A B-site doped CuInTe2-based thermoelectric material and its preparation method

Abstract

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

Description

Technical Field

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

[0002] With the depletion of fossil fuels and their associated environmental pollution, clean and sustainable energy is playing an increasingly important role in the global carbon cycle. Solid-state thermoelectric technology, capable of reversibly and directly converting heat energy into electrical energy, has thus attracted widespread attention. Furthermore, solid-state thermoelectric technology, based on the Seebeck and Peltier effects, also possesses significant advantages in energy harvesting and solid-state refrigeration, respectively.

[0003] The performance of solid thermoelectric materials depends on the thermoelectric figure of merit ZT, 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 is a potentially valuable p-type thermoelectric material, but its Seebeck coefficient (S≈100~500μV·K) is limited. -1 (303K) and resistivity (σ≈1×10 4 Ω -1 ·m -1 This results in it having only 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 the application of CuInTe2 in the thermoelectric field. Summary of the Invention

[0004] The purpose of this invention is to provide a B-site doped CuInTe2-based thermoelectric material and its preparation method. The B-site 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 a B-site doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1:

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

[0008] In Equation 1, 0 < x < 0.1.

[0009] Preferably, the Ag doping is p-type doping.

[0010] This invention provides a method for preparing the B-site doped CuInTe2-based thermoelectric material 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, Ag 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 was hot-pressed and sintered to obtain the B-site doped CuInTe2-based thermoelectric material.

[0014] Preferably, the 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 400–420°C, and the intermediate holding time is 10–60 min.

[0016] Preferably, the sintering temperature is 450–550°C; the pressure applied is 35–55 MPa; and the holding and pressure sintering time is 30–120 min.

[0017] Preferably, the first temperature rise rate is 10-20℃ / min.

[0018] Preferably, the second temperature rise rate is 3 to 8 °C / min.

[0019] Preferably, after hot pressing and sintering, the hot-pressed and sintered product is cooled under a pressure of 0-5 MPa to obtain the B-site doped CuInTe2-based thermoelectric material; the cooling rate is 10-25 °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 1000~1100℃; the annealing temperature is 350~400℃, the holding time is 36~72h.

[0021] This invention provides a B-site doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1: CuIn 1- x Ag x Te2 formula 1;

[0022] In Equation 1, 0 < x < 0.1.

[0023] The thermoelectric material provided by this invention possesses high crystal symmetry, with a lattice distortion parameter ≈ 1. This invention increases the effective mass of CuInTe2's density of states by Ag doping at the B-site, while simultaneously reducing the carrier concentration, thereby significantly improving the Seebeck coefficient of the B-site-doped CuInTe2 thermoelectric material. On the other hand, the presence of the Ag dopant generates a severe Ag eccentricity effect in the material, effectively reducing the lattice thermal conductivity and further lowering the intrinsic thermal conductivity. Considering these factors, the ZT of the B-site-doped CuInTe2-based thermoelectric material provided by this invention is significantly improved, facilitating the application of thermoelectric devices. Data from the embodiments show that the thermoelectric material provided by this invention exhibits low lattice thermal conductivity and high thermoelectric figure of merit across the entire temperature range, significantly improving performance. Data from the embodiments show that the thermoelectric figure of merit of the B-site-doped CuInTe2-based thermoelectric material provided by this invention is 1.38 at 823 K, and the average thermoelectric figure of merit from 303 to 823 K is 0.67.

[0024] This invention also provides a method for preparing the B-site doped CuInTe2-based thermoelectric material described in the above technical solution, comprising the following steps: Cu, In, Ag, and Te are mixed and vacuum-melted according to the stoichiometric ratio of the elements 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-ball-milled sequentially to obtain a precursor powder; and the precursor powder is then hot-pressed and sintered to obtain the B-site micro-doped CuInTe2-based thermoelectric material. The preparation method provided by this invention is simple and suitable for mass production. Attached Figure Description

[0025] Figure 1 XRD patterns, lattice parameters, and lattice distortion parameters of the thermoelectric materials obtained in the comparative examples and embodiments;

[0026] Figure 2 The Seebeck coefficient of the thermoelectric materials obtained in the comparative examples and embodiments;

[0027] Figure 3 The lattice thermal conductivity of the thermoelectric materials obtained in the comparative examples and embodiments;

[0028] Figure 4 ZT, average ZT value and comparison of the thermoelectric materials obtained in the comparative examples and embodiments. Detailed Implementation

[0029] This invention provides a B-site doped CuInTe2-based thermoelectric material having the chemical formula shown in Formula 1:

[0030] CuIn 1-x Ag x Te2 formula 1;

[0031] In Equation 1, 0 < x < 0.1.

[0032] 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.

[0033] In this invention, Ag doping is p-type doping.

[0034] In this invention, the B-site doped CuInTe2-based thermoelectric material is a p-type material.

[0035] In this invention, x in Formula 1 is preferably 0 < x ≤ 0.05, specifically 0.01, 0.03 or 0.05.

[0036] In this invention, the B-site doped CuInTe2-based thermoelectric material is preferably CuIn 0.99 Ag 0.01 Te2, CuIn 0.97 Ag 0.03 Te2 or CuIn 0.95 Ag 0.05 Te2.

[0037] This invention provides a method for preparing the B-site doped CuInTe2-based thermoelectric material described above, comprising the following steps:

[0038] According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Ag and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot.

[0039] The ingot was sequentially subjected to mechanical crushing and wet ball milling to obtain precursor powder;

[0040] The precursor powder was hot-pressed and sintered to obtain the B-site doped CuInTe2-based thermoelectric material.

[0041] According to the stoichiometric ratio of each element in the chemical formula shown in Formula 1, Cu, In, Ag and Te are mixed and vacuum melted. The resulting melt is then quenched and annealed in sequence to obtain an ingot.

[0042] In this invention, the vacuum degree of the vacuum melting is preferably on the order of 10. -3Pa. 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.

[0043] In this invention, the quenching temperature is preferably 1000–1100℃, more preferably 1000℃; the quenching medium is preferably water. The temperature of the quenching medium is preferably ≤20℃, more preferably 20℃. In this invention, the quenching process is preferably as follows: the melt is heated to the quenching temperature and then immersed in the quenching medium for quenching.

[0044] In this invention, the annealing temperature is preferably 350-400°C, more preferably 400°C; the holding time is preferably 36-72h, more preferably 72h.

[0045] After obtaining the ingot, the present invention sequentially performs mechanical crushing and wet ball milling on the ingot to obtain precursor powder.

[0046] In this invention, the mechanical crushing pressure is preferably 10 MPa.

[0047] 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.

[0048] In this invention, the precursor powder is preferably separated at the micron level, and the particle size of the precursor powder is preferably 0 to 53 μm, and not 0.

[0049] After obtaining the precursor powder, the present invention performs hot pressing sintering on the precursor powder to obtain the B-site doped CuInTe2-based thermoelectric material.

[0050] In this invention, the 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.

[0051] In this invention, the intermediate temperature is preferably 400–420°C, more preferably 420°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 10–20°C / min, more preferably 12–18°C / min.

[0052] In this invention, the sintering temperature is preferably 450–550°C, more preferably 480–520°C; the pressure applied is preferably 35–55 MPa, more preferably 40–50 MPa; and 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 4–6°C.

[0053] In this invention, the hot pressing sintering is preferably performed by placing the precursor powder in a graphite mold within a hot pressing sintering furnace. 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 placing the precursor powder 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.

[0054] After hot pressing and sintering, the present invention preferably further includes cooling the hot-pressed sintered product under a pressure of 0-5 MPa to obtain the B-site doped CuInTe2-based thermoelectric material. The cooling pressure is preferably 0.1-1 MPa; the cooling rate is preferably 10-25 °C / min, more preferably 15-22 °C / min; and the final cooling temperature is room temperature.

[0055] The thermoelectric material prepared by this invention possesses high crystal symmetry, with a lattice distortion parameter approximately equal to 1. Due to the increased effective mass of the density of states and the decreased carrier concentration, the Seebeck coefficient of the thermoelectric material is significantly improved. Simultaneously, the presence of the dopant element induces a severe Ag eccentricity effect in the material, effectively reducing the lattice thermal conductivity and further decreasing the intrinsic thermal conductivity. Considering all these factors, the ZT of the thermoelectric material prepared by this invention is significantly improved. In conclusion, the B-site doped CuInTe2-based thermoelectric material provided by this invention is a p-type thermoelectric material with enormous application potential.

[0056] 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.

[0057] Example 1

[0058] Thermoelectric material CuIn 0.99 Ag 0.01 The method for preparing Te2 includes the following steps:

[0059] According to CuIn 0.99 Ag 0.01Te2 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), followed by water quenching at 1000℃ (water temperature is 20℃), and then annealing (400℃, held for 72h) to obtain the ingot.

[0060] 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.

[0061] 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... 0.99 Ag 0.01 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 420℃ at a rate of 15℃ / min and held for 20 min; then increased to 500℃ at a rate of 5℃ / min and subjected to a pressure of 45 MPa, held for 60 min. Finally, under a pressure of 0.5 MPa, the temperature was decreased to room temperature at a rate of 20℃ / min to obtain the thermoelectric material CuIn. 0.99 Ag 0.01 Te2.

[0062] Example 2

[0063] Thermoelectric material CuIn 0.97 Ag 0.03 The method for preparing Te2 includes the following steps:

[0064] According to CuIn 0.97 Ag 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), followed by water quenching at 1000℃ (water temperature is 20℃), and then annealing (400℃, held for 72h) to obtain the ingot.

[0065] 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.

[0066] 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 Ag 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, the temperature was increased to 420℃ at a rate of 15℃ / min and held for 20 min; then increased to 500℃ at a rate of 5℃ / min and subjected to a pressure of 45 MPa, held for 60 min. Finally, under a pressure of 0.5 MPa, the temperature was decreased to room temperature at a rate of 20℃ / min to obtain the thermoelectric material CuIn. 0.97 Ag 0.03 Te2.

[0067] Example 3

[0068] Thermoelectric material CuIn 0.95 Ag 0.05 The method for preparing Te2 includes the following steps:

[0069] According to CuIn 0.95 Ag 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), followed by water quenching at 1000℃ (water temperature is 20℃), and then annealing (400℃, held for 72h) to obtain the ingot.

[0070] 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.

[0071] 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 Ag 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 420℃ at a rate of 15℃ / min and held for 20 min; then increased to 500℃ at a rate of 5℃ / min and subjected to a pressure of 45 MPa, held for 60 min. Finally, under a pressure of 0.5 MPa, the temperature was decreased to room temperature at a rate of 20℃ / min to obtain the thermoelectric material CuIn. 0.95 Ag 0.05 Te2.

[0072] Comparative Example 1

[0073] The preparation method of thermoelectric material CuInTe2 includes the following steps:

[0074] The raw materials for the preparation of the element 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), followed by water quenching at 1000℃ (water temperature is 20℃), and then annealing (400℃, held for 72h) to obtain the ingot.

[0075] 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.

[0076] 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, the temperature was increased to 420℃ at a rate of 15℃ / min and held for 20min; then increased to 500℃ at a rate of 5℃ / min and subjected to a pressure of 45MPa, held for 60min. Finally, under a pressure of 0.5MPa, the temperature was decreased to room temperature at a rate of 20℃ / min to obtain the thermoelectric material CuInTe2.

[0077] Figure 1 The XRD patterns, lattice parameters, and lattice distortion parameters of the thermoelectric materials obtained in the comparative examples and embodiments are shown. Figure 1 As can be seen in (a), after Ag doping, a uniform CuIn was obtained. 1-x Ag x Te2 solid solution. After Rietveld refinement, the lattice parameters were obtained as follows: Figure 1 As shown in (b) above, the value of c gradually increases with the doping concentration. Figure 1 The lattice distortion parameter shown in (c) gradually decreases and gets closer to 1.

[0078] Figure 2 The Seebeck coefficient diagram is shown for the thermoelectric materials obtained in the comparative examples and embodiments. From... Figure 2 As can be seen from Example 3, CuIn 0.95 Ag 0.05 The Seebeck coefficient of Te2 at 303 K is 614 μV / K, which is 25% higher than that of the original CuInTe2 (492 μV / K) in the comparative example. This is related to their reduced carrier concentration and increased effective mass of the density of states (m* = 1.1m0).

[0079] Figure 3 This is a lattice thermal conductivity diagram of the thermoelectric materials obtained in the comparative examples and embodiments. From... Figure 3 As can be seen from this, at 303K, CuIn in Example 3 0.95 Ag 0.05 The lattice thermal conductivity of Te2 increased from 3.75 W / m² in the comparative example of the original CuInTe2. -1 K -1 It dropped to 2.75Wm -1 K -1 The lattice thermal conductivity decreased by 36.4%. The lattice thermal conductivity gradually decreased with temperature, reaching a relatively low lattice thermal conductivity of 0.7 W / m² at 823 K. -1 K -1 This is mainly related to the severe Ag eccentricity effect and the increased configurational entropy.

[0080] Figure 4 ZT values, average ZT values, and comparisons of the thermoelectric materials obtained in the comparative examples and embodiments are presented. Figure 4 As can be seen in (a) of Example 3, CuIn under room temperature conditions 0.95 Ag 0.05 The ZT of Te2 is 0.080, a significant increase of 370% compared to the ZT of the original CuInTe2 in the comparative example (0.017). As the temperature increases, CuIn... 0.95 Ag 0.05 Te2 achieved the highest ZT value of 1.38, an 18% improvement compared to CuInTe2. This is mainly due to the significant improvement in Seebeck's coefficient and the decrease in lattice thermal conductivity. Figure 4 As can be seen in (c), CuIn 0.95 Ag 0.05 Te2 has an excellent ZT value, second only to Cu. 0.8 Ag 0.20 InTe2, with a ZT of 1.58, is a thermoelectric material with great application potential. The average ZT values ​​of the thermoelectric material were also calculated between 303–823 K and 573–823 K. Figure 4 As can be seen in (b) of the text, ZT avg (303~823K), ZT avg The values ​​for (573–823 K) were 0.67 and 1.1, respectively, representing improvements of 34% and 26% compared to the original CuInTe2 in the comparative example. These average values ​​demonstrate a significant advantage in the same system. Figure 4 (d) in the middle.

[0081] 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 thermoelectric material CuIn 0.95 Ag 0.05 The method for preparing Te2 is characterized by, Includes the following steps: According to CuIn 0.95 Ag 0.05 Te2 is prepared by weighing the raw materials in stoichiometric proportions and sealing them in a vacuum high-temperature resistant glass tube using a sealing machine at a pressure of 10. -3 Pa, then vacuum high-temperature melting in a box furnace at 1100 ℃ for 24 h, followed by water quenching at 1000 ℃ with water at 20 ℃, and then annealing at 400 ℃ for 72 h to obtain the ingot. The ingots were sequentially subjected to mechanical crushing at a pressure of 10 MPa and wet ball milling with ethanol as the milling medium, a solid-liquid ratio of 1:35, a ball-to-material ratio of 20:1, and a wet ball milling speed of 650 r / min to obtain micro-nano-scale powders. A graphite paper pad is placed at the bottom of a graphite mold with an inner cavity of Ф13 mm and a graphite paper tube of 0.1 mm thickness; 5 g of CuIn is added. 0.95 Ag 0.05 Te2 powder was placed inside, followed by a graphite paper gasket, and then the mold was assembled. In a hot-pressing sintering furnace, the temperature was increased to 420 °C at a rate of 15 °C / min and held for 20 min; then increased to 500 °C at a rate of 5 °C / min and subjected to a pressure of 45 MPa, held for 60 min; finally, under a pressure of 0.5 MPa, the temperature was decreased to room temperature at a rate of 20 °C / min to obtain the thermoelectric material CuIn. 0.95 Ag 0.05 Te2.

Images