In-site isovalent doped cuin te2-based thermoelectric material and preparation method thereof

Abstract

The application belongs to the technical field of thermoelectric materials, and particularly relates to an In-site homovalent-doped CuInTe2-based thermoelectric material and a preparation method thereof. 1‑x Sb x Te2,0

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, specifically relating to an In-site isovalent doped CuInTe2-based thermoelectric material and its preparation method. Background Technology

[0002] Currently, clean and sustainable energy is playing an increasingly important role in the global carbon cycle. Solid-state thermoelectric technology, which can convert heat and electricity in an environmentally friendly manner to achieve waste heat collection and utilization, has attracted widespread attention. Furthermore, based on the Seebeck and Peltier effects, solid-state thermoelectric technology also has significant advantages in energy harvesting and solid-state refrigeration, respectively.

[0003] The effective conversion rate of solid-state thermoelectric modules is lower than that of Carnot engines and depends on the thermoelectric figure of merit ZT of the thermoelectric material, which can be expressed by the formula ZT = S 2 σT / κ is obtained, where S, σ, T, and κ represent the Seebeck coefficient, electrical conductivity, absolute temperature, and total thermal conductivity, respectively. CuInTe2 chalcopyrite has a tetragonal structure. CuInTe2 (#122), as a new type of electronic material, has attracted more attention in thermoelectric applications in recent years. However, due to the low Seebeck coefficient and conductivity of CuInTe2, it only has a moderate power factor PF (PF = S). 2 σ); at the same time, its inherent lattice thermal conductivity κ (κ≈6~9W·m) -1 ·K -1 The relatively high K (303K) of CuInTe2 results in a low thermoelectric figure of merit ZT, which limits its application in thermoelectric generators. Summary of the Invention

[0004] The purpose of this invention is to provide an In-site isovalent doped CuInTe2-based thermoelectric material and its preparation method. The In-site isovalent doped CuInTe2-based thermoelectric material provided by this invention has a low lattice thermal conductivity and a high thermoelectric figure of merit (ZT).

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides an In-site isovalent doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1:

[0007] CuIn 1-x Sb x Te2 formula 1;

[0008] In Equation 1, 0 <x<0.5。

[0009] Preferably, the foreign metal element Sb is doped with p-type doping.

[0010] This invention provides a method for preparing the In-site isovalent doped CuInTe2-based thermoelectric material as described above, comprising the following steps:

[0011] According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Sb and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot.

[0012] The ingot was sequentially subjected to mechanical crushing and wet ball milling to obtain precursor powder;

[0013] The precursor powder is subjected to stepwise hot pressing sintering to obtain the In-site isovalent doped CuInTe2-based thermoelectric material.

[0014] Preferably, the step-by-step hot pressing sintering includes the following steps: under pressure, the precursor powder is heated from room temperature to an intermediate temperature at a first temperature rise rate, and then held at an intermediate temperature; then the intermediate temperature is heated to the sintering temperature at a second temperature rise rate, and then held at a temperature and pressure for sintering.

[0015] Preferably, the intermediate temperature is 430–480°C, and the intermediate holding time is 15–50 min.

[0016] Preferably, the sintering temperature is 480–560°C; the pressure applied is 40–70 MPa; and the holding and pressure sintering time is 40–80 min.

[0017] Preferably, the first temperature rise rate is 8 to 15 °C / min.

[0018] Preferably, the second temperature rise rate is 3 to 6 °C / min.

[0019] Preferably, after the step-by-step hot pressing sintering, the hot-pressed sintering product is cooled under a pressure of 0-5 MPa to obtain the In-site isovalent doped CuInTe2-based thermoelectric material; the cooling rate is 20-40 °C / min.

[0020] Preferably, the vacuum degree of the vacuum melting is on the order of 10. -3 Pa, the temperature is ≥1100℃, the holding time is 12~24h; the quenching temperature is 800~1050℃; the annealing temperature is 401~500℃, the holding time is 24~48h.

[0021] This invention provides an In-site isovalent doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1: CuIn 1-x Sb xEquation 1 for Te2; in Equation 1, 0 < x < 0.5. This invention increases the effective mass of the density of states of CuInTe2 by isovalently doping Sb at the In site, thereby significantly improving the Seebeck coefficient of the In-site isovalently doped CuInTe2 thermoelectric material. On the other hand, due to the presence of the Sb dopant, the increased structural entropy in the material is effectively balanced with the carrier concentration and mobility, thereby effectively reducing the lattice thermal conductivity of the thermoelectric material, further reducing the intrinsic thermal conductivity. Considering all the above factors, the ZT of the In-site isovalently doped CuInTe2-based thermoelectric material provided by this invention is significantly improved, contributing to the improvement of thermoelectric material performance. Data from the embodiments show that, across the entire temperature range, the In-site isovalently doped CuInTe2-based thermoelectric material provided by this invention exhibits low lattice thermal conductivity and high thermoelectric figure of merit, significantly improving electrothermal performance. Data from the embodiments show that the thermoelectric figure of merit of the In-site isovalently doped CuInTe2-based thermoelectric material provided by this invention is 0.90 at 823 K, and the average thermoelectric figure of merit from 323 to 823 K is 0.35.

[0022] This invention also provides a method for preparing the In-site isovalent doped CuInTe2-based thermoelectric material described in the above-mentioned technical solution, comprising the following steps: Cu, In, Sb, and Te are mixed and vacuum-melted according to the stoichiometric ratio of each element in the chemical formula shown in Formula 1; the resulting melt is then quenched and annealed sequentially to obtain an ingot; the ingot is then mechanically crushed and wet-milled sequentially to obtain a precursor powder; the precursor powder is then subjected to stepwise hot-pressing sintering to obtain the In-site isovalent doped CuInTe2-based thermoelectric material. The preparation method provided by this invention is simple and suitable for mass production.

[0023] Furthermore, in this invention, the annealing temperature is 401–500°C, and the holding time is 24–48 hours. The preparation method provided by this invention shortens the annealing time to two-thirds of that in traditional processes, reducing the annealing process time, improving production efficiency, and to a certain extent achieving energy conservation and emission reduction, making it suitable for mass production. Attached Figure Description

[0024] Figure 1 The above is a flowchart of the synthesis process of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5.

[0025] Figure 2 The XRD patterns of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5 are shown.

[0026] Figure 3 The Seebeck coefficient of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5;

[0027] Figure 4 The lattice thermal conductivity of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5;

[0028] Figure 5 ZT values ​​of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5;

[0029] Figure 6 ZT is the thermoelectric material obtained in Comparative Example 1 and Examples 1-5. avg (303~823K), ZT avg (573~823K) values. Detailed Implementation

[0030] This invention provides an In-site isovalent doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1:

[0031] CuIn 1-x Sb x Te2 Formula 1;

[0032] In Equation 1, 0 < x < 0.5.

[0033] In this invention, unless otherwise specified, all raw materials / components used in the preparation are commercially available products well known to those skilled in the art.

[0034] In this invention, the foreign metal element Sb is preferably p-type doped.

[0035] In this invention, the In-site isovalent doped CuInTe2-based thermoelectric material is preferably a p-type material.

[0036] In this invention, x in Formula 1 is preferably 0 < x ≤ 0.3, specifically 0.03, 0.05, 0.1, 0.2 or 0.3.

[0037] In this invention, the In-site isovalent doped CuInTe2-based thermoelectric material is preferably CuIn 0.97 Sb 0.03 Te2, CuIn 0.95 Sb 0.05 Te2, CuIn 0.9 Sb 0.1 Te2, CuIn 0.8 Sb 0.2 Te2 or CuIn 0.7 Sb 0.3 Te2.

[0038] This invention provides a method for preparing the In-site isovalent doped CuInTe2-based thermoelectric material as described above, comprising the following steps:

[0039] According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Sb and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot.

[0040] The ingot was sequentially subjected to mechanical crushing and wet ball milling to obtain precursor powder;

[0041] The precursor powder is subjected to stepwise hot pressing sintering to obtain the In-site isovalent doped CuInTe2-based thermoelectric material.

[0042] According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Sb and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot.

[0043] In this invention, the vacuum degree of the vacuum melting is preferably on the order of 10. -3 Pa. The vacuum melting temperature is preferably ≥1100℃, specifically preferably 1100℃. The holding time for vacuum melting is preferably 12-24 hours. The vacuum melting is preferably carried out by sealing the above-mentioned elemental raw materials in a vacuum high-temperature resistant glass tube and then in a box furnace.

[0044] In this invention, the quenching temperature is preferably 800–1050°C, more preferably 950°C; the quenching medium is preferably water. The temperature of the quenching medium is preferably ≤20°C, more preferably 20°C. In this invention, the quenching process is preferably as follows: the melt obtained from vacuum melting is cooled to the quenching temperature, and then immersed in the quenching medium for quenching. The cooling rate is preferably 2°C / min.

[0045] In this invention, the annealing temperature is preferably 401–500℃, more preferably 450℃; the holding time is preferably 24–72 h, more preferably 48 h. In this invention, the annealing holding time is shortened to 2 / 3 of that in traditional processes. This shortened holding time improves production efficiency, achieves energy conservation and emission reduction to a certain extent, and is suitable for mass production.

[0046] After obtaining the ingot, the present invention sequentially performs mechanical crushing and wet ball milling on the ingot to obtain precursor powder.

[0047] In this invention, the mechanical crushing pressure is preferably 10 MPa.

[0048] In this invention, the medium used in the wet ball milling is preferably ethanol, the solid-liquid ratio is preferably 1:35, the ball-to-material ratio is preferably 20:1, and the rotation speed of the wet ball milling is preferably 650 r / min.

[0049] In this invention, the precursor powder is preferably a micro-nano powder, and the particle size of the precursor powder is preferably 0-53 μm, and not 0.

[0050] After obtaining the precursor powder, the present invention performs step hot pressing sintering on the precursor powder to obtain the In-site isovalent doped CuInTe2-based thermoelectric material.

[0051] In this invention, the step-by-step hot pressing sintering preferably includes the following steps: under pressure, the precursor powder is heated from room temperature to an intermediate temperature at a first temperature rise rate and held at an intermediate temperature; then the intermediate temperature is heated to the sintering temperature at a second temperature rise rate and held at a temperature and pressure for sintering.

[0052] In this invention, the pressure applied is preferably 35-55 MPa, more preferably 40-50 MPa.

[0053] In this invention, the intermediate temperature is preferably 430–480°C, more preferably 470°C. The intermediate holding time is preferably 10–60 min, more preferably 20–40 min. In this invention, the first temperature rise rate is preferably 8–15°C / min, more preferably 15°C / min.

[0054] In this invention, the sintering temperature is preferably 480–560°C, more preferably 490–520°C; the holding and pressure sintering time is preferably 30–120 min, more preferably 50–100 min. In this invention, the second temperature rise rate is preferably 3–8°C / min, more preferably 5°C / min.

[0055] In this invention, the walking beam hot pressing sintering is preferably performed by placing the precursor powder in a graphite mold within a hot pressing sintering furnace. In this invention, the graphite mold is preferably cylindrical. The inner diameter of the graphite mold is preferably 13 mm, and the inner wall of the graphite mold is preferably lined with a graphite paper tube, the thickness of which is preferably 0.1 mm. Before and after the precursor powder is placed in the graphite mold, this invention preferably places several graphite paper spacers on the bottom surface of the inner cavity of the graphite mold and on the surface of the powder before assembling the mold.

[0056] Following the step-by-step hot-pressing sintering, the present invention preferably further includes cooling the hot-pressed product under a pressure of 0–5 MPa to obtain the In-site doped CuInTe2-based thermoelectric material. The cooling pressure is preferably 0.1–5 MPa, more preferably 1–4 MPa, and most preferably 2 MPa; the cooling rate is preferably 10–25 °C / min, more preferably 25 °C / min; and the final cooling temperature is room temperature.

[0057] This invention increases the effective mass of the density of states of CuInTe2 by isovalently doping with Sb at the In site, thereby significantly improving the Seebeck coefficient of the In-site isovalently doped CuInTe2 thermoelectric material. Furthermore, the increased structural entropy effectively balances carrier concentration and mobility, thus effectively reducing the lattice thermal conductivity of the thermoelectric material, further lowering its intrinsic thermal conductivity. Considering all these factors, the ZT of the In-site isovalently doped CuInTe2-based thermoelectric material provided by this invention is significantly improved, contributing to the performance improvement of thermoelectric materials. In conclusion, the In-site isovalently doped CuInTe2-based thermoelectric material provided by this invention is a p-type thermoelectric material with great application potential.

[0058] To further illustrate the present invention, the technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0059] Example 1

[0060] Thermoelectric material CuIn 0.97 Sb 0.03 The method for preparing Te2 includes the following steps:

[0061] According to CuIn 0.97 Sb 0.03 Te2 was prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3 Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0062] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0063] Several graphite paper spacers are placed at the bottom of a graphite mold with a graphite paper tube (0.1 mm thick) inside (Ф13 mm). 5 g of CuIn... 0.97 Sb 0.03 Te2 powder was placed inside, followed by several graphite paper spacers, and then the mold was assembled. In a hot-pressing sintering furnace, under a pressure of 55 MPa, the temperature was increased to 470°C at a rate of 15°C / min and held for 20 min; then increased to 510°C at a rate of 5°C / min and held for 60 min. Finally, under a pressure of 2 MPa, the temperature was decreased to room temperature at a rate of 25°C / min to obtain the thermoelectric material CuIn. 0.97 Sb0.03 Te2.

[0064] Example 2

[0065] Thermoelectric material CuIn 0.95 Sb 0.05 The method for preparing Te2 includes the following steps:

[0066] According to CuIn 0.95 Sb 0.05 Te2 was prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3 Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0067] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0068] Several graphite paper spacers are placed at the bottom of a graphite mold with a graphite paper tube (0.1 mm thick) inside (Ф13 mm). 5 g of CuIn... 0.95 Sb 0.05 Te2 powder was placed inside, followed by several graphite paper spacers, and then the mold was assembled. In a hot-pressing sintering furnace, the temperature was increased to 470℃ at a rate of 15℃ / min under a pressure of 55MPa and held for 20min; then increased to 510℃ at a rate of 5℃ / min and held for 60min. Finally, the temperature was decreased to room temperature at a rate of 25℃ / min under a pressure of 2MPa to obtain the thermoelectric material CuIn. 0.95 Sb 0.05 Te2.

[0069] Example 3

[0070] Thermoelectric material CuIn 0.9 Sb 0.1 The method for preparing Te2 includes the following steps:

[0071] According to CuIn 0.9 Sb 0.1 Te2 was prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0072] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0073] Several graphite paper spacers are placed at the bottom of a graphite mold with a graphite paper tube (0.1 mm thick) inside (Ф13 mm). 5 g of CuIn... 0.9 Sb 0.1 Te2 powder was placed inside, followed by several graphite paper spacers, and then the mold was assembled. In a hot-pressing sintering furnace, under a pressure of 55 MPa, the temperature was increased to 470°C at a rate of 15°C / min and held for 20 min; then increased to 510°C at a rate of 5°C / min and held for 60 min. Finally, under a pressure of 2 MPa, the temperature was decreased to room temperature at a rate of 25°C / min to obtain the thermoelectric material CuIn. 0.9 Sb 0.1 Te2.

[0074] Example 4

[0075] Thermoelectric material CuIn 0.8 Sb 0.2 The method for preparing Te2 includes the following steps:

[0076] According to CuIn 0.8 Sb 0.2 Te2 was prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3 Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0077] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0078] Several graphite paper spacers are placed at the bottom of a graphite mold with a graphite paper tube (0.1 mm thick) inside (Ф13 mm). 5 g of CuIn... 0.8 Sb0.2 Te2 powder was placed inside, followed by several graphite paper spacers, and then the mold was assembled. In a hot-pressing sintering furnace, under a pressure of 55 MPa, the temperature was increased to 470°C at a rate of 15°C / min and held for 20 min; then increased to 510°C at a rate of 5°C / min and held for 60 min. Finally, under a pressure of 2 MPa, the temperature was decreased to room temperature at a rate of 25°C / min to obtain the thermoelectric material CuIn. 0.8 Sb 0.2 Te2.

[0079] Example 5

[0080] Thermoelectric material CuIn 0.7 Sb 0.3 The method for preparing Te2 includes the following steps:

[0081] According to CuIn 0.7 Sb 0.3 Te2 was prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3 Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0082] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0083] Several graphite paper spacers are placed at the bottom of a graphite mold with a graphite paper tube (0.1 mm thick) inside (Ф13 mm). 5 g of CuIn... 0.7 Sb 0.3 Te2 powder was placed inside, followed by several graphite paper spacers, and then the mold was assembled. In a hot-pressing sintering furnace, under a pressure of 55 MPa, the temperature was increased to 470°C at a rate of 15°C / min and held for 20 min; then increased to 510°C at a rate of 5°C / min and held for 60 min. Finally, under a pressure of 2 MPa, the temperature was decreased to room temperature at a rate of 25°C / min to obtain the thermoelectric material CuIn. 0.7 Sb 0.3 Te2.

[0084] Comparative Example 1

[0085] The preparation method of thermoelectric material CuInTe2 includes the following steps:

[0086] The raw materials for the preparation of the elemental substance were weighed according to the CuInTe2 stoichiometric ratio and sealed in a vacuum high-temperature resistant glass tube using a tube sealing machine (10). -3 Pa), then vacuum high-temperature melting in a box furnace (1100℃, held for 24h), then cooling (cooling rate of 2℃) to 950℃ water quenching (water temperature of 20℃), and then annealing (450℃, held for 48h) to obtain ingots.

[0087] The ingot is subjected to mechanical crushing (pressure of 10 MPa) and wet ball milling (the ball milling medium is ethanol, the solid-liquid ratio is 1:35, the ball-to-material ratio is 20:1, and the preferred rotation speed of the wet ball mill is 650 r / min) to obtain micro-nano-scale powder.

[0088] Several graphite paper pads were placed at the bottom of a graphite mold with a 0.1mm thick graphite paper tube inside (Ф13mm). 5g of CuInTe2 powder was placed inside, followed by more graphite paper pads, and then the mold was assembled. In a hot-pressing sintering furnace, under a pressure of 55MPa, the temperature was increased to 470℃ at a rate of 15℃ / min and held for 20min; then increased to 510℃ at a rate of 5℃ / min and held for 60min. Finally, under a pressure of 2MPa, the temperature was decreased to room temperature at a rate of 25℃ / min to obtain the thermoelectric material CuInTe2.

[0089] Figure 1 This is a schematic diagram illustrating the synthesis of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5. (See attached diagram.) Figure 1 As shown, in this invention, a vacuum glass tube containing raw materials is placed in a box furnace for high-temperature melting. It is held at 1373K for 24 hours, then gradually cooled (at a rate of 2°C) to 1223K, and then water quenched. Figure 1 (As shown by the midpoint line). The glass tube was then annealed at 723K for 48 hours. This is compared to the traditional process (673K for 72 hours). Figure 1 Compared to the previous method, the annealing time in this invention is shortened by 33%, reducing the production cycle, improving production efficiency, and achieving energy conservation and emission reduction in production.

[0090] Figure 2 The images show the XRD patterns and partial magnified views of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5. From... Figure 2 As can be seen from the image, after Sb doping, the XRD pattern matches that of CuInTe2 (PDF#97-060-0779), indicating that a uniform CuIn was synthesized. 1-x Sb xTe2 solid solution. As shown in the magnified partial image, with increasing Sb doping concentration, the diffraction peaks at 24.8° and 41.3° shift to higher angles. Simultaneously, with increasing doping concentration (x≥0.2), a small Sb2Te3 diffraction peak appears at 28.2°, indicating the presence of a second phase.

[0091] Figure 3 The Seebeck coefficient diagrams are shown for the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5. From... Figure 3 As can be seen from Example 3, CuIn 0.9 Sb 0.1 The Seebeck coefficient of Te2 at 323 K is 325 μV / K, which is 146% higher than that of the original CuInTe2 (132 μV / K) in Comparative Example 1. This is related to the improved effective mass of states (m * =9.01m0) related. Second only to CuIn prepared in step 3. 0.9 Sb 0.1 Te2, CuIn in Example 2 0.95 Sb 0.05 The Seebeck coefficient of Te2 at 323 K is 192 μV / K, which is 46% higher than that of the original CuInTe2 (132 μV / K) in Comparative Example 1. This is mainly related to the increased effective mass of the density of states and the effective trade-off between carrier concentration and mobility.

[0092] Figure 4 This is a lattice thermal conductivity diagram of the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5. Due to κ... e Relatively low, κ L It constitutes the majority of the total thermal conductivity. (By...) Figure 4 It can be seen that the κ of the sample L The decrease occurs as temperature increases. CuIn 0.95 Sb 0.05 Te2 achieved a low κ content of 0.53 W / m / K. L Second only to CuIn 0.7 Sb 0.3 The lattice thermal conductivity of Te2 is 0.34 W / m / K, which is lower than 0.35 W / m / K, representing the minimum limit of lattice thermal conductivity calculated by Cahill theory. The decrease in lattice thermal conductivity is explained based on the Debye-Callaway theoretical model. Strain fluctuations, compared to mass field fluctuations, play a dominant role in the decrease in lattice thermal conductivity. The dominant phonon scattering mechanism is the Umklapp scattering process between phonons. Therefore, point defects induced by Sb doping at In sites do indeed contribute to the decrease in CuIn. 1-x Sb x The decrease in lattice thermal conductivity of Te2 compounds.

[0093] Figure 5 The ZT and average ZT values ​​are shown for the thermoelectric materials obtained in Comparative Example 1 and Examples 1-5. From... Figure 5 As can be seen from the data, CuIn in Example 2 under room temperature conditions 0.95 Sb 0.05 The ZT of Te2 is 0.007, and the ZT value gradually increases with increasing temperature. At 823 K, CuIn 0.95 Sb 0.05 Te2 achieved the highest ZT value of 0.90, a 36% improvement compared to CuInTe2 (0.66). This is mainly due to the significant improvement in Seebeck's coefficient and the decrease in lattice thermal conductivity, which is related to the effective trade-off between carrier concentration and mobility. The average ZT values ​​of the thermoelectric materials were also calculated in the ranges of 303–823 K and 573–823 K.

[0094] Figure 6 ZT is the thermoelectric material obtained in Comparative Example 1 and Examples 1-5. avg (303~823K), ZT avg (573~823K) values. From Figure 6 As can be seen from ZT avg (303~823K), ZT avg The values ​​for (573–823 K) were 0.35 and 0.56, respectively, representing improvements of 66% and 65% compared to the original CuInTe2, confirming the effectiveness of Sb doping in improving CuIn... 0.95 Sb 0.05 The Te2 system has significant advantages in thermoelectric materials.

[0095] Meanwhile, the annealing time in the preparation methods provided in Examples 1-5 of this invention is 48 hours. That is, the CuIn provided by this invention... 1-x Sb x Te2 requires a relatively short annealing time to obtain products with excellent thermoelectric properties. This invention reduces the annealing holding time to 2 / 3 of the traditional process, thus achieving CuIn with excellent thermoelectric properties. 1-x Sb x Based on the Te2 product, the annealing holding time is shortened, production efficiency is improved, energy saving and emission reduction are achieved, and it is suitable for industrial mass production.

[0096] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing an In-site isovalent doped CuInTe2-based thermoelectric material, characterized in that, The In-site isovalent doped CuInTe2-based thermoelectric material has the chemical formula shown in Formula 1: CuIn 1-x Sb x Equation 1 (Te2); In Equation 1, x is 0.05; Includes the following steps: According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Sb and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot. The annealing temperature is 450℃ and the holding time is 48h. The ingot was sequentially subjected to mechanical crushing and wet ball milling to obtain precursor powder; The precursor powder is subjected to stepwise hot pressing sintering to obtain the In-site isovalent doped CuInTe2-based thermoelectric material. The stepwise hot pressing sintering includes the following steps: under pressure, the precursor powder is heated from room temperature to an intermediate temperature at a first temperature rise rate and held at the intermediate temperature; then, the intermediate temperature is heated to the sintering temperature at a second temperature rise rate and held at the temperature and pressure for sintering. The intermediate temperature is 430~480 ℃, the intermediate holding time is 15~50 min, and the sintering temperature is 480~560 ℃; the pressure is 40~70 MPa, and the holding time is 40~80 min.

2. The preparation method according to claim 1, characterized in that, In in-site isovalent doped CuInTe2-based thermoelectric materials, the doping of the foreign metal element Sb is p-type doping.

3. The preparation method according to claim 1, characterized in that, The first temperature rise rate is 8~15 ℃ / min.

4. The preparation method according to claim 1, characterized in that, The second temperature rise rate is 3~6 ℃ / min.

5. The preparation method according to claim 1, characterized in that, After the step-by-step hot pressing sintering, the product of the hot pressing sintering is cooled under a pressure of 0~5 MPa to obtain the In-site isovalent doped CuInTe2-based thermoelectric material; the cooling rate is 20~40℃ / min.

6. The preparation method according to claim 1, characterized in that, The vacuum degree of the vacuum melting is on the order of 10. -3 Pa, temperature is ≥1100 ℃, holding time is 12~24 h; the quenching temperature is 800~1050 ℃.

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