Multi-element solid solution p-type SnTe-based thermoelectric material and preparation method thereof

Abstract

The invention relates to a multi-element solid solution p-type SnTe-based thermoelectric material and a preparation method thereof, the chemical general formula of the SnTe-based thermoelectric material is Sn < 1-x-y > Te < 1-x > Cd < y > (CuSbS2) < x >, x is more than or equal to 0.05 and less than or equal to 0.2, and y is more than or equal to 0 and less than or equal to 0.09. According to the preparation method, smelting and spark plasma sintering are combined for preparation; the ternary compound CuSbS2 is introduced into SnTe, so that energy band convergence is realized, the energy valley number Nv is increased, chemical bonds are softened, phonon scattering is enhanced, and the lattice thermal conductivity is reduced. On this basis, the Cd element is further doped, so that the cation vacancy formation energy is reduced, the SnS second phase content is reduced, the carrier concentration is reduced, the state density effective quality is improved, the power factor is increased, the thermoelectric performance of the material is synergistically optimized in combination with multi-scale phonon scattering, and the maximum value reaches 0.7-1.0.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials technology, specifically to a multi-component solid solution p-type SnTe-based thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric materials are a class of functional materials capable of directly converting heat energy into electrical energy, and are widely used in low-grade heat recovery and solid-state refrigeration. High-performance thermoelectric materials should simultaneously possess a high power factor (S²σ) and a low total thermal conductivity (κ) to achieve a high dimensionless thermoelectric figure of merit (ZT). However, due to the significant coupling relationship between the Seebeck coefficient (S), electrical conductivity (σ), and total thermal conductivity (κ), the power factor is calculated by multiplying the electrical conductivity and the Seebeck coefficient. ZT is positively correlated with the power factor and negatively correlated with the total thermal conductivity. Achieving synergistic optimization of electrothermal transport performance remains a key challenge in thermoelectric material research. SnTe, as a typical group IV-VI narrow bandgap semiconductor thermoelectric material, is considered one of the ideal candidate materials to replace traditional PbTe due to its advantages such as non-toxicity, abundant resources, and good thermal stability.

[0003] However, SnTe is an intrinsic p-type semiconductor with a high concentration of Sn vacancies, resulting in a carrier concentration far exceeding the optimal value. Consequently, the Seebeck coefficient and power factor of the intrinsic material are low. Furthermore, SnTe exhibits high lattice thermal conductivity, with its intrinsic material typically having a maximum ZT value below 0.5 at 723 K. Therefore, current fabrication processes cannot achieve superior thermoelectric properties for SnTe materials. Summary of the Invention

[0004] The purpose of this invention is to solve the technical problem of poor thermoelectric performance of SnTe as a thermoelectric material. It provides a multi-component solid solution p-type SnTe-based thermoelectric material and its preparation method. By controlling the multi-component solid solution, the carrier concentration can be optimized to the optimal range, and multiple elements or components can be introduced to enhance phonon scattering, significantly reducing the lattice thermal conductivity, thereby improving the ZT value across the entire temperature range.

[0005] To achieve the above objectives, the present invention provides a multi-component solid solution p-type SnTe-based thermoelectric material, characterized in that: the general chemical formula of the SnTe-based thermoelectric material is Sn. 1-x-y Te 1-x Cd y (CuSbS2) xWhere 0.05≤x≤0.2, 0≤y≤0.09. This scheme, on the one hand, introduces the ternary compound CuSbS2 into SnTe to achieve band convergence. By introducing CuSbS2 and Cd as synergistic dopants, the band structure of SnTe is modulated, reducing the energy difference between the two valence bands and achieving band convergence, thereby improving the Seebeck coefficient and power factor. On the other hand, the introduced ternary compound CuSbS2 and Cd cause large fluctuations in the mass field and stress field, significantly enhancing phonon scattering and effectively suppressing lattice thermal conductivity. Ultimately, through synergistic optimization of electrical and thermal transport properties, the highest ZT value of the material can reach 0.7–1.0.

[0006] Preferably, x = 0.1 and y = 0.09.

[0007] A method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material includes the following steps:

[0008] S1. Weigh the raw materials: according to the chemical formula Sn 1-x-y Te 1-x Cd y (CuSbS2) x The chemical formula uses Sn, Te, Cd, Cu, Sb, and S as raw materials.

[0009] S2, Smelting: Under an oxygen-free environment, the raw materials weighed in S1 are placed into a container and heated. The band structure of SnTe is controlled by the synergistic doping of CuSbS2 and Cd elements. After cooling, the smelted alloy ingot is obtained.

[0010] S3, Crushing: Grind the alloy ingot obtained in S2 into powder;

[0011] S4. Sintering: The powder obtained in S3 is loaded into a high-temperature resistant container, and the loaded high-temperature resistant container is placed in a spark plasma sintering furnace for heating to obtain a sample of thermoelectric material.

[0012] This method employs a combination of melting and spark plasma sintering to prepare the material. By introducing the ternary compound CuSbS2 into SnTe, bandgap convergence is achieved, increasing the valley number Nv. Simultaneously, chemical bonds are softened, phonon scattering is enhanced, and lattice thermal conductivity is reduced. Furthermore, Cd is doped to lower the cation vacancy formation energy, reduce the SnS second-phase content, decrease the carrier concentration, and simultaneously increase the effective mass of the density of states and the power factor. Combined with multi-scale phonon scattering, the thermoelectric properties of the material are synergistically optimized, achieving a maximum value of 0.7 to 1.0.

[0013] Preferably, the raw materials Sn, Te, Cd, Cu, Sb and S in S1 have a purity of better than 99.9%.

[0014] To further improve the purity of the smelted alloy ingots, preferably, in step S2, the oxygen-free environment is a glove box filled with argon gas, with an oxygen concentration below 0.1 ppm and a water concentration below 0.1 ppm. The purpose of performing the smelting operation in a glove box filled with inert gas is to provide a highly inert, oxygen-free, and water-free environment for the smelting process, preventing the sample from reacting with air components. This avoids the formation of oxides from the reaction of raw materials with oxygen at high temperatures during smelting. The argon-filled environment maintains a low humidity level within the glove box, eliminating the impact of moisture on the raw materials and equipment, while ensuring operational safety.

[0015] Preferably, during the smelting process of S2, after the quartz tube is placed in the muffle furnace, the muffle furnace is heated to 1000°C at a heating rate of 1.4°C / min, and then held at 1000°C for 10 hours. After that, the temperature is lowered to 650°C at a cooling rate of 1.2°C / min, and then held at 650°C for 24 hours, and then allowed to cool naturally with the furnace.

[0016] Preferably, in step S3, the alloy ingot is ground into powder with a particle size of 1–10 μm using an agate mortar. By grinding the powder to a particle size range of 1–10 μm, it becomes suitable for subsequent densification treatment.

[0017] Preferably, during the sintering process of S4, the discharge plasma sintering temperature is 550℃~600℃, the pressure is 50~60 MPa, and the sintering time is 5~10 min, wherein the pressurization rate is 10~15 MPa / min and the heating rate is 50~100℃ / min.

[0018] The beneficial effects of this invention are as follows:

[0019] Through a multi-component solid solution approach, on the one hand, the band structure of SnTe is modulated by introducing the CuSbS2 ternary compound and Cd element as synergistic dopants, reducing the energy difference between the two valence bands and achieving band convergence, thereby improving the Seebeck coefficient and power factor. On the other hand, the introduced ternary compound and Cd element induce large fluctuations in the mass field and stress field, significantly enhancing phonon scattering and effectively suppressing lattice thermal conductivity. Ultimately, through synergistic optimization of electrical and thermal transport properties, the highest ZT value of the material can reach 0.7–1.0. Attached Figure Description

[0020] Figure 1 The p-type Sn prepared in Example 1 1-x-y Te 1-x Cd y (CuSbS2) x XRD patterns of thermoelectric materials.

[0021] Figure 2 The p-type Sn prepared in Example 11-x-y Te 1-x Cd y (CuSbS2) x Conductivity curves of the basic thermoelectric material.

[0022] Figure 3 The p-type Sn prepared in Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Seebeck coefficient curve of basic thermoelectric materials.

[0023] Figure 4 p-type Sn prepared in Comparative Example 1 and Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Comparison of band structure and density of states of basic thermoelectric materials.

[0024] Figure 5 The p-type Sn prepared in Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Power factor curve of the thermoelectric material.

[0025] Figure 6 (a) is the p-type Sn prepared in Example 1 1-x-y Te 1-x Cd y (CuSbS2) x The overall thermal conductivity curve of the basic thermoelectric material. Figure 6 (b) is the p-type Sn prepared in Example 1. 1-x-y Te 1-x Cd y (CuSbS2) x The lattice thermal conductivity curve of the basic thermoelectric material.

[0026] Figure 7 The p-type Sn prepared in Example 1 1-x-y Te 1-x Cd y (CuSbS2) x ZT value curve of the thermoelectric material.

[0027] Figure 8 The p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x XRD patterns of thermoelectric materials.

[0028] Figure 9 The p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Conductivity curves of the basic thermoelectric material.

[0029] Figure 10 The p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Seebeck coefficient curve of basic thermoelectric materials.

[0030] Figure 11 The p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Power factor curve of the thermoelectric material.

[0031] Figure 12 (a) is the p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Overall thermal conductivity curve of the basic thermoelectric material; Figure 12 (b) is the p-type Sn prepared in Example 2. 1-x-y Te 1-x Cd y (CuSbS2) x The lattice thermal conductivity curve of the basic thermoelectric material.

[0032] Figure 13 The p-type Sn prepared in Example 2 1-x-y Te 1-x Cd y (CuSbS2) x ZT value curve of the thermoelectric material.

[0033] Figure 14 p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x XRD patterns of thermoelectric materials.

[0034] Figure 15 p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Conductivity curves of the basic thermoelectric material.

[0035] Figure 16 p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Seebeck coefficient curve of basic thermoelectric materials.

[0036] Figure 17 p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Power factor curve of the thermoelectric material.

[0037] Figure 18 (a) p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x Overall thermal conductivity curve of the basic thermoelectric material; Figure 18 (b) p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x The lattice thermal conductivity curve of the basic thermoelectric material.

[0038] Figure 19 p-type Sn prepared in Comparative Example 1 1-x-y Te 1-x Cd y (CuSbS2) x ZT value curve of the thermoelectric material.

[0039] Figure 20 p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x XRD patterns of thermoelectric materials.

[0040] Figure 21 p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Conductivity curves of the basic thermoelectric material.

[0041] Figure 22 p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Seebeck coefficient curve of basic thermoelectric materials.

[0042] Figure 23 p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Power factor curve of the thermoelectric material.

[0043] Figure 24 (a) p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x Overall thermal conductivity curve of the basic thermoelectric material; Figure 24 (b) p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x The lattice thermal conductivity curve of the basic thermoelectric material.

[0044] Figure 25 p-type Sn prepared in Comparative Example 2 1-x-y Te 1-x Cd y (CuSbS2) x ZT value curve of the thermoelectric material.

[0045] Figure 26 p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x XRD patterns of thermoelectric materials.

[0046] Figure 27 p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x Conductivity curves of the basic thermoelectric material.

[0047] Figure 28 p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x Seebeck coefficient curve of basic thermoelectric materials.

[0048] Figure 29 p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) xPower factor curve of the thermoelectric material.

[0049] Figure 30 (a) p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x Overall thermal conductivity curve of the basic thermoelectric material; Figure 30 (b) p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x The lattice thermal conductivity curve of the basic thermoelectric material.

[0050] Figure 31 p-type Sn prepared in Comparative Example 3 1-x-y Te 1-x Cd y (CuSbS2) x ZT value curve of the thermoelectric material. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of the embodiments clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0052] In this disclosure, unless otherwise stated, directional terms such as "inner" and "outer" are defined based on the contours of the corresponding components. Terms such as "first" and "second" used in this disclosure are for distinguishing one element from another and do not imply sequence or importance.

[0053] This invention discloses a multi-component solid solution p-type SnTe-based thermoelectric material, wherein the general chemical formula of the SnTe-based thermoelectric material is Sn. 1-x-y Te 1-x Cd y (CuSbS2) x , where 0.05≤x≤0.2, 0≤y≤0.09.

[0054] Preferably, x = 0.1 and y = 0.09.

[0055] In this invention, the power factor (PF) is used.

[0056] Seebeck coefficient S, in units of VK -1 Conductivity σ, in units of S cm -1 PF=S 2 σ.

[0057] κ tot κ is the total thermal conductivity. lat is the lattice thermal conductivity.

[0058] Temperature T is Kelvin temperature, in units of K. In the performance verification of thermoelectric materials, this invention uses two temperature points: room temperature and 723K. The room temperature of this invention is 298K, and 723K is used as the characteristic temperature threshold for many materials. When tested in combination with room temperature, it can quickly locate the qualitative change point of material performance. The room temperature test reflects the basic functional indicators, while the 723K test can reflect the functional limit at high temperature.

[0059] A method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material includes the following steps:

[0060] S1. Weigh the raw materials: according to the chemical formula Sn 1-x-y Te 1-x Cd y (CuSbS2) x The chemical formula uses Sn, Te, Cd, Cu, Sb, and S as raw materials; the purity of the raw materials Sn, Te, Cd, Cu, Sb, and S is all better than 99.9%.

[0061] S2, Smelting: Under an oxygen-free environment, the raw materials weighed in S1 are placed into a container and heated. The band structure of SnTe is controlled by the synergistic doping of CuSbS2 and Cd elements. After cooling, the smelted alloy ingot is obtained.

[0062] S3. Grinding: Grind the alloy ingot obtained in S2 into powder; grind the alloy ingot into powder with a particle size of 1-10 μm using an agate mortar. By grinding the powder into a particle size range of 1-10 μm, it can be suitable for subsequent densification treatment.

[0063] S4. Sintering: The powder obtained in S3 is loaded into a high-temperature resistant container, and the loaded high-temperature resistant container is placed in a discharge plasma sintering furnace for heating to obtain a thermoelectric material sample. During the sintering process, the discharge plasma sintering temperature is 550℃~600℃, the pressure is 50~60 MPa, and the sintering time is 5~10 min, wherein the pressurization rate is 10~15 MPa / min and the heating rate is 50~100℃ / min.

[0064] The material was prepared by a combination of melting and spark plasma sintering. By introducing the ternary compound CuSbS2 into SnTe, band convergence was achieved, increasing the valley number Nv. At the same time, chemical bonds were softened, phonon scattering was enhanced, and the lattice thermal conductivity was reduced. On this basis, Cd element was further doped to reduce the cation vacancy formation energy, reduce the SnS second phase content, reduce the carrier concentration, increase the effective mass of the density of states, and increase the power factor. Combined with multi-scale phonon scattering, the thermoelectric properties of the material were synergistically optimized, with the highest value reaching 0.7 ~ 1.0.

[0065] The oxygen-free environment is a glove box filled with argon gas, with an oxygen concentration below 0.1 ppm and a water concentration below 0.1 ppm. The purpose of performing the melting operation in a glove box filled with inert gas is to provide a highly inert, oxygen-free, and water-free environment for the melting process, preventing the sample from reacting with air components. This avoids the formation of oxides from the reaction of raw materials with oxygen at high temperatures during melting. The argon-filled environment maintains a low humidity environment within the glove box, eliminating the impact of moisture on the raw materials and equipment, while ensuring operational safety. During the S2 melting process, after the quartz tube is placed in a muffle furnace, the furnace is heated to 1000℃ at a heating rate of 1.4℃ / min, held at 1000℃ for 10 hours, then cooled to 650℃ at a cooling rate of 1.2℃ / min, held at 650℃ for 24 hours, and then allowed to cool naturally with the furnace.

[0066] Example 1

[0067] A SnTe-based thermoelectric material is prepared by following these steps:

[0068] S1. Weigh the raw materials: according to the chemical formula Sn 1-x-y Te 1-x Cd y (CuSbS2) x The chemical formula uses Sn, Te, Cd, Cu, Sb, and S as raw materials.

[0069] In this case, x=0.1, y=0, and the purity of the raw materials Sn, Te, Cu, Sb, and S is all better than 99.9%.

[0070] S2. Melting: In an argon-filled glove box, the raw material weighed in S1 is placed into a graphite crucible. The graphite crucible is then placed into a vacuum-sealed quartz tube and sealed. The quartz tube is then placed in a muffle furnace and heated to 1000°C at a heating rate of 1.4°C / min. After holding at 1000°C for 10 hours, the temperature is lowered to 650°C at a cooling rate of 1.2°C / min. The temperature is then held at 650°C for 24 hours and allowed to cool naturally in the furnace to obtain the melted alloy ingot.

[0071] S3. Grinding: Grind the alloy ingot obtained in S2 into powder using an agate mortar and pestle. The resulting powder has a particle size of 1 to 10 μm.

[0072] S4. Sintering: Still in the glove box, the powder obtained in S3 is loaded into a graphite mold with a diameter of 12.7 mm. The graphite mold is placed in a spark plasma sintering furnace for heating. The temperature is increased at a rate of 50℃ / min, and the pressure is increased at a rate of 10 MPa / min. Finally, the temperature is held at 550℃ and 50 MPa axial pressure for 5 min to obtain a thermoelectric material sample with a density of 96% or higher.

[0073] The (SnTe) obtained in this embodiment 0.9 (CuSbS2) 0.1 The XRD diffraction pattern of the thermoelectric material is shown in the figure. Figure 1 In addition to the SnTe main phase, a distinct SnS second phase can be observed, indicating that the decomposition or reaction of some CuSbS2 produced this impurity phase.

[0074] (SnTe) 0.9 (CuSbS2) 0.1 The conductivity and Seebeck coefficient are shown in the figure. Figure 2 and Figure 3 The room temperature conductivity is 1799.4 S / cm, and the Seebeck coefficient is 40.8 μV / K; at 723 K, the conductivity is 769.0 S / cm, and the Seebeck coefficient is 144.7 μV / K. The positive Seebeck coefficient indicates that the material is p-type conductive. A comparison of the band structure and density of states of SnTe with that of SnTe after introducing CuSbS2 is shown in [reference needed]. Figure 4 , Figure 4 (a) shows the band structure of SnTe. Figure 4 (b) is (SnTe) 0.9 (CuSbS2) 0.1 The band structure of SnTe and, Figure 4 (c) represents SnTe and (SnTe) 0.9 (CuSbS2) 0.1 The density of states comparison diagram shows that the introduction of the CuSbS2 ternary compound can effectively improve the Seebeck coefficient by reducing the energy difference between the valence bands and causing band convergence, thereby improving the power factor.

[0075] (SnTe) 0.9 (CuSbS2) 0.1 The power factor changes with temperature as follows Figure 5 As shown, the power factors at room temperature and 723 K are 3.0 μW / mK² and 16.1 μW / mK², respectively, which are slightly lower than those of the sample in Comparative Example 1.

[0076] (SnTe)0.9 (CuSbS2) 0.1 Total thermal conductivity see Figure 6 (a) The total thermal conductivity is 2.9 W / mK at room temperature, and decreases to 1.8 W / mK at 723 K; (SnTe) 0.9 (CuSbS2) 0.1 The lattice thermal conductivity is shown in Figure 6 (b) The lattice thermal conductivity at room temperature is 1.7 W / mK, and it decreases to 0.8 W / mK at 723 K (SnTe). 0.9 (CuSbS2) 0.1 The total thermal conductivity and lattice thermal conductivity of the SnTe sample were significantly lower than those of the undoped CuSbS2 SnTe sample in Comparative Example 1. For example, the total thermal conductivity of Comparative Example 1 was 3.3 W / mK at 723 K. 0.9 (CuSbS2) 0.1 The ZT value changes with temperature as follows Figure 7 As shown, the maximum ZT value reaches 0.7 at 723 K; while the ZT value of the SnTe sample in Comparative Example 1 is only 0.4 at the same temperature. Compared with Comparative Example 1, this embodiment introduces CuSbS2, which generates additional scattering centers in the lattice, enhancing the phonon scattering effect and thus significantly reducing the lattice thermal conductivity. This improves the overall thermoelectric performance of the material without significantly sacrificing electrical transport properties.

[0077] Example 2

[0078] A SnTe-based thermoelectric material is prepared by following these steps:

[0079] S1. Weigh the raw materials: according to the chemical formula Sn 1-x-y Te 1-x Cd y (CuSbS2) x The chemical formula uses Sn, Te, Cd, Cu, Sb, and S as raw materials.

[0080] Where x=0.1, y=0.09, the purity of raw materials Sn, Te, Cd, Cu, Sb and S is better than 99.9%.

[0081] S2. Melting: In an argon-filled glove box, the raw material weighed in S1 is placed into a graphite crucible. The graphite crucible is then placed into a vacuum-sealed quartz tube and sealed. The quartz tube is then placed in a muffle furnace and heated to 1000°C at a heating rate of 1.4°C / min. After holding at 1000°C for 10 hours, the temperature is lowered to 650°C at a cooling rate of 1.2°C / min. The temperature is then held at 650°C for 24 hours and allowed to cool naturally in the furnace to obtain the melted alloy ingot.

[0082] S3. Grinding: Grind the alloy ingot obtained in S2 into powder using an agate mortar and pestle. The resulting powder has a particle size of 1 to 10 μm.

[0083] S4. Sintering: Still in the glove box, the powder obtained in S3 is loaded into a graphite mold with a diameter of 12.7 mm. The graphite mold is placed in a spark plasma sintering furnace for heating. The temperature is increased at a rate of 50℃ / min, and the pressure is increased at a rate of 10 MPa / min. Finally, the temperature is held at 550℃ and 50 MPa axial pressure for 5 min to obtain a thermoelectric material sample with a density of 96% or higher.

[0084] The Sn obtained in this embodiment 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 XRD patterns of thermoelectric materials as follows Figure 8 As shown, no obvious SnS second-phase peak is visible in the sample, indicating that Cd doping effectively suppressed the SnS second-phase precipitation that occurred in Comparative Example 2 after the introduction of CuSbS2. SnTe 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 The conductivity and Seebeck coefficient are respectively as follows: Figure 9 and Figure 10 As shown, the conductivity at room temperature is 1982.7 S / cm, and the Seebeck coefficient is 44.0 μV / K; at 773 K, the conductivity decreases to 638.3 S / cm, and the Seebeck coefficient increases to 173.2 μV / K. The positive Seebeck coefficient indicates that the material is a p-type thermoelectric conductor.

[0085] SnTe 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 The power factor changes with temperature as follows Figure 11 As shown, the values ​​are 3.8 μW / mK at room temperature and 773 K, respectively. 2 With 19.1 μW / mK 2 It exhibits excellent electrical transmission performance. Figure 12 (a) shows SnTe 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 The total thermal conductivity is 2.8 W / mK at room temperature, and decreases significantly to 1.5 W / mK at 773 K. (SnTe) 0.81 Te 0.9 Cd 0.09(CuSbS2) 0.1 The lattice thermal conductivity is shown in Figure 12 (b) The lattice thermal conductivity at room temperature is 1.5 W / mK, and the lattice thermal conductivity at 773 K decreases significantly to 0.7 W / mK. The significant decrease in lattice thermal conductivity is mainly attributed to the mass and stress field fluctuations after the introduction of CuSbS2 and the enhanced scattering of point defects caused by Cd doping.

[0086] like Figure 13 As shown, SnTe 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 The dimensionless thermoelectric figure of merit ZT at 773 K can reach up to 1.0.

[0087] This embodiment 2 uses (SnTe) that is undoped of Cd and has a SnS second phase, as described in embodiment 1. 0.9 (CuSbS2) 0.1 Compared to the sample in this embodiment, the introduction of Cd effectively suppressed the formation of the second phase, optimized the carrier concentration, slightly reduced the conductivity, and improved the Seebeck coefficient. In this embodiment 2, SnTe 0.81 Te 0.9 Cd 0.09 (CuSbS2) 0.1 The phonon group velocities are shown in Table 1. Cd doping reduces the phonon group velocity, thereby further reducing the lattice thermal conductivity and ultimately achieving a higher ZT value. Cd doping enhances phonon scattering by introducing point defects. Although the phonon group velocity in Example 2 is slightly higher than that in Example 1, it still significantly reduces the lattice thermal conductivity (1.46 W / mK < 1.69 W / mK). The ZT in this example is 1.0 at 773 K, while the ZT in Example 1 is only 0.7 at the same temperature. Specific performance indicators and comparisons are shown in Table 1. Figures 1-13 .

[0088] This embodiment employs a combination of melting and spark plasma sintering to prepare the material. By introducing the ternary compound CuSbS2 into SnTe, bandgap convergence is achieved, increasing the valley number Nv. Simultaneously, chemical bonds are softened, phonon scattering is enhanced, and lattice thermal conductivity is reduced. Furthermore, Cd is doped to lower the cation vacancy formation energy, reduce the SnS second-phase content, decrease the carrier concentration, and simultaneously increase the effective mass of the density of states and the power factor. Combined with multi-scale phonon scattering, the thermoelectric properties of the material are synergistically optimized.

[0089] The present invention also includes comparative examples and related experiments.

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that Sn in S11-x-y Te 1-x Cd y (CuSbS2) x The components shown are x=0, y=0, and the other experimental procedures are the same as in Example 1.

[0092] The XRD diffraction pattern of the SnTe-based thermoelectric material obtained in this comparative example is shown in [reference needed]. Figure 14 As can be seen, the sample contains only the SnTe main phase, with no other impurity phases detected, indicating good crystallization. The electrical conductivity and Seebeck coefficient of SnTe are shown in the figures below. Figure 15 and Figure 16 At room temperature, SnTe has a conductivity of 7960.4 S / cm and a Seebeck coefficient of 20.0 μV / K; at 773 K, the conductivity is 1109.4 S / cm and the Seebeck coefficient is 132.2 μV / K.

[0093] The power factor of SnTe is as follows Figure 17 As shown, the room temperature power factor is 3.2 μW / mK. 2 The power factor at 773 K is 19.4 μW / mK. 2 The total thermal conductivity of SnTe is as follows: Figure 18 As shown in (a), the total thermal conductivity is 9.0 W / mK at room temperature and 3.3 W / mK at 773 K; the lattice thermal conductivity of SnTe is as follows: Figure 18 As shown in (b), the lattice thermal conductivity is 3.2 W / mK at room temperature and 1.9 W / mK at 773 K, both higher than that of (SnTe) in Example 1. 0.9 (CuSbS2) 0.1 The lattice thermal conductivity of the samples at the same temperature indicates that the undoped CuSbS2 sample has a weaker phonon scattering ability.

[0094] The ZT value of Comparative Example 1 changes with temperature as follows: Figure 19 As shown, SnTe has a ZT value of 0.42 at 773 K, which is significantly lower than that of SnTe in Example 1. 0.9 (CuSbS2) 0.1 The ZT value was determined. The results show that without CuSbS2 doping, the material has a high lattice thermal conductivity and insufficient phonon scattering, which limits further improvement in thermoelectric performance.

[0095] Comparative Example 2

[0096] The difference between Comparative Example 2 and Example 1 is that Sn in S1 1-x-y Te 1-x Cd y (CuSbS2) xThe components shown are x=0.25, y=0, and the other experimental procedures are the same as in Example 1.

[0097] The (SnTe) obtained in this comparative example 0.75 (CuSbS2) 0.25 The XRD diffraction pattern of the thermoelectric material is shown in the figure. Figure 20 As can be seen, in addition to the main SnTe phase, there is a relatively obvious SnS second phase in the sample, and its diffraction peak intensity is significantly higher than that of the sample in Example 1, indicating that excessive CuSbS2 doping leads to significant second phase precipitation; that is, the CuSbS2 doping amount exceeds the preferred range of 0.05≤x≤0.2, which triggers significant SnS second phase precipitation.

[0098] (SnTe) 0.75 (CuSbS2) 0.25 The conductivity and Seebeck coefficient are shown in the figure. Figure 21 and Figure 22 The conductivity at room temperature is 293.3 S / cm and at 723 K is 162.3 S / cm, which is significantly lower than that of the intrinsic SnTe matrix (Comparative Example 1); the Seebeck coefficient at room temperature is 50.6 μV / K and at 723 K is 127.3 μV / K, which is slightly lower than that of Comparative Example 1.

[0099] (SnTe) 0.75 (CuSbS2) 0.25 The power factor is shown in Figure 23 The power factor at room temperature is 0.8 μW / mK. 2 The power factor at 723 K is 2.6 μW / mK. 2 The power factor decreased significantly compared to the intrinsic SnTe matrix (Comparative Example 1), mainly because the significant reduction in conductivity directly led to a significant decay in the power factor.

[0100] (SnTe) 0.75 (CuSbS2) 0.25 Total thermal conductivity as Figure 24 As shown in (a), the total thermal conductivity is 1.3 W / mK at room temperature and 0.9 W / mK at 723 K; (SnTe) 0.75 (CuSbS2) 0.25 The lattice thermal conductivity is as follows Figure 24 As shown in (b), the lattice thermal conductivity is 1.0 W / mK at room temperature and 0.7 W / mK at 723 K, which is significantly lower than that of the samples in Comparative Example 1 and Example 1, indicating that highly doped CuSbS2 can effectively enhance phonon scattering to reduce thermal conductivity.

[0101] Ultimately (SnTe) 0.75(CuSbS2) 0.25 The ZT value changes with temperature as follows Figure 25 As shown, the ZT value at room temperature is 0.02, and the ZT value at 723 K is 0.2, both significantly lower than that of Comparative Example 1. In this comparative example, the excessive CuSbS2 doping led to the formation of a distinct SnS second phase in the sample, causing a significant decrease in electrical conductivity, which in turn resulted in a substantial reduction in the power factor and ZT value. However, this also demonstrates that introducing the ternary compound CuSbS2 into SnTe can significantly reduce its thermal conductivity.

[0102] Comparative Example 3

[0103] The difference between Comparative Example 3 and Example 2 is that Sn in S1 1-x-y Te 1-x Cd y (CuSbS2) x The components shown are x = 0.1, y = 0.12, and the other experimental procedures are the same as in Example 2.

[0104] Sn obtained in this comparative example 0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 XRD diffraction patterns of thermoelectric materials as follows Figure 26 As shown, the main phase of the sample is SnTe structure, and no other obvious impurity phases are observed.

[0105] Sn 0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 The conductivity and Seebeck coefficient are shown in the figure. Figure 27 and Figure 28 The conductivity at room temperature was 1060.4 S / cm, and the conductivity at 773 K was 250.3 S / cm, which was significantly lower than that of the samples in Comparative Example 1 and Example 2. The Seebeck coefficient at room temperature was 59.1 μV / K, and the Seebeck coefficient at 773 K was 178.0 μV / K, which was slightly improved compared with the intrinsic SnTe matrix and the sample in Example 2.

[0106] Sn 0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 The power factor is shown in Figure 29 The power factor was 3.7 μW / mK² at room temperature and 7.9 μW / mK² at 773 K, which were significantly lower than those of Comparative Example 1 and Example 2. This was mainly because the significant decrease in conductivity offset the positive effect of the increase in Seebeck coefficient.

[0107] Sn0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 Total thermal conductivity as Figure 30 As shown in (a), the total thermal conductivity is 3.1 W / mK at room temperature and 1.6 W / mK at 773 K; Sn 0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 The lattice thermal conductivity is as follows Figure 30 As shown in (b), the lattice thermal conductivity at room temperature is 2.3 W / mK, and at 773 K it is 1.3 W / mK, which is significantly lower than that of the substrate, but not significantly different from the control effect in Example 2. Finally, Sn... 0.78 Te 0.9 Cd 0.12 (CuSbS2) 0.1 Its ZT value changes with temperature as follows: Figure 31 As shown, the ZT value is 0.04 at room temperature and 0.4 at 773 K. The ZT value is lower than that of Comparative Example 1 at high temperature, indicating that at this doping level, the reduction of the power factor becomes the main factor limiting the performance improvement.

[0108] The phonon group velocity, lattice thermal conductivity, and total thermal conductivity of different embodiments and comparative examples at room temperature are compared in Table 1 below.

[0109] Table 1:

[0110] As shown in Table 1, this comparative example 3 illustrates that in Sn 1-x-y Te 1-x Cd y (CuSbS2) x In the system, although excessive Cd doping slightly increases the Seebeck coefficient, it significantly reduces the power factor due to the substantial decrease in electrical conductivity, and the total thermal conductivity does not show significant improvement. In the end, the ZT value is lower than that of the intrinsic SnTe sample.

[0111] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A multi-component solid solution p-type SnTe-based thermoelectric material, characterized in that: The general chemical formula of the SnTe-based thermoelectric material is Sn 1-x-y Te 1-x Cd y (CuSbS2) x , where 0.05≤x≤0.2, 0≤y≤0.

09.

2. The multi-component solid solution p-type SnTe-based thermoelectric material according to claim 1, characterized in that: The values ​​are x = 0.1 and y = 0.

09.

3. A method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material, characterized in that: Includes the following steps: S1. Weigh the raw materials: according to the chemical formula Sn 1-x-y Te 1-x Cd y (CuSbS2) x The chemical formula uses Sn, Te, Cd, Cu, Sb, and S as raw materials. S2, Smelting: Under an oxygen-free environment, the raw materials weighed in S1 are placed into a container and heated. The band structure of SnTe is controlled by the synergistic doping of CuSbS2 and Cd elements. After cooling, the smelted alloy ingot is obtained. S3, Crushing: Grind the alloy ingot obtained in S2 into powder; S4. Sintering: The powder obtained in S3 is loaded into a high-temperature resistant container, and the loaded high-temperature resistant container is placed in a spark plasma sintering furnace for heating to obtain a sample of thermoelectric material.

4. The method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 3, characterized in that: The purity of the raw materials Sn, Te, Cd, Cu, Sb, and S in S1 is all better than 99.9%.

5. The method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 3, characterized in that: In S2, the anaerobic environment is a glove box filled with argon gas, with an oxygen concentration of less than 0.1 ppm and a water concentration of less than 0.1 ppm.

6. The method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 5, characterized in that: During the smelting process of S2, the smelting temperature is 900℃~1000℃, the holding time is 8~10 hours, and the temperature is lowered to 600℃~650℃ for annealing for 24 hours. The cooling method is natural cooling with the furnace.

7. The method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 3, characterized in that: During the S2 melting process, after the quartz tube is placed in the muffle furnace, the muffle furnace is heated at a heating rate of 1.4℃ / min. After reaching the melting temperature, it is held at that temperature. After holding at that temperature, it is cooled at a cooling rate of 1.2℃ / min to the annealing temperature and held at that temperature for 24 hours. Then, it is allowed to cool naturally with the furnace.

8. The method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 3, characterized in that: In step S3, the alloy ingot is ground into powder with a particle size of 1 to 10 μm using an agate mortar.

9. A method for preparing a multi-component solid solution p-type SnTe-based thermoelectric material according to claim 3, characterized in that: During the sintering process of S4, the discharge plasma sintering temperature is 550℃~600℃, the pressure is 50~60 MPa, and the sintering time is 5~10 min, wherein the pressurization rate is 10~15 MPa / min and the heating rate is 50~100 ℃ / min.

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