An intrinsic low-thermal-conductivity n-type pb-bi-s-based thermoelectric material and a preparation method thereof
By preparing Pb3Bi2S6+x thermoelectric materials, the problems of high thermal conductivity and high cost were solved, realizing low-cost, high-performance thermoelectric materials and expanding the application range of thermoelectric materials.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-13
- Publication Date
- 2026-03-17
AI Technical Summary
Existing thermoelectric materials suffer from high thermal conductivity and high cost, making it difficult to achieve efficient energy conversion. Furthermore, the raw materials for traditional thermoelectric materials are scarce, hindering their large-scale application.
A novel N-type Pb-Bi-S-based thermoelectric material, Pb3Bi2S6+x, was developed. By adjusting the molar ratio of Pb, Bi, and S, a bulk material with intrinsically low thermal conductivity was prepared. The electrical transport performance was optimized by combining high-temperature melting and hot-pressing sintering processes.
This has led to the development of low-cost, high-performance thermoelectric materials, which have improved electrical conductivity and power factor, reduced carrier concentration, enhanced thermoelectric performance in the mid-to-low temperature range, and expanded the application range of thermoelectric materials.
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Figure CN117700228B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermoelectric materials technology, and in particular to an intrinsically low thermal conductivity N-type Pb-Bi-S-based thermoelectric material and its preparation method. Background Technology
[0002] Constrained by energy problems, a large portion of traditional fossil fuels is wasted as waste heat, leading to a growing energy and environmental crisis. To alleviate these crises, thermoelectric materials have attracted widespread attention due to their ability to convert heat into electricity without pollution emissions. Thermoelectric conversion efficiency is determined by the dimensionless quality factor (ZT) of the material; the higher the ZT value and / or average ZT value, the higher the conversion efficiency. The ZT value of a material is related to its inherent properties and can be expressed as ZT = (S... 2 σT) / (κ ele +κ lat ), where S, σ, T, κ ele and κ lat represents the Seebeck coefficient, electrical conductivity, operating temperature, electronic thermal conductivity, and lattice thermal conductivity, respectively. Clearly, excellent thermoelectric materials require high electrical transport properties and low thermal conductivity, but the coupling of electrical and thermal transport properties makes it difficult to achieve high ZT values.
[0003] The discovery of intrinsically low thermal conductivity materials can effectively solve this problem, requiring a focus on improving their electrical transport properties. In summary, developing new intrinsically low thermal conductivity materials and exploring strategies to optimize their electrical transport properties are effective ways to obtain high-performance thermoelectric materials. From the overall trend of materials research, it is also necessary to consider both the abundance of materials and production costs. For example, the abundance of Te is only 0.001 ppm, and the raw material costs of thermoelectric materials such as PbTe, GeTe, and Bi₂Te₃ are high, making large-scale use difficult. Most existing research focuses on optimizing their mechanical strength and machinability. In conclusion, there is an urgent need to develop intrinsically low thermal conductivity thermoelectric materials that are low-cost, easily machinable, and abundant in elemental reserves, which will contribute to the widespread application of thermoelectric materials. Summary of the Invention
[0004] To address the aforementioned problems, this invention aims to provide a novel Pb3Bi2S6 structure with intrinsically low lattice thermal conductivity. Based on this new structure, an N-type thermoelectric material and a method for improving its thermoelectric performance are obtained, while also possessing advantages such as abundant raw materials and low cost. When the carrier concentration of Pb3Bi2S6 is reduced, its thermoelectric performance is improved, making it a promising new thermoelectric material.
[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an N-type Pb-Bi-S based thermoelectric material, characterized in that the chemical formula of the bulk material is Pb3Bi2S. 6+x , where 0.0≤x≤0.03.
[0006] Application of an N-type Pb-Bi-S matrix bulk material as a thermoelectric refrigeration material.
[0007] A method for preparing an N-type Pb-Bi-S based bulk material, characterized by comprising the following steps:
[0008] 1) Using Pb, Bi, and S with a purity of not less than 99.9% as initial raw materials, prepare the chemical formula Pb3Bi2S. 6+x Weigh each component raw material according to the ingredient ratio and mix them evenly for later use;
[0009] 2) The mixed raw materials obtained in step 1) are encapsulated in a vacuum quartz tube and subjected to high-temperature melting synthesis;
[0010] 3) Melt-synthesized Pb3Bi2S 6+x The bulk material was ground into powder and then sieved to obtain Pb3Bi2S. 6+x Uniform powder of the matrix material;
[0011] 4) Place the sieved powder from step 3) into a graphite mold and sinter it in a hot press furnace to obtain Pb3Bi2S. 6+x Bulk materials.
[0012] Furthermore, in step 1), the molar ratio of Pb, Bi and S is 3:2:6.0 to 6.03.
[0013] Furthermore, in step 2), the melt synthesis process of the mixed raw materials is as follows:
[0014] (1) Heat from room temperature to 450℃ at a rate of 70-100℃ / h;
[0015] (2) Continue to raise the temperature to 900-1200℃ at a rate of 100-150℃ / h, and keep it at that temperature for 10-12h;
[0016] (3) Allow to cool naturally to room temperature.
[0017] Furthermore, in step 3), the material ground into powder is sieved through a 160-200 mesh sieve to obtain powder with uniform particle size.
[0018] Furthermore, in step 4), the sintering conditions are:
[0019] The vacuum level is 2–4 Pa;
[0020] The sintering temperature is 350–500℃;
[0021] The heat preservation time is 7-10 minutes;
[0022] The sintering pressure is 35–50 MPa;
[0023] The heating rate is 50–100 °C / min.
[0024] A method for improving the hotspot performance of N-type Pb-Bi-S based thermoelectric materials, characterized in that, in the N-type Pb-Bi-S based thermoelectric material prepared according to any one of claims 3-8, the N-type Pb3Bi2S is controlled by adjusting the molar ratio of Pb, Bi, and S. 6+x The thermoelectric properties of bulk materials are improved by adjusting their electrical conductivity, thermal conductivity, Seebeck coefficient, and carrier concentration.
[0025] The beneficial effects of this invention are: it provides a novel N-type Pb-Bi-S intrinsically low thermal conductivity bulk material, Pb3Bi2S6, along with its preparation and thermoelectric performance optimization methods. By adjusting the ratio of Pb, Bi, and S, its electrical conductivity and power factor are improved, thereby enhancing its thermoelectric performance. Specifically, this patent proposes a novel Pb-Bi-S-based intrinsically low thermal conductivity structure, Pb3Bi2S6, which is a highly promising high-performance thermoelectric material. Considering that the vapor pressure of S is relatively high and it is easily volatile during the preparation of this new material, resulting in S vacancies in the obtained Pb3Bi2S6, exhibiting high intrinsic N-type carrier transport characteristics, the thermoelectric performance optimization method provided by this invention suppresses S vacancies by compensating for S elements, reducing the carrier concentration of Pb3Bi2S6, improving the material's electrical transport performance, and thus optimizing its thermoelectric performance.
[0026] This invention provides a novel intrinsically low thermal conductivity material with high-performance thermoelectric material characteristics, expanding the available thermoelectric material systems and offering more possibilities for obtaining high-performance thermoelectric materials. Furthermore, the material's advantages, such as abundant raw materials and low cost, will help promote the widespread application of thermoelectric materials. Attached Figure Description
[0027] Figure 1 Pb3Bi2S prepared for embodiments of the present invention 6+x XRD pattern of bulk material.
[0028] Figure 2 Pb3Bi2S prepared for embodiments of the present invention 6+x Electrical conductivity test results for bulk materials.
[0029] Figure 3 Pb3Bi2S prepared for embodiments of the present invention6+x Seebeck coefficient test chart for bulk materials.
[0030] Figure 4 Pb3Bi2S prepared for embodiments of the present invention 6+x Power factor test chart for bulk materials.
[0031] Figure 5 Pb3Bi2S prepared for embodiments of the present invention 6+x Total thermal conductivity test chart for bulk materials.
[0032] Figure 6 Pb3Bi2S prepared for embodiments of the present invention 6+x Graph of lattice thermal conductivity of bulk materials.
[0033] Figure 7 Pb3Bi2S prepared for embodiments of the present invention 6+x ZT value test chart for bulk materials. Detailed Implementation
[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.
[0035] Example 1
[0036] Pb3Bi2S 6+x In the preparation of bulk materials, x = 0.0 in this embodiment.
[0037] Step 1: Using high-purity (purity ≥ 99.9%) Pb, Bi and S as initial raw materials, Pb:Bi:S = 3:2:6.0 molar ratio, weigh the Pb, Bi and S elements and mix them in a quartz tube, then vacuum seal the tube.
[0038] Step 2: Place the sealed quartz tube into the muffle furnace, set the heating program, and begin heating. The heating program is as follows:
[0039] First, raise the temperature to 450℃ at a rate of 80℃ / h, then continue to raise the temperature to 1150℃ at a rate of 150℃ / h, hold for 12 hours, and then allow it to cool naturally to room temperature.
[0040] Step 3: Melt the Pb3Bi2S obtained at high temperature 6+x The (x=0.0) block was ground and then sieved through a 200-mesh sieve to obtain a powder with uniform particles.
[0041] Step 4: Obtain the Pb3Bi2S 6+x(x=0.0) The powder was loaded into a graphite mold with a diameter of 15mm (the graphite mold is used to sinter the powder sample under high pressure to obtain a dense bulk material), and then placed in a hot press sintering furnace for sintering. The vacuum degree of the sintering environment was 5Pa.
[0042] The sintering temperature was 450℃, the holding time was 7min, the sintering pressure was 50MPa, and the heating rate was 100℃ / min.
[0043] The final Pb3Bi2S 6+x (x=0.0) block.
[0044] Example 2
[0045] Pb3Bi2S 6+x In the preparation of bulk materials, x = 0.01 in this embodiment.
[0046] Step 1: Using high-purity (purity ≥ 99.9%) Pb, Bi and S as initial raw materials, Pb:Bi:S = 3:2:6.0 molar ratio, weigh the Pb, Bi and S elements and mix them in a quartz tube, then vacuum seal the tube.
[0047] Step 2: Place the sealed quartz tube into the muffle furnace, set the heating program, and begin heating. The heating program is as follows:
[0048] First, raise the temperature to 450℃ at a rate of 80℃ / h, then continue to raise the temperature to 1150℃ at a rate of 150℃ / h, hold for 12 hours, and then allow it to cool naturally to room temperature.
[0049] Step 3: Melt the Pb3Bi2S obtained at high temperature 6+x The (x=0.01) block was ground and then sieved through a 180-mesh sieve to obtain a powder with uniform particles.
[0050] Step 4: Obtain the Pb3Bi2S 6+x (x=0.01) The powder was loaded into a graphite mold with a diameter of 15mm and placed in a hot press sintering furnace for sintering. The vacuum degree of the sintering environment was 5Pa.
[0051] The sintering temperature was 450℃, the holding time was 7min, the sintering pressure was 50MPa, and the heating rate was 100℃ / min.
[0052] Finally, Pb3Bi2S was obtained. 6+x (x=0.01) block.
[0053] Example 3
[0054] Pb3Bi2S 6+x In the preparation of bulk materials, x = 0.02 in this embodiment.
[0055] Step 1: Using high-purity (≥99.9%) Pb, Bi and S as initial raw materials, Pb:Bi:S = 3:2:6.03 molar ratio, weigh the Pb, Bi and S elements and mix them in a quartz tube, then vacuum seal the tube.
[0056] Step 2: Place the sealed quartz tube into the muffle furnace, set the heating program, and begin heating. The heating program is as follows:
[0057] First, raise the temperature to 450℃ at a rate of 80℃ / h, then continue to raise the temperature to 1150℃ at a rate of 150℃ / h, hold for 12 hours, and then allow it to cool naturally to room temperature.
[0058] Step 3: Melt the Pb3Bi2S obtained at high temperature 6+x The (x=0.02) block was ground and then sieved through a 160-200 mesh sieve to obtain powder with uniform particle size.
[0059] Step 4: Obtain the Pb3Bi2S 6+x (x=0.02) The powder was loaded into a graphite mold with a diameter of 15mm and placed in a hot press sintering furnace for sintering. The vacuum degree of the sintering environment was 5Pa.
[0060] The sintering temperature was 450℃, the holding time was 7min, the sintering pressure was 50MPa, and the heating rate was 100℃ / min.
[0061] Finally, Pb3Bi2S was obtained. 6+x (x=0.02) block.
[0062] Example 4
[0063] Pb3Bi2S 6+x In the preparation of bulk materials, x = 0.03 in this embodiment.
[0064] Step 1: Using high-purity (≥99.9%) Pb, Bi and S as initial raw materials, Pb:Bi:S = 3:2:6.03 molar ratio, weigh the Pb, Bi and S elements and mix them in a quartz tube, then vacuum seal the tube.
[0065] Step 2: Place the sealed quartz tube into the muffle furnace, set the heating program, and begin heating. The heating program is as follows:
[0066] First, raise the temperature to 450℃ at a rate of 80℃ / h, then continue to raise the temperature to 1150℃ at a rate of 150℃ / h, hold for 12 hours, and then allow it to cool naturally to room temperature.
[0067] Step 3: Melt the Pb3Bi2S obtained at high temperature6+x The (x=0.02) block was ground and then sieved through a 200-mesh sieve to obtain a uniform powder.
[0068] Step 4: Obtain the Pb3Bi2S 6+x (x=0.03) The powder was loaded into a graphite mold with a diameter of 15mm and placed in a hot press sintering furnace for sintering. The vacuum degree of the sintering environment was 5Pa.
[0069] The sintering temperature was 450℃, the holding time was 7min, the sintering pressure was 50MPa, and the heating rate was 100℃ / min.
[0070] The Pb3Bi2S obtained in Examples 1-4 6+x The thermoelectric transport properties of the bulk material were tested and analyzed, and the specific analysis is as follows:
[0071] The Pb3Bi2S obtained in Examples 1-4 6+x The bulk material is cut into regular cuboids and square slices, and the surface is sanded with sandpaper before thermoelectric performance testing is performed. The thermoelectric performance includes electrical conductivity (σ) and Seebeck coefficient (S).
[0072] Based on the measured data, through the power factor (PF = S) 2 The electrical properties of materials are evaluated using σ). Figure 1 Pb3Bi2S 6+x The comparison between the powder XRD and the simulated peak positions shows that the above preparation method successfully obtained a pure phase material, which conforms to the characteristics of the new structure.
[0073] Figure 2-4 They are Pb3Bi2S 6+x Electrical conductivity (σ), Seebeck coefficient (S), and power factor (PF = S) of bulk materials 2 σ). It can be seen that as the sulfur content increases, the conductivity gradually decreases (σ). Figure 2 The absolute value of the Seebeck coefficient gradually increases. Figure 3 This indicates that the increase in sulfur can compensate for sulfur vacancies, effectively reducing carrier concentration and ultimately improving the power factor in the mid-to-low temperature region. Figure 4 At x = 0.03, the power factor ranges from 423 K to ~1.0 μW / cm². -1 K -2 Increased to ~1.6μWcm -1 K -2 .
[0074] In addition, based on the thermal diffusivity (D) and specific heat capacity (C) p From the density (ρ) of the material, the total thermal conductivity (κ) of the material can be obtained.tot =D·C p ·ρ) and lattice thermal conductivity (κ) lat =κ tot –L·σ·T) as Figure 5 and Figure 6 As shown, L is the Lorentz constant, which can be obtained from the Seebeck coefficient. It can be seen that the total thermal conductivity of Pb3Bi2S6 at room temperature is 0.85 W / m². -1 K -1 The lattice thermal conductivity is 0.66 W / m². -1 K -1 Pb₃Bi₂S₆ exhibits a room-temperature lattice thermal conductivity similar to other intrinsically low thermal conductivity materials, thus classifying it as a novel intrinsically low thermal conductivity material. Furthermore, with the increase of sulfur content, the lattice thermal conductivity in the high-temperature region is further reduced.
[0075] The increase in power factor and the decrease in thermal conductivity led to an increase in ZT value. Figure 7 Pb3Bi2S is given 6+x ZT value of thermoelectric materials (ZT = S) 2 σT / κ tot The ZT value of Pb3Bi2S6 gradually increases with increasing temperature, from 0.02 at 300 K to a peak of 0.31 at 723 K. By reducing the carrier concentration, the electrical transport performance at medium and low temperatures is improved, thus achieving an increase in the ZT value in the medium and low temperature range. The average ZT value from 300 to 673 K increases from 0.07 for Pb3Bi2S6 to [missing value]. 6.01 0.11.
[0076] A novel N-type material, Pb3Bi2S6, with intrinsically low thermal conductivity, was synthesized via high-temperature melting and hot-pressing sintering, representing a promising high-performance thermoelectric material. Further optimization of the thermoelectric properties of Pb3Bi2S6 by adjusting the molar ratio of Pb, Bi, and S further revealed its advantages, including good mechanical properties, abundant raw material reserves, and low cost, demonstrating significant application potential in high-performance thermoelectric and thermal resistance materials.
[0077] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Various changes and modifications can be made to the present invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.
Claims
1. A method for producing an N-type Pb-Bi-S-based bulk material, characterized by, The method comprises the following steps: 1) As initial raw materials, Pb, Bi and S having a purity of not less than 99.9% are weighed according to the composition ratio of the chemical formula Pb3Bi2S6 to prepare a raw material mixture, and are uniformly mixed to prepare a raw material mixture. 6+x 1) As initial raw materials, Pb, Bi and S having a purity of not less than 99.9% are weighed according to the composition ratio of the chemical formula Pb3Bi2S6 to prepare a raw material mixture, and are uniformly mixed to prepare a raw material mixture. 2) The mixed raw materials obtained in step 1) are sealed in a vacuum quartz tube and subjected to high-temperature melting synthesis; 3) The Pb3Bi2S6 bulk material is ground to a powder and sieved to obtain a uniform powder of the Pb3Bi2S6 base material; 6+x The Pb3Bi2S6 bulk material is ground to a powder and sieved to obtain a uniform powder of the Pb3Bi2S6 base material; 6+x The Pb3Bi2S6 bulk material is ground to a powder and sieved to obtain a uniform powder of the Pb3Bi2S6 base material; 4) Put the sieved powder of step 3) into a graphite mold and put it into a hot-pressing sintering furnace for sintering to obtain Pb3Bi2S 6+x Bulk material; wherein 0.0 < x < 0.03, the space group of the crystal structure of the material is Cmcm; In step 2), the melting synthesis process of the mixed raw materials is as follows: 1) The temperature is raised from room temperature to 450℃ at a rate of 70-100℃ / h; 2) The temperature is continuously raised to 900-1200℃ at a rate of 100-150℃ / h, and the temperature is maintained for 10-12h; 3) The temperature is naturally cooled to room temperature; In step 4), the hot-pressing sintering conditions are as follows: The vacuum degree is 2-4Pa; The sintering temperature is 350-500℃; The temperature maintaining time is 7-10min; The sintering pressure is 35-50MPa; 2. The method of claim 1, wherein: The temperature raising rate is 50-100℃ / min. In step 3), the material ground into powder is sieved through a 160-200 mesh sieve to obtain a powder with uniform particles.
3. A method for improving the thermoelectric performance of N-type Pb-Bi-S based thermoelectric materials, characterized in that, The N-type Pb-Bi-S based thermoelectric material prepared according to any of the methods of claims 1-2, by adjusting the molar ratio of Pb, Bi and S, the N-type Pb3Bi2S 6+x The electrical conductivity, thermal conductivity, Seebeck coefficient and carrier concentration of the bulk material are improved, so that the thermoelectric performance of the material is improved.