the N-type single-leg joint is prepared by one-step sintering. II. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, Li, Bi, Sb, and Te elements (purity ≥ 99.999%) were weighed according to stoichiometric ratios to obtain Li. 0.0025 (Bi 0.4 Sb 1.6 ) 0.9975 Te 3.01 Raw material mixture; the raw material mixture was sealed in a vacuum quartz tube, heated to 1073K at 80K / min-120K / min, held for 10h, cooled with the furnace and ball-milled for 2h to obtain BiSbTe powder; then a layer of nickel was electroplated on the outer layer. III. Using Al2O3 ceramic as the upper and lower substrates of the device, eight Cu sheets (4.0mm × 1.65mm) are attached to the upper substrate, and seven Cu sheets (4.0mm × 1.65mm) are attached to the lower substrate. A pair of test pieces, consisting of one n-type thermoelectric leg and one p-type thermoelectric leg, are used, utilizing low-temperature solder (Sn... 42 Bi 58 ) and high-temperature solder (Sn5Pb) 92.5 Ag 2.5 Seven pairs of test pieces were welded onto an Al2O3 substrate to form seven pairs of pn-π type bismuth telluride thermoelectric devices. During the welding process, the low-temperature end was welded at 160℃ and left to stand for 3 minutes, while the high-temperature end was welded at 350℃ and left to stand for 3 minutes.

[0033] With a cold junction of 293K and a hot junction of 523K (a temperature difference of 230K), the device achieves a conversion efficiency of 6.6% and a maximum output power of 0.38W, which is superior to traditional BiTe-based devices (with a conventional efficiency of 5%). Furthermore, the current-voltage curve shows a good linear relationship, demonstrating good ohmic contact. Furthermore, the Co-Au solderable layer is firmly bonded to TiTe2 and bismuth telluride rods, and does not fall off after 200 thermal cycles (RT-523K), and the thermoelectric material exhibits excellent performance stability.

[0034] Specific Implementation Method 4: One-step sintering preparation of GeTe / TiTe2 / BiSbTe composite thermoelectric leg and segmented device This embodiment differs from Specific Embodiment 1 in that: the GeTe / TiTe2 / BiSbTe composite thermoelectric leg is prepared by one-step sintering and the segmented device is assembled, specifically following the six steps below: I. Prepare TiTe2 barrier layer powder according to the steps of Specific Implementation Method 1, and prepare Ge according to the steps of Specific Implementation Method 2. 0.9 Sb 0.1 Te thermoelectric powder, BiSbTe thermoelectric powder is prepared according to the steps of specific embodiment three; II. In an argon atmosphere glove box with a water and oxygen content of less than 1 ppm, according to Ge 0.9 Sb 0.1 Te powder, TiTe2 barrier layer powder, and BiSbTe powder are sequentially filled into a graphite mold with an inner diameter of 13mm. The mass ratio of the three materials is 3:1:3, and the total thickness is 5mm, of which the thickness of the TiTe2 barrier layer powder is 1mm. Co-Au solderable layer powder (thickness 0.2mm) is laid on the outside of the BiSbTe powder. 3. The graphite mold was placed in a spark plasma sintering furnace. Under vacuum conditions, the initial axial pressure was 48 MPa. The temperature was increased to 673 K at a rate of 80 K / min-120 K / min. During sintering, the pressure increased to 60 MPa. The mold was held at this temperature for 6 min and then sintered in one step. After cooling, the mold was cut into GeTe / TiTe2 / BiSbTe composite thermoelectric legs with a height of 5 mm and a cross-section of 1.6 mm × 1.6 mm. IV. Prepare Ta according to the steps of Specific Implementation Method 2 0.5 Ti 0.5 Te2 / GeTe stabilizing joint, Fe is laid on the outside of GeTe. 90 Sb 10 Solderable powder (0.25mm thick) is sintered twice at 673K ​​and 50MPa for 5 minutes to form a hot-end joint with a solderable layer. V. Using n-type Mg3Sb 1.5 Bi 0.5 The powder is used as raw material. After vacuum melting, it is ball-milled into powder, sintered at SPS873K and 60MPa for 5 minutes to densify it, and then cut into n-type thermoelectric legs of the same size as the composite thermoelectric legs (the cross-sectional area ratio of p-type to n-type thermoelectric legs is 0.6:1). 6. Two pairs of pn-pair segmented thermoelectric devices are fabricated by using Sn foil to weld the ceramic substrate and the hot end of the composite thermoelectric leg together via instantaneous liquid phase diffusion welding.

[0035] The integrated fabrication of GeTe, TiTe2, and BiSbTe is achieved through one-step sintering, eliminating the need for step-by-step sintering and additional welding. This simplifies the complex fabrication process of traditional segmented devices, reduces the number of interfaces, and lowers the risk of failure. Furthermore, the TiTe2 interlayer simultaneously achieves stress buffering and diffusion suppression, resulting in a total contact resistivity of the composite thermoelectric leg as low as 4μΩ. cm 2 This effectively reduces internal losses in the device. The segmented device achieves a conversion efficiency of 11% at a cold end of 293K and a hot end of 673K ​​(380K temperature difference), with a maximum output power of 0.76W. This is a leading level among existing segmented devices and is suitable for medium and high temperature waste heat recovery scenarios.

[0036] Example 1: Preparation and Performance Testing of TiTe2 / BiTeSe Stable Joints This embodiment prepares the TiTe2 / BiTeSe stable connector according to the steps of Specific Implementation Method 1, with the following specific parameters: The Ti-Te raw material mixture was melted at 923K and held for 10h, and ball-milled at 1200 rpm for 10h. The BiTeSe powder had a particle size of 5μm and a mass ratio of 5:1 to the TiTe2 powder. The spark plasma sintering was carried out at a heating rate of 100K / min, a sintering temperature of 673K, a pressure of 80MPa, and a holding time of 5min. The interface of the joint showed no obvious pores, and HRTEM revealed a uniform transition layer of approximately 6 nm thickness. EDS mapping showed a uniform distribution of Ti, Te, Bi, and Se elements. After aging at 523 K for 60 days, the contact resistivity was approximately 5.5 μΩ. cm 2 The joint after initial sintering (5.5μΩ) cm 2 The results were basically the same, with no significant changes; after 200 thermal cycles (RT-523K), there were no cracks at the interface, and the interface stress was relieved only by elastic deformation within the working temperature range.

[0037] like Figures 7-9 The figure shown is a microstructure and contact resistivity characterization diagram of the TiTe2 / BiTeSe joint; Figure 7 High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of the sintered TiTe2 / BiTeSe stable joint show that a thin and uniform transition layer is formed at the interface. Figure 8 The scanning electron microscope (SEM) images and elemental line scan results of the joint after 60 days of vacuum aging at 523K demonstrate that the interface structure is stable and free of cracks. Figure 9 The contact resistivity test results for the joint before and after aging show that it still maintains a resistance of 5.5 μΩ after aging. cm 2 Low contact resistance; Figure 10 The image shows the SEM characterization of the prepared TiTe2 / BiTeSe joint, verifying the tight interfacial bonding.

[0038] Example 2: Ta 0.5 Ti 0.5 Preparation and performance testing of Te2 / GeTe stable connectors This embodiment prepares Ta according to the steps of specific implementation method two. 0.5 Ti 0.5 Te2 / GeTe stable connector, specific parameters are as follows: The Ti-Ta-Te raw material mixture was smelted at 1273K for 48 hours, pre-sintered at 900K for 5 minutes, and ball-milled at 1200 rpm for 10 hours; Ge 0.9 Sb 0.1 Te powder has a particle size of 8μm, compared with Ta 0.5 Ti0.5 Te2 powder mass ratio 5:1; spark plasma sintering heating rate 100K / min, sintering temperature 673K, pressure 50MPa, holding time 5min; like Figures 5-6 As shown, this is Ta 0.5 Ti 0.5 Heat flow-temperature curve of Te2 barrier layer and Ta 0.5 Ti 0.5 Line scan diagram of interface elements of the Te2 / GeTe connector; Figure 5 For the preparation of Ta 0.5 Ti 0.5 The heat flow-temperature curve of the Te2 barrier layer reflects its excellent thermal stability with no significant phase change over a wide temperature range. Figure 6 Ta prepared in step three of Example 2 0.5 Ti 0.5 The elemental line scan results of the Te2 / GeTe stable junction show the distribution of Ge, Te, Ti and Ta elements at the interface, verifying that there are no obvious reaction products at the interface and that element diffusion is effectively suppressed. like Figures 12-14 As shown, this is Ta 0.5 Ti 0.5 Microstructure characterization diagram of Te2 / GeTe connector; Figure 12 For the preparation of Ta 0.5 Ti 0.5 High-resolution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED) patterns of the Te2 / GeTe stable connector show that a thin and uniform transition layer is formed at the interface. Figure 13 The scanning electron microscope (SEM) images and elemental line scan results of the joint after 60 days of vacuum aging at 773K demonstrate that the interface structure is stable and free of cracks. Figure 14 The results of the contact resistivity test before and after aging show that it still maintains 1μΩ after aging. cm 2 Low contact resistance.

[0039] No obvious reaction products were observed at the interface of the joint, and the element diffusion depth was ≤3nm; after aging at 773K for 60 days, the contact resistivity was <1μΩ. cm 2 The coefficient of thermal expansion is well-suited to GeTe in the rhombohedral phase. In the cubic phase, the low modulus can alleviate interfacial stress, and the interface remains intact after 200 thermal cycles.

[0040] Example 3: Fabrication and Performance Testing of All-Bismuth Telluride Thermoelectric Devices This embodiment prepares a fully bismuth telluride thermoelectric device according to the steps of Specific Implementation Method Three, with the following specific parameters: The preparation of n-type TiTe2 / BiTeSe and p-type Ni / BiSbTe joints is the same as in Example 1; the thicknesses of the Co solderable layer and Au foil are 0.1 mm and 0.01 mm, respectively; the sintering temperature is 673 K, the pressure is 50 MPa, and the holding time is 5 min; the welding uses Sn5Pb 92.5 Ag 2.5 Solder (300℃, stand for 1 min) and Sn 42 Bi 58 Solder (140℃, stand for 1 min).

[0041] Figure 11 The study demonstrates the conversion efficiency of the fabricated 7-pn-pair bismuth telluride thermoelectric devices under different hot junction temperatures (373K, 423K, 473K) as a function of operating current, showcasing the device's 6.6% conversion efficiency advantage at a temperature difference of 230K.

[0042] The test results show that the conversion efficiencies of the device at the hot junction of 373K, 423K, and 473K are 4.2%, 5.5%, and 6.6%, respectively. Example 4: Fabrication and Performance Testing of Segmented Thermoelectric Devices This embodiment prepares a segmented thermoelectric device according to the steps of Specific Implementation Method Four, such as... Figure 18 The figure shows the conversion efficiency versus current curves of the segmented thermoelectric device; it presents the conversion efficiency changes of the two pn-pair segmented devices at different hot-junction temperatures (573K, 623K, 673K), verifying the peak conversion efficiency of 11% at a temperature difference of 380K; the specific parameters are as follows: Ge 0.9 Sb 0.1 Te, TiTe2, and BiSbTe powders all have a particle size of 5-10 μm, with a three-layer mass ratio of 3:1:3; one-step sintering with an initial pressure of 48 MPa, increasing to 60 MPa during the process, a temperature of 673 K, and a holding time of 6 min; the composite thermoelectric leg dimensions are 5 mm × 1.6 mm × 1.6 mm; n-type Mg3Sb 1.5 Bi 0.5 The sintering temperature of the thermoelectric leg is 873K, the pressure is 60MPa, and the holding time is 5min. The cross-sectional area ratio of the pn type is 0.6:1. like Figures 15-17 The figure shows the interface stress simulation and elemental line scan diagram of the GeTe / TiTe2 / BiSbTe composite thermoelectric leg; Figure 15 The simulation results of the interface stress of the prepared composite thermoelectric leg during the cooling process show that the TMDs barrier layer effectively disperses stress and has no stress concentration. Figure 16 The total contact resistivity of the composite thermoelectric leg interface remained as low as ~4μΩ after aging at 523K for 60 days. cm 2 ; Figure 17 The elemental line scan results of this composite thermoelectric leg verify that GeTe and BiSbTe are effectively blocked by a TiTe2 interlayer.

[0043] The test results show that the thicknesses of the diffusion layers at the GeTe / TiTe2 and TiTe2 / BiSbTe interfaces are 2.8 nm and 3.2 nm, respectively, with a total contact resistivity of 4 μΩ. cm 2 The conversion efficiencies of the device at the hot junction of 573K, 623K, and 673K ​​are 8.2%, 9.7%, and 11%, respectively. like Figure 1 As shown, the TMDs barrier layer materials (TiTe2, Ta) used in Embodiments 1 to 4 of the present invention are illustrated. 0.5 Ti 0.5 The difference in elastic modulus distribution between Te2 and traditional metal barrier layers (Ti, FeGe2, NiGe, etc.), polymers, alkali metals and other materials intuitively presents the advantage of TMDs materials with a low elastic modulus of 30-40 GPa, providing core data support for their stress buffering performance. like Figure 2 The diagram illustrates the mechanism by which the TMDs barrier layer alleviates interfacial stress. The step-by-step demonstration of the heating-cooling cycle process clarifies the role of TiTe2 and Ta in Examples 1 to 4. 0.5 Ti 0.5 The Te2 barrier layer utilizes the contraction and expansion of the van der Waals gaps between the layers and slight elastic sliding to dynamically buffer the interfacial stress caused by the mismatch in thermal expansion coefficients between the thermoelectric material and the barrier layer, thus preventing crack formation. like Figure 3 The figure shows the relationship between the melting point and resistivity of TMDs materials; it illustrates the melting point (Tm) and resistivity (ρ) distribution of various transition metal ditellurides (TiTe2, TaTe2, MoTe2, VTe2, etc.), clarifies the suitable region of "0.4Tm < sintering temperature (Tsinter) < Tm", and verifies the properties of TiTe2 and TaTe2 in Examples 1 and 2. 0.5 Ti 0.5 The selection of Te2 as a barrier layer is reasonable and meets the requirements of sintering densification and low resistance. like Figure 4 The figure shows a comparison of the coefficient of thermal expansion (CTE) of TiTe2 with different telluride thermoelectric materials. It also shows the trend of the change of the coefficient of thermal expansion of TiTe2 barrier layer and thermoelectric materials such as BiTeSe, GeTe, and SnTe used in Examples 1, 3, and 4 at different temperatures. This visually demonstrates the thermal compatibility of TMDs barrier layer with various telluride thermoelectric materials, providing a theoretical basis for the preparation of stable joints and composite thermoelectric legs.

[0044] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments without departing from the scope of the present invention, based on the technical essence of the present invention and within the spirit and principles of the present invention, shall still fall within the protection scope of the present invention.

Claims

1. A telluride-based thermoelectric device based on a TMDs blocking layer, characterized in that, include: The thermoelectric material layer is selected from at least one telluride thermoelectric material chosen from BiTeSe, BiSbTe, or GeTe, where BiTeSe is n-type bismuth telluride and BiSbTe is p-type bismuth telluride. A TMDs barrier layer is disposed at the interface of the thermoelectric material layer. The TMDs barrier layer is TiTe2 or Ta. 0.5 Ti 0.5 The elastic modulus of the Te2, TMDs barrier layer is 30-40 GPa; Among them, the thickness of the interface diffusion layer sintered between the TMDs barrier layer and the thermoelectric material layer is ≤6nm, and after the TMDs barrier layer and the thermoelectric material layer are aged at 523K-773K for 60 days, the interface has no cracks and the element diffusion depth is low.

2. The telluride-based thermoelectric device based on a TMDs blocking layer according to claim 1, characterized in that, It also includes a solderable layer, which is disposed outside the thermoelectric material layer. The solderable layer is selected from Co, and Au or F is added between Co and TMDs. e90 Sb 10 As an intermediate layer to mitigate interfacial reactions, the gold foil thickness is 600 nm. 90 Sb 10 The sintered thickness is 0.1 mm, and the material purity of the thermoelectric material layer is above 99.99%, with a particle size of 1-10 μm.

3. The telluride-based thermoelectric device based on a TMDs blocking layer according to claim 1, characterized in that, The thermoelectric device has a segmented structure, including GeTe-TiTe2-BiSbTe composite thermoelectric legs. TiTe2 is also used as a barrier layer for n-type BiTeSe material to prepare a full bismuth telluride structure containing 7 pairs of pn junctions, which is encapsulated on an Al2O3 ceramic substrate.

4. A method for fabricating a telluride-based thermoelectric device based on a TMDs blocking layer, characterized in that, Includes the following steps: Step 1: Synthesize TMDs barrier layer powder, the TMDs barrier layer is TiTe2 or Ta 0.5 Ti 0.5 Te2; Step 2: The TMDs barrier layer powder and telluride thermoelectric material powder are sintered by spark plasma to form a stable joint. The sintering temperature is 673-873K, the sintering pressure is 50-80MPa, and the holding time is 5-6 minutes. Step 3: Integrate stable connectors to form a complete thermoelectric device, including two pairs of segmented medium-temperature devices and seven pairs of low-temperature bismuth telluride devices.

5. The preparation method according to claim 4, characterized in that, The synthesis of TMDs barrier layer powder in step one includes: weighing Ti powder and Te blocks or Ti powder, Ta powder and Te blocks according to stoichiometric ratio to obtain a raw material mixture; vacuum melting the raw material mixture at 923-1273K for 10-48 hours; after melting, high-energy ball milling is performed at a ball milling speed of 1000 rpm and a ball-to-material mass ratio of 10:

1.

6. The preparation method according to claim 4, characterized in that, In step two, the telluride thermoelectric material powder is selected from at least one of BiTeSe, BiSbTe, or GeTe, with a purity of not less than 99.99%.

7. The preparation method according to claim 4, characterized in that, Step three of the integration process involves laying an intermediate layer and a solderable layer outside the thermoelectric material layer. The Co powder in the solderable layer has a particle size of 1 μm, and the gold foil is selected with a commercial thickness of 600 nm as the intermediate layer between TiTe2 and Co. Fe 90 Sb 10 According to the atomic ratio, it was obtained after high-energy ball milling for 10 h, and used as Ta. 0.5 Ti 0.5 The intermediate layer between Te2 and Co has a sintering thickness of 0.1 mm.

8. The preparation method according to claim 4, characterized in that, In step three, a one-step sintering method is used to integrate GeTe, TiTe2 and BiSbTe to form a composite thermoelectric leg. The initial sintering pressure is 48 MPa, which is increased to 60 MPa during the process.

9. The preparation method according to claim 4, characterized in that, Step three involves assembling the two pairs of segmented thermoelectric devices, including: connecting the composite thermoelectric legs to n-type Mg3Sb. 1.5 Bi 0.5 The thermoelectric legs are connected to the ceramic substrate by Sn-based solder to form two pairs of segmented pn junction structures. The assembly of seven pairs of bismuth telluride thermoelectric devices includes connecting Ni-plated BiSbTe thermoelectric legs and sintered TiTe2 BiTeSe thermoelectric legs to a ceramic substrate using Sn-based solder to form a pn junction seven-pair segmented structure.

10. The preparation method according to claim 4, characterized in that, The two pairs of segmented medium-temperature thermoelectric devices have a conversion efficiency of ≥11% at a temperature difference of 380K, and the all-bismuth telluride low-temperature device has a conversion efficiency of ≥6.6% at a temperature difference of 230K.

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