SnTe-based thermoelectric material and preparation method thereof

Abstract

The application discloses a SnTe-based thermoelectric material and a preparation method thereof, and belongs to the technical field of thermoelectricity. The application adopts high-purity metal elements as raw materials, and the raw materials are mixed according to a stoichiometric ratio, and then a cast ingot is obtained through a melting reaction after vacuum packaging. Subsequently, the cast ingot is subjected to high-temperature annealing treatment. After the cast ingot subjected to the high-temperature annealing treatment is ground into powder, a dense block-shaped SnTe-based thermoelectric material is formed through discharge plasma sintering. The chemical formula of the SnTe-based thermoelectric material is Sn 2.9‑X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The application significantly improves the thermoelectric figure of merit of the SnTe-based thermoelectric material and improves the thermoelectric performance of the SnTe-based thermoelectric material by doping tungsten elements in the SnTe matrix and compounding the two metal compounds of In2Te3 and Cu2Te.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric technology, and in particular to a SnTe-based thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric technology, which can directly convert heat energy into electrical energy or conversely create temperature differences through electricity, has gradually become a research hotspot due to its ability to effectively utilize various waste heat resources, such as industrial waste heat and solar energy. Compared with traditional power generation methods, thermoelectric technology not only reduces dependence on fossil fuels but also improves energy efficiency, contributing to emission reduction and environmental protection.

[0003] Thermoelectric materials, with their high efficiency, environmental friendliness, and flexibility, have demonstrated broad application potential. For example, in the aerospace field, thermoelectric devices can meet the demand for efficient energy conversion, improving the energy utilization efficiency of spacecraft; in medical devices, thermoelectric materials can be used in noiseless, precise body temperature monitoring equipment; and in microelectronics, thermoelectric materials can provide stable power support for microelectronic devices. As the performance of thermoelectric materials continues to improve, they will play an increasingly important role in energy conversion and environmental protection, becoming one of the key technologies for addressing global energy challenges. The conversion efficiency of thermoelectric materials is usually quantified by the thermoelectric figure of merit ZT, with the formula ZT = S 2 σT / (κ e +κ lat ), where S represents the Seebeck coefficient, σ is the conductivity, T is the absolute temperature, and κ is the electrical conductivity. e and κ lat These represent carrier thermal conductivity and lattice thermal conductivity, respectively. The key to improving the ZT value lies in increasing the Seebeck coefficient while simultaneously decreasing the material's lattice thermal conductivity. However, S, σ, and κ... e The mutual coupling between these three factors poses a challenge to achieving a high ZT value. Therefore, decoupling these three factors is the key to improving the ZT value.

[0004] SnTe-based thermoelectric materials are ideal for mid-temperature thermoelectric applications due to their non-toxicity and ease of synthesis. As an analogue of PbTe, environmentally friendly SnTe shows broad application prospects in large-scale commercial power generation. However, the high intrinsic Sn vacancies in SnTe lead to a high concentration of hole carriers, a low Seebeck coefficient, and a high carrier thermal conductivity, which limits its thermoelectric performance. Several strategies have been successfully applied to optimize the thermoelectric properties of SnTe, such as replacing Sn sites with cations (e.g., doping with Mn, Bi, Sr, and In) to improve the band structure (e.g., valence band convergence), thereby significantly increasing the Seebeck coefficient. However, this usually reduces electrical conductivity. Due to the strong coupling between the Seebeck coefficient and electrical conductivity, achieving a high thermoelectric figure of merit is not possible.

[0005] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0006] In view of the shortcomings of the prior art, the purpose of this invention is to provide a SnTe-based thermoelectric material and its preparation method, aiming to solve the problem that existing SnTe-based thermoelectric materials cannot achieve high thermoelectric figure of merit and have low thermoelectric performance.

[0007] The technical solution of the present invention is as follows:

[0008] In a first aspect, the present invention provides a method for preparing a SnTe-based thermoelectric material, wherein the SnTe-based thermoelectric material is composed of tungsten-doped SnTe, In2Te3, and Cu2Te, and the SnTe-based thermoelectric material is denoted as Sn. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 x = 0 to 0.15, and x does not take the value of 0;

[0009] The preparation method of the SnTe-based thermoelectric material includes the following steps:

[0010] S1. In an inert gas environment, according to the chemical formula Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The elements Te, Sn, In, Cu, and W are mixed in stoichiometric ratios to obtain a mixed raw material, which is then vacuum-sealed.

[0011] S2. The vacuum-sealed mixed raw materials are melted and reacted to obtain an ingot, and the ingot is annealed.

[0012] S3. After grinding the annealed ingot into powder, it is subjected to spark plasma sintering to obtain SnTe-based thermoelectric material.

[0013] Optionally, in step S1, the purity of the elemental Te, Sn, In, Cu, and W is greater than or equal to 99.999%.

[0014] The step of vacuum encapsulating the mixed raw materials specifically includes: transferring the mixed raw materials into a quartz tube and encapsulating the quartz tube using an oxyhydrogen flame in a vacuum environment.

[0015] Optionally, in step S2, the process conditions for the melting reaction include: heating the quartz tube from room temperature to 1200-1300K within 6-8 hours and holding it at that temperature for 8-12 hours; after the holding period, quenching the quartz tube in a supersaturated brine solution at room temperature.

[0016] Optionally, the process conditions for the melting reaction are as follows: the quartz tube is heated from room temperature to 1273K within 8 hours and held at that temperature for 10 hours; after the holding period, the quartz tube is quenched in a supersaturated brine solution at room temperature.

[0017] Optionally, in step S2, the annealing process conditions include: heating the ingot to 923-975K within 4-6 hours, holding it at that temperature for 1-3 days, and then cooling it to room temperature.

[0018] Optionally, the annealing process conditions are as follows: heating the ingot to 950K within 6 hours, holding it at that temperature for 3 days, and then cooling it to room temperature.

[0019] Optionally, in step S3, the process conditions for the discharge plasma sintering include: sintering in a vacuum environment at a temperature range of 600~700K and a pressure of 50~60MPa for a sintering time of 5~10 minutes.

[0020] Optionally, the process conditions for the spark plasma sintering are as follows: sintering is carried out in a vacuum environment at a temperature of 673 K and a pressure of 52 MPa for 10 minutes.

[0021] In a second aspect, the present invention provides a SnTe-based thermoelectric material, wherein the SnTe-based thermoelectric material is prepared using the preparation method of the SnTe-based thermoelectric material described in the present invention.

[0022] A third aspect of the present invention provides a SnTe-based thermoelectric material, wherein the SnTe-based thermoelectric material is composed of tungsten-doped SnTe, In2Te3, and Cu2Te, and the SnTe-based thermoelectric material is denoted as Sn. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 x = 0~0.15, and x does not take the value of 0.

[0023] Beneficial Effects: This invention introduces tungsten (W) interstitial defects into SnTe and simultaneously composites it with In2Te3 and Cu2Te. This novel doping-composite method effectively decouples the strong coupling between the Seebeck coefficient and electrical conductivity, thereby improving the power factor and effectively reducing the lattice thermal conductivity, achieving a high thermoelectric figure of merit. Specifically, the W interstitial defects caused by the alloying of W and SnTe effectively reduce the formation energy of intrinsic Sn vacancy defects; the introduced In2Te3 and Cu2Te composite phases provide additional conductive channels for charge carriers, enhancing their migration ability. Under the combined effect of these two factors, the electrical conductivity of SnTe-based thermoelectric materials is improved. Furthermore, the band convergence and band flattening effects, as well as the introduction of numerous nanoprecipitates leading to a large number of interface and structural defects, result in strong scattering of low-energy phonons at these interfaces, thereby reducing bipolar diffusion and further improving the Seebeck coefficient. Furthermore, the introduction of a composite phase in the form of nanoprecipitates creates numerous interfaces, which enhance phonon scattering. This interface scattering from the composite phase significantly reduces carrier thermal conductivity. Excess W significantly exacerbates lattice distortion, as the excess W atoms introduce numerous defects and impurities into the lattice, leading to a substantial increase in phonon scattering. The lattice defects and potential impurity phases (such as W-enriched phases) together enhance phonon-phonon scattering and phonon-defect scattering, significantly reducing lattice thermal conductivity. Ultimately, this significantly improves the thermoelectric figure of merit of the SnTe-based thermoelectric material, thereby enhancing its thermoelectric performance. The SnTe-based thermoelectric material of this invention has a simple preparation process and a short preparation cycle. Attached Figure Description

[0024] Figure 1 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 XRD patterns of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1;

[0025] Figure 2 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The conductivity versus temperature dependence of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1;

[0026] Figure 3 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X WX Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The Seebeck coefficient versus temperature curves of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1;

[0027] Figure 4 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Power factor versus temperature dependence curves of thermoelectric materials and SnTe thermoelectric materials of Comparative Example 1;

[0028] Figure 5 Sn in Example 5 2.78 W 0.12 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Transmission electron microscope images of thermoelectric materials;

[0029] Figure 6 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The graphs showing the relationship between the total thermal conductivity and temperature of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1;

[0030] Figure 7 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 ZT value versus temperature dependence curves for the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1;

[0031] Figure 8 Examples 1-6 show different W concentrations and Sn compounds composed of two metal compounds. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bar graph showing the relationship between the average ZT value of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1 and the W concentration. Detailed Implementation

[0032] This invention provides a SnTe-based thermoelectric material and its preparation method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0033] In one embodiment, a method for preparing a SnTe-based thermoelectric material is provided, wherein the SnTe-based thermoelectric material is composed of tungsten-doped SnTe, In2Te3, and Cu2Te, and the SnTe-based thermoelectric material is denoted as Sn. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 x = 0 to 0.15, and x does not take the value of 0;

[0034] The preparation method of the SnTe-based thermoelectric material includes the following steps:

[0035] S1. In an inert gas environment, according to the chemical formula Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The elements Te, Sn, In, Cu, and W are mixed in stoichiometric ratios to obtain a mixed raw material. The mixed raw material is then vacuum-sealed, wherein x = 0~0.15, and x is not 0.

[0036] S2. The vacuum-sealed mixed raw materials are melted and reacted to obtain an ingot, and the ingot is annealed.

[0037] S3. After grinding the annealed ingot into powder, it is subjected to spark plasma sintering to obtain SnTe-based thermoelectric material.

[0038] In this embodiment, high-purity elemental metals are used as raw materials and proportioned according to stoichiometric ratios. The elemental metals are mixed, vacuum-sealed, and then melted to obtain an ingot. The ingot is then subjected to high-temperature annealing. After high-temperature annealing, the ingot is ground into powder and then subjected to spark plasma sintering (SPS) to form a dense, bulk SnTe-based thermoelectric material. The chemical formula of this SnTe-based thermoelectric material is Sn... 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18This embodiment significantly improves the thermoelectric figure of merit and enhances the thermoelectric performance of SnTe-based thermoelectric materials by doping tungsten (W) into the SnTe matrix and combining it with two metal compounds, In2Te3 and Cu2Te.

[0039] Specifically, by introducing W into SnTe, W defects are introduced into the interstitial lattice, thereby improving electrical transport performance. The introduction of the In₂Te₃ and Cu₂Te composite phases provides additional conductive channels and reduces bipolar diffusion, thus improving electrical transport performance. Simultaneously, the interstitial defects and lattice distortion introduced by tungsten doping, along with the formation of numerous interfaces by the composite phases in the form of nanoprecipitates, enhance phonon scattering. This combined strategy significantly reduces the lattice thermal conductivity. Therefore, this method effectively improves the thermoelectric figure of merit of SnTe-based thermoelectric materials, thereby enhancing their thermoelectric performance.

[0040] In one embodiment, in step S1, the purity of the element Te, the purity of the element Sn, the purity of the element In, the purity of the element Cu, and the purity of the element W are all greater than or equal to 99.999%.

[0041] The step of vacuum encapsulating the mixed raw materials specifically includes: transferring the mixed raw materials into a quartz tube and encapsulating the quartz tube using an oxyhydrogen flame in a vacuum environment.

[0042] In one embodiment, in step S2, the process conditions for the melting reaction include: slowly heating the quartz tube from room temperature to 1200-1300K over 6-8 hours and holding it at that temperature for 8-12 hours to ensure that the raw materials are fully melted and reacted completely; after the holding period, quenching the quartz tube in a supersaturated brine solution at room temperature.

[0043] In one embodiment, the process conditions for the melting reaction are as follows: the quartz tube is slowly heated from room temperature to 1273K within 8 hours and held at that temperature for 10 hours; after the holding period, the quartz tube is quenched in a supersaturated brine solution at room temperature.

[0044] In one embodiment, in step S2, the annealing process conditions include: heating the ingot to 923-975K within 4-6 hours, holding it at that temperature for 1-3 days, and then slowly cooling it to room temperature.

[0045] In one embodiment, the annealing process conditions are as follows: heating the ingot to 950K within 6 hours, holding it at that temperature for 3 days, and then slowly cooling it to room temperature.

[0046] In one embodiment, in step S3, the process conditions for spark plasma sintering include: sintering in a vacuum environment at a temperature range of 600-700K and a pressure of 50-60MPa for 5-10 minutes. Sintering under these temperature and pressure conditions ensures the densification of the product, ultimately yielding a high-density, bulk SnTe-based thermoelectric material.

[0047] In one embodiment, the spark plasma sintering process conditions are as follows: sintering is carried out in a vacuum environment at a temperature of 673 K and a pressure of 52 MPa for 10 minutes. Sintering under these temperature and pressure conditions can further improve the density of the product.

[0048] In one embodiment, a SnTe-based thermoelectric material is provided, wherein the SnTe-based thermoelectric material is composed of tungsten-doped SnTe, In2Te3, and Cu2Te, and the SnTe-based thermoelectric material is denoted as Sn. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 x = 0~0.15 (e.g., 0.03, 0.06, 0.09, 0.12, 0.15, etc.), and x does not take the value 0;

[0049] And / or, the SnTe-based thermoelectric material is prepared using the SnTe-based thermoelectric material preparation method described in any of the above embodiments.

[0050] The present invention will be further described in detail below through specific embodiments.

[0051] Example 1

[0052] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of thermoelectric material (x=0) is as follows:

[0053] S1. In an inert gas environment, according to the chemical formula Sn 2.9 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0054] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0055] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0056] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.9 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0057] Example 2

[0058] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of the thermoelectric material (x=0.03) is as follows:

[0059] S1. In an inert gas environment, according to the chemical formula Sn 2.87 W 0.03 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0060] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0061] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0062] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.87 W 0.03 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0063] Example 3

[0064] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of the thermoelectric material (x=0.06) is as follows:

[0065] S1. In an inert gas environment, according to the chemical formula Sn 2.84 W 0.06 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0066] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0067] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0068] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.84 W 0.06 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0069] Example 4

[0070] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of the thermoelectric material (x=0.09) is as follows:

[0071] S1. In an inert gas environment, according to the chemical formula Sn 2.81 W 0.09 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0072] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0073] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0074] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.81 W 0.09 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0075] Example 5

[0076] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of the thermoelectric material (x=0.12) is as follows:

[0077] S1. In an inert gas environment, according to the chemical formula Sn 2.78 W 0.12 Te 2.9-(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0078] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0079] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0080] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.78 W 0.12 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0081] Example 6

[0082] Sn in this embodiment 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The preparation method of the thermoelectric material (x=0.15) is as follows:

[0083] S1. In an inert gas environment, according to the chemical formula Sn 2.75 W 0.15 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Metallic elements Sn, Cu, In, and Te were weighed according to stoichiometric ratios, with each element having a purity greater than or equal to 99.999%. The elements were then uniformly mixed and transferred to a quartz tube, where flame sealing was performed using an oxyhydrogen generator under a vacuum environment with an absolute vacuum degree less than or equal to 0.1 Pa.

[0084] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, the quartz tube is immediately placed in cold water to quench to room temperature to obtain an ingot.

[0085] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0086] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform spark plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain high-density Sn. 2.75 W 0.15 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Bulk thermoelectric materials.

[0087] Compare with Example 1

[0088] The preparation method of the SnTe thermoelectric material in this comparative example is as follows:

[0089] S1. In an inert gas environment, weigh the elemental metals Sn and Te according to the stoichiometric ratio of the chemical formula SnTe, with the purity of each elemental metal being greater than or equal to 99.999%. Then, after uniformly mixing the elemental metals, transfer them to a quartz tube and perform flame sealing of the tube using a hydrogen-oxygen generator in a vacuum environment with an absolute vacuum degree of less than or equal to 0.1 Pa.

[0090] S2. Under vacuum conditions, the quartz tube after flame sealing in step S1 is placed in a box furnace and heated from room temperature to 1273K within 8 hours, and held at that temperature for 10 hours. After the holding time is completed, it is immediately placed in cold water for quenching to room temperature to obtain an ingot.

[0091] Under vacuum conditions, the ingot is subjected to high-temperature annealing. The high-temperature annealing process includes raising the quartz tube from room temperature to 950K within 6 hours, holding it at that temperature for 3 days, and then lowering it to room temperature.

[0092] S3. Grind the ingot after high-temperature annealing in step S2 into powder, and then perform discharge plasma sintering in a vacuum environment at a temperature of 673K, a pressure of 52MPa, and a time of 10 minutes to obtain SnTe block thermoelectric material.

[0093] Different W concentrations and Sn concentrations of the two metal compounds in Examples 1-6 above were compared. 2.9-X W X Te 2.9 -(In2Te3) 0.03-(Cu2Te) 0.18 The thermoelectric material and the SnTe thermoelectric material of Comparative Example 1 were subjected to the following tests.

[0094] 1. Phase analysis

[0095] X-ray diffraction (XRD) was used to analyze Sn at different W concentrations and in the composite of two metal compounds in Examples 1-6. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Phase analysis was performed on the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1, and the results are as follows: Figure 1 As shown, the vertical axis represents the intensity of the diffraction peak, and the horizontal axis 2θ represents the angle of the diffraction peak.

[0096] Figure 1 The results in (a) show that the main phase of all samples is of the SnTe structure. Additionally, as shown in Figure (a)... Figure 1 In (b), the diffraction peaks of the Cu2Te phase can be clearly observed at around 25°; at the same time, as... Figure 1 In (c), diffraction peaks of the In2Te3 phase are also clearly observed between 41° and 42°. The presence of these composite phases indicates that Cu2Te and In2Te3 form independent crystalline phases in the SnTe matrix, rather than being dissolved into the SnTe lattice. No W-containing impurity phases were found in the diffraction patterns of the W-doped samples during XRD analysis, presumably because the W content in the samples is small and does not reach sufficient solid solubility. However, as the W content (i.e., the X value) increases, the overall diffraction peaks shift to lower angles, indicating that the overall lattice parameter increases. Within the solid solution region, the increasing trend in the lattice parameter may originate from smaller W atoms occupying interstitial positions in the SnTe lattice, rather than being caused by replacing Sn atoms or filling Sn vacancies in the lattice.

[0097] 2. Electrical performance analysis

[0098] Thermoelectric performance evaluation device (Beijing CRIEO CTA-3) was used to evaluate the Sn content of different W concentrations and the combined two metal compounds in Examples 1-6. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The electrical properties of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1 were tested at temperatures ranging from 50 to 550 °C, and the corresponding conductivity (σ) and Seebeck coefficient (S) were obtained. The test results are as follows: Figure 2 and Figure 3 As shown.

[0099] The results show that the increase in conductivity is mainly due to the increase in hole carrier concentration, which leads to an increase in the Seebeck coefficient. This can be attributed to the band structure flattening and valence band convergence caused by W and the composite phase In₂Te₃. Although the increase in hole carrier concentration is detrimental to the Seebeck coefficient, overall, the Seebeck coefficient remains relatively excellent.

[0100] Power factor (PF) reflects the electrical transport capability of thermoelectric materials, such as Figure 4 As shown, the vertical axis PF represents the power factor, and the horizontal axis T represents the temperature. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The power factors of the inducted SnTe thermoelectric materials are higher than those of the undoped SnTe. The incorporation of high-valence W into the samples generates additional charge carriers. This process lowers the intrinsic Sn vacancy formation energy, thereby increasing the charge carrier concentration. For the composite phase Cu2Te, Cu2Te is a conductive phase, and its introduction aims to significantly increase the material's conductivity by increasing the total number of charge carriers. W doping can modulate the band structure, effectively merging the light vacancy valence band and the heavy hole band, thus maintaining or even increasing the thermoelectric potential (Seebeck coefficient) of the charge carriers at high temperatures, despite the increased carrier concentration. For In2Te3, the introduction of In2Te3 can further optimize the band flattening effect and promote the merging of the vacancy valence band. This band optimization increases the effective mass of the charge carriers, thereby increasing the Seebeck coefficient. Under the coupling effect of these parameters, the final Sn... 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The power factor of the thermoelectric material was significantly improved within the test range, demonstrating Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Thermoelectric materials have good electrical transport properties.

[0101] 3. Microstructure analysis

[0102] Sn in Example 5 2.78 W 0.12 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The microstructure of thermoelectric materials was analyzed. Figure 5 (a) is Sn 2.78 W0.12 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Transmission electron microscope images of thermoelectric materials. Figure 5 As shown in (b), the lattice fringes with a spacing of d = 3.59 Å correspond to the (006) crystal plane of Cu2Te. Figure 5 As shown in (c), the lattice fringes with a spacing of d = 2.208 Å correspond to the (123) crystal plane of WTe2. Figure 5 As shown in (d), the lattice fringes with a spacing of d = 2.18 Å correspond to the (822) crystal plane of In2Te3. Figure 5 As shown in (e), the lattice fringes with a spacing of d = 3.168 Å correspond to the (200) crystal plane of SnTe. Figure 5 As shown in (e), the interplanar spacing of the SnTe(200) plane is 3.168 Å. In addition, for... Figure 5 Inverse Fast Fourier Transform is performed on the SnTe region selected in (f). Figure 5 (g) reveals the presence of numerous dislocations and lattice distortions in the SnTe matrix, which are caused by size and mass differences between the introduced foreign atoms and the matrix.

[0103] 4. Thermal conductivity test

[0104] A laser thermal conductivity meter (model LFA457, manufactured by Netzsch GmbH, Germany) was used to analyze the different W concentrations and Sn concentrations of the two composite metal compounds in Examples 1-6. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The thermal conductivity of the thermoelectric material and the SnTe thermoelectric material of Comparative Example 1 were tested at temperatures ranging from 50 to 550 °C. The thermal conductivity (κ) of different thermoelectric materials was compared. tot ) Changes with temperature, such as Figure 6 As shown. All Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Total thermal conductivity (κ) of thermoelectric materials tot The thermal conductivity decreases with increasing W concentration, and the overall thermal conductivity of all composite and doped-composite thermoelectric materials is lower than that of intrinsic SnTe thermoelectric materials. Multi-sized microstructural defects (nanoprecipitates and lattice distortions) within the SnTe matrix enhance phonon-phonon and phonon-defect scattering effects, significantly suppressing lattice thermal conductivity. Through tests of electrical and thermal conductivity, the thermal conductivity of Sn can be calculated.2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The dimensionless thermoelectric figure of merit ZT of thermoelectric materials, such as Figures 7-8 As shown, due to the significant increase in power factor and decrease in total thermal conductivity across the entire temperature range, all Sn... 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The average ZT value of thermoelectric materials within the test temperature range can be significantly improved, Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The thermoelectric material achieved an average ZT value of 0.313 in the range of 323–823 K, which is approximately 149.7% higher than that of the undoped-composite SnTe thermoelectric material. 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 Improving the average ZT value of thermoelectric materials within their operating temperature range is of practical significance for enhancing the conversion efficiency of thermoelectric devices.

[0105] Among them, Sn 2.78 W 0.12 Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The average power factor of the thermoelectric material is 16.96 μWcm in the range of 323–823 K. -1 K -2 The average ZT value reached 0.31, which is 96.8% and 149.7% higher than that of undoped-composite SnTe thermoelectric materials, respectively, thus significantly improving the thermoelectric performance of SnTe-based thermoelectric materials.

[0106] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for producing a SnTe-based thermoelectric material, characterized by, The SnTe-based thermoelectric material is compounded by SnTe doped with tungsten and In2Te3 and Cu2Te, the In2Te3 and Cu2Te form independent crystal phases in the SnTe matrix instead of being dissolved into the SnTe crystal lattice, and the SnTe-based thermoelectric material is denoted as Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 , x = 0.09-0.15; The preparation method of the SnTe-based thermoelectric material comprises the steps of: S1, in an inert gas environment, according to the chemical formula Sn 2.9-X W X Te 2.9 -(In2Te3) 0.03 -(Cu2Te) 0.18 The stoichiometric ratio of Te single element, Sn single element, In single element, Cu single element and W single element is mixed to obtain a mixed raw material, and the mixed raw material is vacuum packaged. S2, melting reaction of the vacuum-packaged mixed raw materials to obtain an ingot, and annealing treatment of the ingot; S3, grinding the ingot after the annealing treatment into a powder, and then performing spark plasma sintering to obtain the SnTe-based thermoelectric material; In step S1, the purity of the Te element, the purity of the Sn element, the purity of the In element, the purity of the Cu element and the purity of the W element are greater than or equal to 99.999%; The step of vacuum packaging the mixed raw materials specifically comprises: transferring the mixed raw materials into a quartz tube, and packaging the quartz tube by using a hydrogen-oxygen flame in a vacuum environment; In step S2, the process condition of the melting reaction is that the quartz tube is heated from room temperature to 1273K within 8 hours, and is kept for 10 hours; after the keeping, the quartz tube is placed in supersaturated brine at room temperature for quenching; In step S2, the process condition of the annealing treatment is that the ingot is heated to 950K within 6 hours, and is kept for 3 days before being cooled to room temperature; In step S3, the process condition of the spark plasma sintering is that the sintering is performed at a temperature of 673K and a pressure of 52MPa in a vacuum environment, and the sintering time is 10 minutes.

2. A SnTe-based thermoelectric material, characterized by, The SnTe-based thermoelectric material is prepared by the preparation method of the SnTe-based thermoelectric material according to claim 1.

Images