A type n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials, their preparation methods and applications

Abstract

This invention discloses a liquid thermoelectric material with low thermal conductivity n-type Ag4Sn0.5S2Te, its preparation method, and its application. The low thermal conductivity n-type Ag4Sn... 0.5 The chemical formula of S2Te-type liquid thermoelectric materials is Ag4Sn. 0.5 S2Te belongs to the cubic crystal system, space group; Ag4Sn 0.5 The chemical formula for creating Te vacancy defects in S2Te through thermoelectric performance optimization is Ag4Sn. 0.5 S2Te 0.92 The n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials consist of an anionic rigid framework composed of SnS4 tetrahedral units at the edge centers and Te atoms at the face centers, within which Ag ions move. This method employs a high-temperature vacuum solid-state synthesis technique to synthesize Ag4Sn materials. 0.5 S2Te exhibits 0.22–0.32 Wm at 300–823 K. ‑1 K ‑1 The material exhibits ultra-low thermal conductivity and is a uniformly molten compound that maintains a stable cubic phase in the range of 200–1100 K, modulated by Te vacancy defects and Ag4Sn. 0.5 S2Te 0.92 It achieves a thermoelectric figure of merit as high as 0.74, which is 95% higher than the intrinsic value.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to a type n Ag4Sn with low thermal conductivity. 0.5 S2Te-type liquid thermoelectric materials, their preparation methods, and applications. Background Technology

[0002] Thermoelectric devices enable the direct conversion between thermal energy and electrical energy. The energy conversion efficiency of the device is expressed by the dimensionless thermoelectric figure of merit ZT = S. 2 σT / κ tot The value is determined by S, where S is the Seebeck coefficient, σ is the conductivity, T is the absolute temperature, and κ is the finite element. tot (κ tot =κ ele +κ lat ) represents thermal conductivity, including electronic thermal conductivity (κ). ele ) and lattice thermal conductivity (κ) lat Clearly, simultaneously achieving a high power factor PF(S) is crucial. 2 σ) and low κ tot This is the key to obtaining a high ZT value.

[0003] Based on the concept of "phonon liquid-electron crystal (PLEC)," Ag-based argentite-germanium sulfide liquid materials possess intrinsically ultra-low κ. lat Compared with traditional liquid-like materials Cu 2-y Like X and Ag₂X (X = S, Se, and Te), it has become a new class of high-performance materials. These materials contain a large number of atoms in their unit cells, and Ag… + Its high fluidity and strong anharmonicity result in intrinsically ultra-low κ. lat Meanwhile, the rigid anionic framework with covalent bonds ensures carrier transport, similar to classical semiconductors. These two functional characteristics allow for independent control of electrical and thermal transport. However, as the temperature increases, traditional silver-germanium sulfide materials transform from a low-temperature ordered phase to a disordered cubic phase. Therefore, in order for devices to operate at high temperatures for extended periods, finding a novel thermoelectric material with a stable structure that does not undergo a phase transition within the test temperature range is a crucial problem that needs to be solved. 。 Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes an n-type Ag4Sn with low thermal conductivity. 0.5 S2Te-type liquid thermoelectric materials, their preparation methods, and applications.

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

[0006] A type n-type Ag4Sn with low thermal conductivity 0.5S2Te-type liquid thermoelectric materials, specifically the n-type Ag4Sn with low thermal conductivity. 0.5 The chemical formula of S2Te-type liquid thermoelectric materials is Ag4Sn. 0.5 S2Te belongs to the cubic crystal system. Space group; Ag4Sn 0.5 The chemical formula for creating Te vacancy defects in S2Te through thermoelectric performance optimization is Ag4Sn. 0.5 S2Te 0.92 The n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials consist of an anionic rigid framework composed of SnS4 tetrahedral units at the edge centers and Te units at the face centers, within which Ag ions move.

[0007] Preferably, the n-type Ag4Sn with low thermal conductivity 0.5 The cell parameters of S2Te-type liquid thermoelectric materials are: α=β=γ=90°, Z=6, unit cell volume

[0008] Preferably, the n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials exhibit ultra-low thermal conductivity (0.22-0.32 W / m²) in the range of 300-823 K. -1 K -1 It is a uniformly molten compound; the n-type Ag4Sn with low thermal conductivity 0.5 S2Te-type liquid thermoelectric materials maintain a stable cubic phase at 200-1100K.

[0009] A type n-type Ag4Sn with low thermal conductivity 0.5 The preparation method of S2Te-type liquid thermoelectric materials specifically includes the following steps:

[0010] S1. Prepare raw materials Ag granules, Sn granules, S granules and Te granules;

[0011] S2. Preparation of millimeter-scale single crystals: Weigh out 0.5g of elemental Ag, Sn, S, and Te according to the molar ratio, and place them in a quartz glass tube. Then, place the tube under a vacuum of 10... -5 -10 -1 The quartz tube was sealed with an oxyhydrogen flame under Pa conditions, and then sintered using a vacuum solid-state method.

[0012] Preparation of polycrystalline ingots: 6g of elemental Ag, Sn, S, and Te were weighed according to the molar ratio and placed into a quartz glass tube. The mixture was then heated under a vacuum of 10... -5 -10 -1 The quartz tube was sealed with an oxyhydrogen flame under Pa conditions and then sintered by vacuum melting.

[0013] S3. Grind the spontaneously crystallized single-crystal block sample obtained in step S2 to obtain millimeter-scale single crystals; grind the polycrystalline ingot sample obtained in step S2, and then sinter it using discharge plasma to obtain n-type Ag4Sn with low thermal conductivity. 0.5 S2Te type liquid thermoelectric materials.

[0014] Preferably, the purity of the elements Ag, Sn, S and Te in step S2 is greater than 99%.

[0015] Preferably, in step S2, the specific process of the millimeter-scale single crystal reaction is as follows: the temperature is uniformly increased from room temperature to 1000-1150℃ over 20-25 hours, held at that temperature for 3-7 days, and then cooled to room temperature at a rate of 2-7℃ / h to obtain millimeter-scale single crystals; the specific process of the polycrystalline ingot casting reaction is as follows: the temperature is increased to 1000℃ over 16 hours at a rate of 40-80℃ / h, held at that temperature for 2 days, and then quenched in ice water to obtain Ag4Sn. 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The compound was incubated at 550°C for 5 days.

[0016] Preferably, in step S3, the sintering temperature of the discharge plasma sintering is 500-600℃, the sintering time is 15-40min, and the sintering pressure is 40-60MPa.

[0017] Preferably, in step S3, the sintering time of the discharge plasma sintering is 37 min; the rate of heating to the sintering temperature is 50-100℃ / min.

[0018] A type n-type Ag4Sn with low thermal conductivity 0.5 Applications of S2Te-type liquid thermoelectric materials, specifically the low thermal conductivity n-type Ag4Sn... 0.5 S2Te-type liquid thermoelectric materials are used in the field of new energy as thermoelectric materials.

[0019] After adopting the above technical solution, the present invention has the following beneficial effects: the synthesis method of the present invention is simple and easy to operate, and can prepare millimeter-scale single crystal samples; the Ag4Sn synthesized by the present invention... 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 It has 0.22-0.32 W / m² at 300-823 K. -1 K -1 The material exhibits ultra-low thermal conductivity and is a uniformly molten compound that maintains a stable cubic phase in the range of 200-1100 K, modulated by Te vacancy defects and Ag4Sn. 0.5 S2Te 0.92It achieves a thermoelectric figure of merit as high as 0.74, which is 95% higher than the intrinsic value. Attached Figure Description

[0020] Figure 1 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te unit cell structure diagram;

[0021] Figure 2 The Ag4Sn prepared in Example 1 of this invention 0.5 Millimeter-scale single crystals of S2Te;

[0022] Figure 3 The Ag4Sn prepared in Example 1 of this invention 0.5 DSC curve of S2Te;

[0023] Figure 4 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Powder X-ray diffraction pattern;

[0024] Figure 5 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Conductivity as a function of temperature;

[0025] Figure 6 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Thermoelectric potential as a function of temperature;

[0026] Figure 7 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Thermal conductivity as a function of temperature;

[0027] Figure 8 The Ag4Sn prepared in Example 1 of this invention 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Thermoelectric figure of merit as a function of temperature. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] Prepare raw materials: Ag granules, Sn granules, S granules, and Te granules. The purity of the Ag granules is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of the Sn granules is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of the S granules is 99.999% (produced by Hebei Luohong Technology Co., Ltd.), and the purity of the Te granules is 99.99% (produced by Hebei Luohong Technology Co., Ltd.).

[0030] like Figures 1 to 8 As shown.

[0031] Example 1: Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Preparation

[0032] 1) Weigh out the elements Ag, Sn, S, and Te according to the molar ratio, and place them into a quartz glass tube. Then, place the tube under a vacuum of 10⁻⁶. -3 After evacuating under Pa conditions, the quartz tube is sealed with an oxyhydrogen flame.

[0033] 2) The sealed vacuum quartz tube from step 1) was placed in a muffle furnace for a solid-state reaction. The reaction conditions for millimeter-scale single crystals were: a uniform temperature increase from room temperature to 1000℃ over 20 hours, holding at 1000℃ for 3 days, followed by slow cooling to room temperature at a rate of 5℃ / h. The reaction conditions for polycrystalline powders were: a uniform temperature increase from room temperature to 1000℃ over 16 hours, holding at 1000℃ for 2 days, followed by ice-water quenching, and holding at 550℃ for 5 days.

[0034] 3) After spontaneous crystallization in step 2), millimeter-sized single crystals are obtained. The ingots obtained by ice-water quenching are thoroughly ground and then subjected to discharge plasma sintering. The sintering temperature of discharge plasma sintering is 550℃, the sintering time is 37min, and the sintering pressure is 45MPa, resulting in n-type Ag4Sn with low thermal conductivity. 0.5 S2Te type liquid thermoelectric materials.

[0035] Example 2: Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Preparation

[0036] 1) Weigh out the elements Ag, Sn, S, and Te according to the molar ratio, and place them in a quartz glass tube. Then, place the tube under a vacuum of 10⁻⁶. -2 After evacuating under Pa conditions, the quartz tube is sealed with an oxyhydrogen flame.

[0037] 2) The sealed vacuum quartz tube from step 1) was placed in a muffle furnace for a solid-state reaction. The reaction conditions for the millimeter-scale single crystal were: a uniform temperature increase from room temperature to 1050℃ over 22 hours, holding at 1000℃ for 3 days, and then slowly cooling to room temperature at a rate of 5℃ / h. The reaction conditions for the polycrystalline powder were: a uniform temperature increase from room temperature to 1000℃ over 16 hours, holding at 1000℃ for 2 days, followed by ice-water quenching to obtain Ag4Sn. 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The compound was incubated at 550°C for 5 days.

[0038] 3) After spontaneous crystallization in step 2), millimeter-sized single crystals are obtained. The ingots obtained by ice-water quenching are thoroughly ground and then subjected to discharge plasma sintering. The sintering temperature of discharge plasma sintering is 550℃, the sintering time is 37min, and the sintering pressure is 45MPa, resulting in n-type Ag4Sn with low thermal conductivity. 0.5 S2Te type liquid thermoelectric materials.

[0039] Example 3: Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 Preparation

[0040] 1) Weigh out the elements Ag, Sn, S, and Te according to the molar ratio, and place them in a quartz glass tube. Then, place the tube under a vacuum of 10⁻⁶. -1 After evacuating under Pa conditions, the quartz tube is sealed with an oxyhydrogen flame.

[0041] 2) The sealed vacuum quartz tube from step 1) was placed in a muffle furnace for a solid-state reaction. For the millimeter-scale single crystal, the reaction conditions were: a uniform temperature increase from room temperature to 1100℃ over 25 hours, holding at 1100℃ for 3 days, and then slowly cooling to room temperature at a rate of 5℃ / h. For the polycrystalline powder, the reaction conditions were: a uniform temperature increase from room temperature to 1000℃ over 16 hours, holding at 1000℃ for 2 days, followed by ice-water quenching to obtain Ag4Sn. 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The compound was incubated at 550°C for 5 days.

[0042] 3) After spontaneous crystallization in step 2), millimeter-sized single crystals are obtained. The ingots obtained by ice-water quenching are thoroughly ground and then subjected to discharge plasma sintering. The sintering temperature of discharge plasma sintering is 550℃, the sintering time is 37min, and the sintering pressure is 45MPa, resulting in n-type Ag4Sn with low thermal conductivity. 0.5 S2Te type liquid thermoelectric materials.

[0043] Performance testing:

[0044] 1) First, weigh out 0.5g of Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The compound (prepared in Example 1) was then ground into a powder using an agate mortar and pestle. Powder X-ray diffraction analysis was performed, and the results are as follows: Figure 4 As shown. The test angle was 10-70 degrees, and the X-ray diffraction peaks of the prepared samples were in perfect agreement with the calculated peaks. No impurity phases were observed.

[0045] 2) The Ag4Sn prepared in Example 1 was tested using a CTA thermoelectric material testing system from the domestic company Creo. 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The electrical properties of the compound were tested. The relationships between electrical conductivity and thermoelectric potential coefficient as a function of temperature were examined, such as... Figure 5 and Figure 6 As shown. The prepared Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The electrical conductivity of the compound increases with increasing temperature. The conductivity increases with increasing Te vacancies. At 823 K, Ag4Sn... 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The electrical conductivity is 8.29 S / cm. -1 and 31.82S cm -1 The prepared Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 The absolute value of the thermoelectric potential of the compound first increases and then decreases with increasing temperature. At 576 K and 691 K, Ag₄Sn… 0.5 The maximum peak thermoelectric potential of S2Te at 576 K is -446 μVK. -1 Ag4Sn 0.5 S2Te 0.92 The maximum peak thermoelectric potential at 691 K is -329 μV K. -1 .

[0046] 3) The thermal diffusivity D of the material prepared in Example 1 was tested using a Netzsch LFA467 laser flare thermal conductivity meter. The thermal conductivity was determined by κ = C. p Dρ is calculated, density ρ is obtained by Archimedes' displacement method, and specific heat C is... p The thermal conductivity was calculated using the Dulong-Petty formula. The relationship between thermal conductivity and temperature is as follows: Figure 7As shown. The thermal conductivity of the sample is not dependent on temperature. Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 It exhibits ultra-low thermal conductivity of 0.22-0.32 W / m² at 300-823 K. -1 K -1 .

[0047] 4) The Ag4Sn prepared in Example 1 0.5 The S2Te compound was ground into powder, and 5-10 mg was placed in a Φ4mm×2mm quartz glass crucible. A blank quartz glass crucible was also placed in the crucible as a reference. The material prepared in Example 1 was analyzed by DSC using an A HCT-2 (HENVEN) thermal analyzer at a heating rate of 10℃ / min. The curves are shown below. Figure 3 As shown. According to the DSC test results, Ag4Sn 0.5 The S2Te compound has a melting point of 1170 K and a crystallization point of 1142 K.

[0048] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A low thermal conductivity n-type Ag4Sn 0.5 S2Te-based liquid thermoelectric material, characterized by: The n-type Ag4Sn with low thermal conductivity 0.5 The chemical formula of S2Te liquid thermoelectric material is Ag4Sn 0.5 S2Te belongs to cubic system, Space group; Ag4Sn 0.5 The chemical formula of S2Te liquid thermoelectric material is Ag4Sn 0.5 S2Te 0.92 The n-type Ag4Sn with low thermal conductivity 0.5 The S2Te liquid thermoelectric material is composed of SnS4 tetrahedral base element at the edge center and Te at the face center position of the anion rigid framework, and Ag ions move in the anion rigid framework.

2. A low thermal conductivity n-type Ag4Sn 0.5 S2Te-based liquid thermoelectric material, characterized by, The n-type Ag4Sn having low thermal conductivity 0.5 The cell parameters of S2Te-based liquid thermoelectric material are: α = β = γ = 90°, Z = 6, unit cell volume 3. A low thermal conductivity n-type Ag4Sn 0.5 S2Te-based liquid thermoelectric material, characterized by: The low thermal conductivity n-type Ag4Sn 0.5 S2Te-based liquid thermoelectric materials have ultra-low thermal conductivity of 0.22-0.32 Wm -1 K -1 are congruent melting compounds; The low thermal conductivity n-type Ag4Sn 0.5 S2Te-based liquid thermoelectric materials maintain stable cubic phase from 200-1100 K.

4. A low thermal conductivity n-type Ag4Sn having the composition of any one of claims 1-3 0.5 A method for producing a S2Te-based liquid thermoelectric material, characterized by comprising the steps of: Specifically comprising the following steps: S1, preparing raw materials Ag particles, Sn particles, S particles and Te particles; S2, Preparation of millimeter single crystal: the total amount of 0.5 g of Ag, Sn, S and Te elements were weighed according to the molar ratio, and were loaded into a quartz glass tube. The quartz tube was sealed with hydrogen oxygen flame under the condition of 10 -5 -10 -1 Pa, and then was sintered by vacuum solid phase method. Preparation of polycrystalline ingot: 6 g of Ag, Sn, S and Te in total was weighed according to the molar ratio, and was put into a quartz glass tube. The quartz tube was sealed under the condition of 10 -5 -10 -1 Pa vacuum degree, and was sintered by vacuum melting method again. S3, grinding the monocrystalline bulk sample after spontaneous crystallization obtained in step S2 to obtain millimeter-level monocrystals; grinding the polycrystalline ingot sample obtained in step S2, and then sintering by using a discharge plasma to obtain n-type Ag4Sn with low thermal conductivity 0.5 S2Te-based liquid thermoelectric material.

5. A low thermal conductivity n-type Ag4Sn 0.5 The application relates to a preparation method of S2Te liquid thermoelectric material, characterized in that: The purity of the elemental Ag, Sn, S and Te in step S2 is greater than 99%.

6. A low thermal conductivity n-type Ag4Sn 0.5 A method for preparing S2Te-based liquid thermoelectric material, characterized in that, The specific process of the millimeter single crystal reaction in step S2 is: uniformly increasing the temperature from room temperature to 1000-1150℃ for 20-25 hours, keeping the temperature for 3-7 days, and then decreasing the temperature to room temperature at a rate of 2-7℃ / h to obtain a millimeter single crystal; the specific process of the polycrystal ingot reaction is: increasing the temperature to 1000℃ at a rate of 40-80℃ / h for 16 hours, keeping the temperature for 2 days, and then quenching in ice water to obtain Ag4Sn 0.5 S2Te and Ag4Sn 0.5 S2Te 0.92 compound, and keeping the temperature at 550℃ for 5 days.

7. A low thermal conductivity n-type Ag4Sn 0.5 The application relates to a preparation method of S2Te liquid thermoelectric material, characterized by comprising the following steps: In step S3, the sintering temperature of the discharge plasma sintering is 500-600℃, the sintering time is 15-40min, and the sintering pressure is 40-60Mpa.

8. A low thermal conductivity n-type Ag4Sn 0.5 The application relates to a preparation method of S2Te liquid thermoelectric material. In step S3, the sintering time of the discharge plasma sintering is 37min; the rate of temperature rise to the sintering temperature is 50-100℃ / min.

9. A low thermal conductivity n-type Ag4Sn as claimed in any one of claims 1-3 0.5 Use of a S2Te-based liquid thermoelectric material, characterized in that: The low-thermal-conductivity n-type Ag4Sn 0.5 The S2Te liquid thermoelectric material is applied to the new energy field as a thermoelectric material.

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