Silver bismuth sulphide structure thermoelectric material and method for producing the same

Abstract

The application discloses a silver bismuth sulfide ore structure thermoelectric material and a preparation method thereof. The silver bismuth sulfide ore structure thermoelectric material has a chemical formula of Pb5Sb 12+x Bi 6‑x Se 32 or Pb4Sb 12‑x Bi 8+x Se 34 ; in the Pb5Sb 12+x Bi 6‑x Se 32 , 0<=x<=5, the number of diagonal octahedrons in a layer formed by NaCl structure units of Pb5Sb 12+x Bi 6‑ x Se 32 is 8; in the Pb4Sb 12‑x Bi 8+x Se 34 , 0<=x<=6, the number of diagonal octahedrons in a layer formed by NaCl structure units of Pb4Sb 12‑x Bi 8+x Se 34 is 8; the Pb4Sb9Bi 11 Se 34 material obtained by the application has an intrinsic thermoelectric merit value of 0.48, the synthesis method is simple, the cost is low, the method can be popularized and applied on a large scale, and has a wide prospect.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, specifically relating to a silver bismuth sulfide structure thermoelectric material and its preparation method. Background Technology

[0002] The silver bismuth sulfide compound has a quasi-two-dimensional structure, consisting of a GeS structural unit forming layer connected to a NaCl structural unit forming layer. To distinguish the silver bismuth sulfide compound structurally, the number of octahedrons on the diagonal of the NaCl structural unit forming layer is used as the distinguishing factor. N To distinguish them, N The range is 2-8. Silver bismuth sulfide compounds possess advantages such as environmental friendliness and high abundance, and are widely used in optical materials, infrared detection materials, thermoelectric materials, and solar energy. However, with the rapid development of silver bismuth sulfide compounds in various fields, many silver bismuth sulfide compounds cannot meet the demands for higher performance, especially in the field of thermoelectric materials (e.g., highly tunable band gaps, combining high electrical conductivity and low thermal conductivity). Thermoelectric materials are environmentally friendly functional materials that can directly convert thermal energy into electrical energy, playing an irreplaceable role in technologies such as deep space exploration, waste heat recovery, and precise temperature control. However, the number of silver bismuth sulfide compounds known for thermoelectric applications is currently limited. Furthermore, while existing silver bismuth sulfide compounds have low lattice thermal conductivity, their electrical conductivity is also relatively low, and the intrinsic properties of the materials... ZT The values ​​are usually not high. Therefore, the search for multi-component, compositionally stable silver bismuth sulfide-structured thermoelectric materials is of great research significance. Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a silver-bismuth sulfide-structured thermoelectric material and its preparation method. By substituting elements into the silver-bismuth sulfide-structured compound, a quaternary Pb₅Sb₂ is obtained. 12+x Bi 6-x Se 32 and Pb4Sb 12-x Bi 8+x Se 34 Silver-bismuth sulfide structure thermoelectric materials, wherein the Pb4Sb9Bi obtained in this invention 11 Se 34 The material has an intrinsic thermoelectric figure of merit of 0.48 and can be used as a thermoelectric material.

[0004] The present invention adopts the following technical solution:

[0005] A silver-bismuth sulfide structured thermoelectric material, wherein the chemical formula of the silver-bismuth sulfide structured thermoelectric material is Pb5Sb 12+ x Bi 6-x Se 32or Pb4Sb 12-x Bi 8+x Se 34 The Pb5Sb 12+x Bi 6-x Se 32 In the case where 0 ≤ x ≤ 5, Pb5Sb 12+x Bi 6-x Se 32 The number of diagonal octahedrons in the NaCl structural unit forming layer is 8; the Pb4Sb 12-x Bi 8+x Se 34 In the given condition, 0 ≤ x ≤ 6, Pb4Sb 12-x Bi 8+ x Se 34 The number of diagonal octahedrons in the NaCl structural unit forming layer is 8.

[0006] Preferably, the Pb5Sb 12+x Bi 6-x Se 32 In the Pb4Sb, x represents 0, 1, 2, 3, or 4; 12-x Bi 8+x Se 34 In the given information, x represents 0, 1, 2, 3, 4, or 5.

[0007] Preferably, the Pb5Sb 12+x Bi 6-x Se 32 and Pb4Sb 12-x Bi 8+x Se 34 The crystal structures of all of them are monoclinic, and the space group is C 2 / m The Pb5Sb 12+x Bi 6-x Se 32 Cell parameters are a =28.032-28.067 Å, b =4.1109-4.1166 Å, c =21.149-21.187 Å, β = 130.700°-130.739°; the Pb4Sb 12-x Bi 8+x Se 34 Cell parameters are a =28.025-28.073 Å, b =4.110-4.131 Å, c =15.678-15.724 Å, β= 115.309°-115.487°.

[0008] A method for preparing a silver-bismuth sulfide-structured thermoelectric material specifically includes the following steps:

[0009] S1. Prepare raw materials: Pb strips, Sb granules, Bi granules, and Se granules;

[0010] S2. Weigh out elements Pb, Sb, Bi, and Se according to atomic ratios, pour them into a quartz tube, seal the quartz tube under vacuum using an oxyhydrogen flame, and obtain Pb₅Sb after a high-temperature solid-state reaction. 12+x Bi 6-x Se 32 or Pb4Sb 12-x Bi 8+x Se 34 Material;

[0011] S3, Pb5Sb obtained from high-temperature solid-state reaction are respectively... 12+x Bi 6-x Se 32 or Pb4Sb 12-x Bi 8+x Se 34 The material is ground into powder, the resulting powder is filled into a graphite mold, and then subjected to discharge plasma sintering to obtain Pb5Sb. 12+x Bi 6-x Se 32 or Pb4Sb 12-x Bi 8+x Se 34 Bulk materials.

[0012] Preferably, in step S2, the specific process of the high-temperature solid-state reaction is as follows: the temperature is raised to 1050°C over 10 hours, held at this temperature for 20 hours, and then quenched with water to obtain Pb5Sb. 12+x Bi 6-x Se 32 or Pb4Sb 12-x Bi 8+x Se 34 Material.

[0013] Preferably, in step S3, the specific process of discharge plasma sintering is as follows: the vacuum degree of the furnace cavity is less than 8 Pa, the axial pressure is 40 MPa, the sintering temperature is 350-400℃, and the sintering time is 12 min; after the discharge plasma sintering is completed, the furnace is cooled to room temperature and the pressure is gradually removed.

[0014] Compared with the prior art, the present invention utilizes the high tolerance of cation sites in silver-bismuth sulfide structural compounds to obtain a multi-component silver-bismuth sulfide structural compound Pb5Sb. 12+x Bi6-x Se 32 and Pb4Sb 12-x Bi 8+x Se 34 Belonging to C / 2 m The space group, with a calculated band gap of around 0.27 eV, is a potential thermoelectric material.

[0015] Existing silver bismuth sulfide-structured compounds, while exhibiting low lattice thermal conductivity, also have relatively low electrical conductivity, and these materials are intrinsically... ZT The values ​​are usually not high. In contrast, this invention yields single-phase compounds, such as Pb5Sb. 12 Bi6Se 32 and Pb4Sb9Bi 11 Se 34 It possesses a specific space group structure and phase parameters, belonging to the silver bismuth sulfide compound family. The obtained Pb4Sb9Bi... 11 Se 34 The material possesses an intrinsic thermoelectric figure of merit of 0.48, exhibiting a high intrinsic thermoelectric figure of merit. The synthesis method of this invention is simple and low-cost. A polycrystalline sample is obtained through a high-temperature solid-state reaction, and the sample is then ground to obtain a powder sample. Furthermore, a plasma rapid sintering process can be combined to obtain a dense polycrystalline bulk material. The synthesized sample has a uniform composition, and the actual proportions of each element in the thermoelectric material are close to the nominal proportions; the difference between the measured and nominal values ​​is essentially negligible.

[0016] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0017] 1. This invention realizes the construction of multi-component silver bismuth sulfide structure compounds. The principle lies in changing the cations and anions, thereby changing the thickness of the NaCl structural unit forming layer. This is a new strategy, different from simple cation substitution.

[0018] 2. This invention can form stable Pb5Sb 12+x Bi 6-x Se 32 and Pb4Sb 12-x Bi 8+x Se 34 Single-phase, such as Pb5Sb 12 Bi6Se 32 and Pb4Sb9Bi 11 Se 34。

[0019] 3. The preparation method of this invention employs a rapid and low-cost high-temperature solid-state reaction synthesis, combined with discharge plasma sintering, to quickly obtain large-scale dense Pb5Sb. 12+x Bi6-x Se 32 and Pb4Sb 12-x Bi 8+x Se 34 This invention utilizes thermoelectric materials, avoiding the shortcomings of traditional solvothermal synthesis methods that require stringent conditions. It employs discharge plasma sintering, with a sintering time not exceeding 12 minutes, offering a rapid process.

[0020] 4. The Pb4Sb9Bi obtained by this invention 11 Se 34 The material has an intrinsic thermoelectric figure of merit of 0.48 and can be used as a thermoelectric material. Attached Figure Description

[0021] Figure 1 Pb5Sb is a thermoelectric material with a bismuth-argentite structure. 12 Bi6Se 32 Structural diagram;

[0022] Figure 2 Pb4Sb9Bi is a thermoelectric material with a bismuth-argentite structure. 11 Se 34 Structural diagram;

[0023] Figure 3 Pb5Sb 12 Bi6Se 32 and Pb4Sb9Bi 11 Se 34 Powder X-ray diffraction pattern of thermoelectric materials;

[0024] Figure 4 Pb5Sb 12 Bi6Se 32 Backscattered electron image of a cross section of thermoelectric material SPS under scanning electron microscopy (SEM); the table shown in the lower right corner of the image represents the elemental percentages.

[0025] Figure 5 Pb4Sb9Bi 11 Se 34 Backscattered electron image of a cross section of thermoelectric material SPS under scanning electron microscopy (SEM); the table shown in the lower right corner of the image represents the elemental percentages.

[0026] Figure 6 Pb5Sb 12 Bi6Se 32 Curves showing the electrical conductivity and Seebeck coefficient of thermoelectric materials as a function of temperature;

[0027] Figure 7 Pb5Sb 12 Bi6Se 32Curves showing the thermal conductivity and thermoelectric figure of merit of thermoelectric materials as a function of temperature;

[0028] Figure 8 Pb4Sb9Bi 11 Se 34 Curves showing the electrical conductivity and Seebeck coefficient of thermoelectric materials as a function of temperature;

[0029] Figure 9 Pb4Sb9Bi 11 Se 34 Curves showing the thermal conductivity and thermoelectric figure of merit of thermoelectric materials as a function of temperature. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0032] Prepare raw materials: Pb strips, Sb granules, Bi granules, and Se granules. The purity of the Pb strips is 99.99% (Beijing Haoke Technology Co., Ltd.), the purity of the Sb granules is 99.99% (Hebei Luohong Technology Co., Ltd.), the purity of the Bi granules is 99.99% (Hebei Luohong Technology Co., Ltd.), and the purity of the Se granules is 99.99% (Hebei Luohong Technology Co., Ltd.).

[0033] See Figures 1 to 9 .

[0034] Example 1 Pb 5 Sb 12 Bi 6 Se 32 Preparation

[0035] (1) According to Pb5Sb 12 Bi6Se 32 The atomic ratios of elemental Pb, Bi, Sb, and Se were measured. The weighing balance used in this embodiment has an error range of ±0.0005g. The initially weighed raw materials were placed in a quartz tube, and the mixture was heated under a vacuum of less than 10... -4 Sealed under Pa conditions;

[0036] (2) The quartz tube sealed in step (1) is placed in a muffle furnace for a high-temperature solid-state reaction. The specific procedure is to raise the temperature to 1050℃ in 10 hours, hold it at this temperature for 20 hours, and then quench it with water to obtain the silver bismuth sulfide structure thermoelectric material Pb5Sb. 12 Bi6Se 32 .

[0037] (3) The silver bismuth sulfide structure thermoelectric material Pb5Sb obtained in step (2) 12 Bi6Se 32 The material is ground into powder, filled into a graphite mold, and then subjected to electrostatic discharge (ESD) sintering. The sintering conditions are: furnace vacuum less than 8 Pa, axial pressure 40 MPa, rapid heating to 400°C, followed by slow cooling to room temperature. During this process, the furnace cools to room temperature while the pressure is gradually reduced. Finally, axial pressure is applied to the mold for demolding, yielding a dense bulk Pb₅Sb. 12 Bi6Se 32 Thermoelectric materials.

[0038] Silver bismuth sulfide structure thermoelectric material Pb5Sb 12+x Bi 6-x Se 32 The crystal structure was obtained by data acquisition using a single-crystal diffractometer and analysis using OLEX 2.5. Silver bismuth sulfide structure thermoelectric material Pb₅Sb 12+x Bi 6-x Se 32 The crystal structure is monoclinic, and the space group is C / 2 m The unit cell parameters are respectively a =28.032-28.067 Å, b =4.1109-4.1166 Å, c =21.149-21.187 Å, β = 130.700°-130.739°, the molecular weight of the crystal is 596.42-629.03 g / mol, and the volume of the crystal is V=1847.7-1854.8 Å. 3 .

[0039] Example 2 Pb 4 Sb 9 Bi 11 Se 34 Preparation

[0040] (1) According to Pb4Sb9Bi 11 Se 34The atomic ratios of elemental Pb, Bi, Sb, and Se were measured. The weighing balance used in this embodiment has an error range of ±0.0005g. The initially weighed raw materials were placed in a quartz tube, and the mixture was heated under a vacuum of less than 10... -4 Sealed under Pa conditions;

[0041] (2) The quartz tube sealed in step (1) is placed in a muffle furnace for a high-temperature solid-state reaction. The specific procedure is to raise the temperature to 1050℃ in 10 hours, hold it at this temperature for 20 hours, and then quench it with water to obtain the silver bismuth sulfide structure thermoelectric material Pb4Sb9Bi. 11 Se 34 .

[0042] (3) The silver bismuth sulfide structure thermoelectric material Pb4Sb9Bi obtained in step (2) 11 Se 34 The material is ground into powder, filled into a graphite mold, and then subjected to discharge plasma sintering. The sintering conditions are: furnace vacuum less than 8 Pa, axial pressure 40 MPa, rapid heating to 400℃, followed by slow cooling to room temperature. During this process, the furnace cools to room temperature while the pressure is gradually reduced. Finally, axial pressure is applied to the mold for demolding, yielding a dense bulk Pb4Sb9Bi. 11 Se 34 Thermoelectric materials.

[0043] Silver bismuth sulfide structure thermoelectric material Pb4Sb 12-x Bi 8+x Se 34 The crystal structure was obtained by data acquisition using a single-crystal diffractometer and analysis using OLEX 2.5. The silver bismuth sulfide structure thermoelectric material Pb₄Sb 12-x Bi 8+x Se 34 The crystal structure is monoclinic, and the space group is C / 2 m The unit cell parameters are respectively a =28.025-28.073 Å, b =4.110-4.131 Å, c =15.678-15.724 Å, β =115.309°-115.487°, the molecular weight of the crystal is 664.16-706.88 g / mol, and the volume of the crystal is V = 1632.45(13)-1645.93(17) Å. 3 .

[0044] Performance testing:

[0045] (1) First, weigh out 0.5 g of Pb5Sb. 12 Bi6Se32 and Pb4Sb9Bi 11 Se 34 (Prepared in Examples 1 and 2), the compound was then ground into a powder sample using an agate mortar and pestle, and powder X-ray diffraction analysis was performed, such as... Figure 1 As shown.

[0046] (2) The electrical properties of the silver-bismuth sulfide-structured thermoelectric materials prepared in Examples 1-2 were tested using a ZEM-3 ULVAC, Inc. (Japan). The relationships between conductivity and Seebeck coefficient as a function of temperature were also obtained, such as... Figure 6 and Figure 8 As shown.

[0047] (3) The thermal diffusivity of the silver-bismuth sulfide structure thermoelectric materials prepared in Examples 1-2 was measured using a Netzsch LFA 467 laser flare thermal conductivity meter. D Tests were conducted, and the thermal conductivity was measured. κ = C p D ρ is calculated to obtain the density. ρ Specific heat was obtained through Archimedes' method. C p Calculated using the Duron-Petty formula. The relationship between thermal conductivity and temperature is as follows: Figure 7 and Figure 9 As shown.

[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 silver bismuth sulphide mineral structure thermoelectric material characterised in that: The silver bismuth sulfide mineral structure thermoelectric material has a chemical formula of Pb5Sb 12+x Bi 6-x Se 32 ; the Pb5Sb 12+x Bi 6-x Se 32 , wherein 0<=x<=5, the Pb5Sb 12+x Bi 6-x Se 32 NaCl structure unit forms a layer, and the number of diagonal octahedrons is 8. Pb5Sb 12+x Bi 6-x Se 32 The crystal structure belongs to monoclinic structure, and the space group is C 2 / m ; the Pb5Sb 12+x Bi 6-x Se 32 The cell parameters are a = 28.032-28.067 Å, b = 4.1109-4.1166 Å, c = 21.149-21.187 Å, β = 130.700°-130.739°; The Pb5Sb 12+x Bi 6-x Se 32 The preparation method specifically comprises the following steps: S1, preparing raw materials Pb strip, Sb particle, Bi particle and Se particle; S2, elemental Pb, Sb, Bi and Se are weighed according to atomic proportions, poured into a quartz tube, vacuumized, and the quartz tube is sealed by using a hydrogen-oxygen flame, and Pb5SbBiSe is obtained after high-temperature solid-phase reaction 12+x Bi 6-x Se 32 material; S3, Pb5Sb obtained by high-temperature solid-phase reaction 12+x Bi 6-x Se 32 The material is ground into powder, the obtained powder is filled into a graphite mold, and then discharge plasma sintering is performed to obtain Pb5Sb 12+x Bi 6-x Se 32 Bulk material.

2. A silver bismuth sulphide mineral structure thermoelectric material as claimed in claim 1 characterised by: Pb5Sb 12+x Bi 6-x Se 32 wherein x is 0, 1, 2, 3 or 4, respectively.

3. A method of producing a silver bismuth sulphide mineral structure thermoelectric material as claimed in any one of claims 1-2, characterised by, Specifically comprising the following steps: S1, preparing raw materials Pb strip, Sb particle, Bi particle and Se particle; S2, elemental Pb, Sb, Bi and Se are weighed according to atomic proportions, poured into a quartz tube, and after vacuumizing, the quartz tube is sealed by hydrogen-oxygen flame, and after high-temperature solid-phase reaction, Pb5SbBiSe is obtained 12+x Bi 6-x Se 32 material; S3, Pb5Sb obtained by high-temperature solid-phase reaction 12+x Bi 6-x Se 32 The material is ground into powder, the obtained powder is filled into a graphite mold, and then discharge plasma sintering is performed to obtain Pb5Sb 12+x Bi 6-x Se 32 Bulk material.

4. A method of producing a silver bismuth sulphide mineral structure thermoelectric material as claimed in claim 3, characterised in that, In step S2, the specific process of high-temperature solid-phase reaction is as follows: 10 hours to 1050 °C, keeping the temperature for 20 h, water quenching, and obtaining Pb5Sb 12+x Bi 6-x Se 32 material.

5. A method of producing a silver bismuth chalcopyrite structure thermoelectric material as claimed in claim 3, wherein In step S3, the specific process of the discharge plasma sintering is as follows: the vacuum degree of the furnace cavity is less than 8 Pa, the axial pressure is 40 MPa, the sintering temperature is 350-400 ℃, and the sintering time is 12 min; after the discharge plasma sintering is completed, the furnace cooling chamber is used to cool to room temperature and the pressure is gradually removed.

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