BiSbTe-Pb thermoelectric material compounded with carborane and preparation method of BiSbTe-Pb thermoelectric material

Abstract

The invention discloses a BiSbTe-Pb thermoelectric material compounded with carborane and a preparation method of the BiSbTe-Pb thermoelectric material. The method comprises the following steps: firstly, synthesizing BiSbTe-Pb powder through a solvothermal method, then compounding carborane and BiSbTe-Pb in a rotary evaporation manner to form BiSbTe-Pb powder compounded with carborane, and finally, pressing a powder sample into a BiSbTe-Pb block material compounded with carborane, which is good in compactness, by adopting spark plasma sintering. The synthesis process disclosed by the invention is simple, and the BiSbTe-Pb thermoelectric material compounded with carborane has excellent thermoelectric conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials and relates to a BiSbTe-Pb thermoelectric material composed of carborane and its preparation method. Background Technology

[0002] Thermoelectric energy conversion technology, as a novel green and clean energy technology, enables the direct conversion between electrical and thermal energy, and has become a research hotspot in both industry and academia. This technology relies on the Seebeck effect to generate electricity and the Peltier effect to achieve thermoelectric cooling. It possesses numerous advantages, including flexibility, convenience, safety, reliability, cost control, small size, simple structure, and environmental friendliness, and has broad application prospects in fields such as environmental energy recovery, special power source preparation, and refrigeration equipment development. However, its large-scale commercial application still faces bottlenecks, primarily due to the low thermoelectric conversion efficiency (approximately 10%) and the unresolved fundamental scientific issues related to electroacoustic transport. Therefore, developing high-performance thermoelectric materials with excellent environmental compatibility and deeply exploring their electroacoustic transport mechanisms has significant academic value and practical guiding significance.

[0003] The power generation efficiency of thermoelectric materials depends primarily on their thermoelectric figure of merit zT, which is expressed as zT=(S 2 σ / κ)T, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature. Under specific temperature conditions, the thermoelectric properties of a material exhibit a clear pattern: the larger the Seebeck coefficient, the higher the electrical conductivity, and the lower the thermal conductivity, the better its overall thermoelectric performance. However, the key issue is that these three parameters have a strong mutual coupling effect, making the independent control of a single parameter a significant challenge.

[0004] Bi₂Te₃ is a typical narrow bandgap semiconductor with a bandgap of approximately 0.15 eV. Its complex band structure and unique atomic composition endow the material with excellent combined electrical and thermal transport properties. In recent years, with the innovation of experimental preparation techniques and the continuous deepening of theoretical research, the thermoelectric advantages of the Bi₂Te₃ system have made continuous breakthroughs. In 2015, Kim et al. successfully synthesized Bi₂Te₃ into a nanomaterial with a bandgap of approximately 0.15 eV. 0.5 Sb 1.5The ZT value of Te3 was increased to 1.86, setting a new record for this system. This was achieved by introducing dislocation structures at low-energy grain boundaries through a compacted liquid phase process, which enabled efficient scattering of mid-frequency phonons and thus significantly reduced the lattice thermal conductivity (Kim S I, Lee KH, Mun HA, et al. Dense dislocation arrays embedded in grainboundaries for high-performance bulk thermoelectrics[J]. Science, 2015, 348(6230):109-114.). In 2018, Deng et al. used melt spinning technology to construct ZnTe nanoprecipitates in situ in the Bi2Te3 system, reducing the lattice thermal conductivity to 0.35 W·m while maintaining a high power factor. -1 ·K -1 (This value is close to Bi) 2-x Sb x The theoretical limit of the Te3 system ultimately enabled the material to achieve a high ZT value of 1.4 at 400 K (Deng R, Su X, Hao S, et al. High thermoelectric performance in Bi 0．46 Sb l．54 Te3 nanostructured with ZnTe[J]. Energy & Environmental Science, 2018, 11(6):1520-1535. Although the above studies have improved the performance, they have problems such as poor material mechanical properties, harsh process parameters, and narrow performance adaptation temperature range.

[0005] Carboranes, as a class of uniquely structured organic compounds, possess a rigid cage-like structure that can improve the mechanical properties of materials, excellent thermal and chemical stability, and significant electron-deficient characteristics. They have important applications in coordination chemistry, supramolecular chemistry, nanomaterials, photochemistry, medical science, combustion rate regulators, high-performance fuels, and high-temperature resistant materials. Currently, there are no literature reports on their application in thermoelectric materials. Summary of the Invention

[0006] To overcome the drawbacks of high manufacturing cost and weak mechanical properties of thermoelectric materials, this invention provides a BiSbTe-Pb thermoelectric material composited with carborane and its preparation method. The method involves synthesizing BiSbTe-Pb thermoelectric material via a solvothermal method, then incorporating carborane into the BiSbTe-Pb thermoelectric material using rotary evaporation, and finally pressing the powder sample into a dense bulk material using spark plasma sintering.

[0007] The technical solution adopted in this invention is as follows:

[0008] The preparation method of BiSbTe-Pb thermoelectric material based on carborane is as follows:

[0009] Step 1: Bismuth trichloride, antimony trichloride, tellurium powder, and lead acetate trihydrate are added sequentially to a disodium EDTA-2Na solution at a molar ratio of 0.1–0.6:1.4–1.9:3:0.005–0.009. The mixture is stirred until homogeneous and subjected to a solvothermal reaction at 150–250 °C. After the reaction is complete, the mixture is cooled to room temperature, and the product is removed, centrifuged, washed to remove impurities, and vacuum dried to obtain BiSbTe-Pb powder.

[0010] Step 2: Slowly add a solution of n-butyllithium in hexane to a solution of meta-carborane in diethyl ether. After the addition is complete, stir the mixture at room temperature for 14–20 h. Then add 3-pyridyl isothiocyanate and continue stirring at room temperature for 20–36 h. After the reaction is complete, quench with dilute hydrochloric acid. Finally, evaporate to dryness by rotary evaporation to obtain a powder. The powder is thoroughly washed with dichloromethane and diethyl ether, and then dried under vacuum to obtain carborane m-3-py(C 14 H 20 B 10 N4S2);

[0011] Alternatively, a solution of n-butyllithium in n-hexane is slowly added dropwise to a diethyl ether solution of meta-carborane. After the addition is complete, the mixture is stirred at -90 to -70°C for 0.5 to 2 hours. Then, phenyl isothiocyanate is added at room temperature, and the reaction is continued at room temperature for 20 to 36 hours. After the reaction is complete, dilute hydrochloric acid is added for quenching, the organic phase is separated, the aqueous phase is extracted with diethyl ether, the organic phases are combined, evaporated to dryness by rotary evaporation, and then purified by silica gel column chromatography to obtain carborane ms-ph (C 16 H 22 B 10 N2S2);

[0012] Step 3: Disperse carborane m-3-py or ms-ph and BiSbTe-Pb powder in ethanol at a mass ratio of 0.1 to 0.9:100, stir evenly, and then evaporate to dryness by rotary evaporation to obtain BiSbTe-Pb powder of composite carborane.

[0013] Step 4: The BiSbTe-Pb powder of composite carborane is subjected to discharge plasma sintering (SPS) to obtain a bulk BiSbTe-Pb thermoelectric material of composite carborane.

[0014] Preferably, in step 1, the molar ratio of bismuth trichloride, antimony trichloride, tellurium powder, and lead acetate trihydrate is 0.4:1.6:3:0.008.

[0015] Preferably, in step 1, the solvothermal reaction temperature is 200°C and the reaction time is 12 hours.

[0016] Preferably, in step 1, the washing is performed twice with deionized water and twice with anhydrous ethanol, the centrifugation conditions are 10000 r / min for 3 to 5 min, the vacuum drying temperature is 50℃ to 70℃, and the drying time is 10 to 14 h.

[0017] Preferably, in step 2, the concentration of the n-butyllithium n-hexane solution is 1.4–1.7 mol / L, and the concentration of the meta-carborane diethyl ether solution is 0.05–0.15 mol / L.

[0018] Preferably, in step 2, the molar ratio of n-butyllithium, meta-carborane, 3-pyridyl isothiocyanate or benzene isothiocyanate is 1:1:1.5 to 3.

[0019] Preferably, in step 3, the mass ratio of carborane m-3-py or ms-ph to BiSbTe-Pb powder is 0.1 to 0.7:100.

[0020] Preferably, in step 3, the stirring time is 1 to 2 hours and the rotary evaporation temperature is 58 to 60°C.

[0021] Preferably, in step 4, the sintering temperature of the discharge plasma sintering is 400–500°C, the holding time is 3–7 minutes, and the sintering pressure is 50–70 MPa. In a specific embodiment of the present invention, the sintering temperature is 420°C, the holding time is 5 minutes, and the sintering pressure is 60 MPa.

[0022] The present invention provides a BiSbTe-Pb thermoelectric material of composite carborane prepared by the above preparation method.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The present invention uses solvothermal method and rotary evaporation to realize the composite of carborane and BiSbTe-Pb powder materials. The synthesis process is simple and the time is short. The sintering is carried out by spark plasma sintering technology. Taking advantage of the characteristics of sintering during the pressurization process, the required temperature is lower than that of hot pressing and other molding technologies, and the mechanical properties and density of the sample are better. This improves the production efficiency and reduces the synthesis energy consumption, making it suitable for industrial application.

[0025] (2) This invention combines carborane and BiSbTe-Pb. Carborane acts as a strong electron acceptor, increasing the hole concentration in the material and thus enhancing electrical conductivity. Simultaneously, its rigid cage structure can embed into the lattice formation point defects of BiSbTe, strengthening mid-to-high frequency phonon scattering and thereby suppressing lattice thermal conductivity. The BiSbTe-Pb thermoelectric material prepared by this invention, composed of carborane, achieves the control of three thermoelectric parameters, slightly increasing electrical conductivity, exhibiting a small decrease in the Seebeck coefficient, and significantly reducing thermal conductivity κ, thereby achieving the goal of improving the thermoelectric conversion efficiency of the material. Attached Figure Description

[0026] Figure 1 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The relationship between conductivity and temperature for samples of / x wt%m-3-py (x=0, 0.1, 0.3, 0.5 and 0.7).

[0027] Figure 2 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The Seebeck coefficient of the samples with x wt%m-3-py (x=0, 0.1, 0.3, 0.5 and 0.7) is compared with the temperature.

[0028] Figure 3 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The power factor of the sample with x wt%m-3-py (x=0, 0.1, 0.3, 0.5 and 0.7) is related to the temperature.

[0029] Figure 4 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008The relationship between thermal conductivity κ and temperature for samples of / x wt%m-3-py (x=0, 0.1, 0.3, 0.5 and 0.7).

[0030] Figure 5 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The thermoelectric figure of merit (zT) of the samples with x wt%m-3-py (x=0, 0.1, 0.3, 0.5 and 0.7) versus temperature variation. Detailed Implementation

[0031] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings.

[0032] Example 1

[0033] (1) 120 ml of ultrapure water was added to a polytetrafluoroethylene liner and stirred with a magnetic stirrer. 0.6 g of EDTA-2Na was weighed in air and added to the liner with stirring. Then, 2.4 mmol of BiCl3, 9.6 mmol of SbCl3, and 18 mmol of Te powder were added to the liner. Next, 0.048 mmol of lead acetate trihydrate was added to the liner. Finally, 5 g of sodium hydroxide and 2 g of sodium borohydride were added. The mixture was stirred at room temperature for 1 h and then sealed in a hydrothermal reactor. A solvothermal reaction was carried out at 200 °C for 12 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature. The product was removed and washed twice with deionized water and twice with anhydrous ethanol. The product was centrifuged at 10000 r / min for 3.5 min. Then, it was vacuum dried at 60 °C for 12 h. The sample was then removed and ground to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 powder.

[0034] (2) 144 mg of meta-carborane was dissolved in 10 ml of diethyl ether, and then 0.65 ml of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred continuously at room temperature for 16 h. Subsequently, 0.225 ml of 3-pyridyl isothiocyanate was added to the above system, and the reaction was continued to be stirred at room temperature for 24 h. After the reaction was completed, dilute hydrochloric acid was added to the system for quenching, and finally the mixture was evaporated to dryness to obtain a powder. The powder was washed thoroughly with dichloromethane and diethyl ether in sequence, and then dried under vacuum to obtain carborane m-3-py (C 14 H 20 B 10 N4S2).

[0035] 144 mg of meta-carborane was dissolved in 10 mL of diethyl ether, and then 0.65 mL of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred at -78 °C for 1 hour. Subsequently, 2 mL of phenyl isothiocyanate was added at room temperature, and the reaction was continued with stirring at room temperature for 24 hours. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, and the organic phase was separated. The aqueous phase was extracted with diethyl ether. The combined organic phases were evaporated to dryness by rotary evaporation and then purified by silica gel column chromatography to obtain carborane MS-PH (C 16 H 22 B 10 N2S2).

[0036] (3) Add 0.003 g of carborane ms-ph and 3 g of Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.1wt%ms-ph sample.

[0037] Add 0.003 g m-3-py and 3 g Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.1wt%m-3-py sample.

[0038] (4) Bi respectively 0.4 Sb 1.6 Te3-Pb 0.008 / 0.1wt%ms-ph sample, Bi 0.4 Sb 1.6 Te3-Pb 0.008 A 0.1 wt% m-3-py sample was placed in a specially made graphite mold with an inner diameter of 10 mm and subjected to discharge plasma sintering at a temperature of 420℃ for 5 minutes and a sintering pressure of 60 MPa to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.1wt%ms-ph, Bi 0.4 Sb 1.6 Te3-Pb 0.008 / 0.1wt% ms-py thermoelectric material bulk. Thermoelectric performance testing was conducted perpendicular to the sintering pressure direction.

[0039] Example 2

[0040] (1) 120 ml of ultrapure water was added to a polytetrafluoroethylene liner and stirred with a magnetic stirrer. 0.6 g of EDTA-2Na was weighed in air and added to the liner with stirring. Then, 2.4 mmol BiCl3, 9.6 mmol SbCl3, and 18 mmol Te powder were added to the liner. Next, 0.048 mmol of lead acetate trihydrate was added to the liner. Finally, 5 g of sodium hydroxide and 2 g of sodium borohydride were added. The mixture was stirred at room temperature for 1 h and then sealed in a hydrothermal reactor. A solvothermal reaction was carried out at 200 °C for 12 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature. The product was removed and washed twice with deionized water and twice with anhydrous ethanol. The product was centrifuged at 10000 r / min for 3.5 min. Then, it was vacuum dried at 60 °C for 12 h. The sample was then removed and ground to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 powder.

[0041] (2) 144 mg of meta-carborane was dissolved in 10 ml of diethyl ether, and then 0.65 ml of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred continuously at room temperature for 16 h. Subsequently, 0.225 ml of 3-pyridyl isothiocyanate was added to the above system, and the reaction was continued to be stirred at room temperature for 24 h. After the reaction was completed, dilute hydrochloric acid was added to the system for quenching, and finally the mixture was evaporated to dryness to obtain a powder. The powder was washed thoroughly with dichloromethane and diethyl ether in sequence, and then dried under vacuum to obtain carborane m-3-py (C 14 H 20 B 10 N4S2).

[0042] 144 mg of meta-carborane was dissolved in 10 mL of diethyl ether, and then 0.65 mL of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred at -78 °C for 1 hour. Subsequently, 2 mL of phenyl isothiocyanate was added at room temperature, and the reaction was continued with stirring at room temperature for 24 hours. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, and the organic phase was separated. The aqueous phase was extracted with diethyl ether. The combined organic phases were evaporated to dryness by rotary evaporation and then purified by silica gel column chromatography to obtain carborane MS-PH (C 16 H 22 B 10 N2S2).

[0043] (3) Add 0.009 g of carborane ms-ph and 3 g of Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.3wt%ms-ph sample.

[0044] Add 0.009 g of carborane ms-py and 3 g of Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.3wt%ms-py sample.

[0045] (4) Bi respectively 0.4 Sb 1.6 Te3-Pb 0.008 / 0.3wt%ms-ph sample, Bi 0.4 Sb 1.6 Te3-Pb 0.008 A 0.3wt% ms-py sample was placed in a specially made graphite mold with an inner diameter of 10mm and subjected to discharge plasma sintering at a temperature of 420℃ for 5 minutes and a sintering pressure of 60MPa to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.3wt%ms-ph, Bi 0.4 Sb 1.6 Te3-Pb 0.008 / 0.3wt% ms-py thermoelectric material bulk. Thermoelectric performance tests were conducted perpendicular to the sintering pressure direction.

[0046] Example 3

[0047] (1) 120 ml of ultrapure water was added to a polytetrafluoroethylene liner and stirred with a magnetic stirrer. 0.6 g of EDTA-2Na was weighed in air and added to the liner with stirring. Then, 2.4 mmol BiCl3, 9.6 mmol SbCl3, and 18 mmol Te powder were added to the liner. Next, 0.048 mmol of lead acetate trihydrate was added to the liner. Finally, 5 g of sodium hydroxide and 2 g of sodium borohydride were added. The mixture was stirred at room temperature for 1 h and then sealed in a hydrothermal reactor. A solvothermal reaction was carried out at 200 °C for 12 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature. The product was removed and washed twice with deionized water and twice with anhydrous ethanol. The product was centrifuged at 10000 r / min for 3.5 min. Then, it was vacuum dried at 60 °C for 12 h. The sample was then removed and ground to obtain Bi.0.4 Sb 1.6 Te3-Pb 0.008 powder.

[0048] (2) 144 mg of meta-carborane was dissolved in 10 ml of diethyl ether, and then 0.65 ml of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred continuously at room temperature for 16 h. Subsequently, 0.225 ml of 3-pyridyl isothiocyanate was added to the above system, and the reaction was continued to be stirred at room temperature for 24 h. After the reaction was completed, dilute hydrochloric acid was added to the system for quenching, and finally the mixture was evaporated to dryness to obtain a powder. The powder was washed thoroughly with dichloromethane and diethyl ether in sequence, and then dried under vacuum to obtain carborane m-3-py (C 14 H 20 B 10 N4S2).

[0049] 144 mg of meta-carborane was dissolved in 10 mL of diethyl ether, and then 0.65 mL of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred at -78 °C for 1 hour. Subsequently, 2 mL of phenyl isothiocyanate was added at room temperature, and the reaction was continued with stirring at room temperature for 24 hours. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, and the organic phase was separated. The aqueous phase was extracted with diethyl ether. The combined organic phases were evaporated to dryness by rotary evaporation and then purified by silica gel column chromatography to obtain carborane MS-PH (C 16 H 22 B 10 N2S2).

[0050] (3) Add 0.015 g carborane ms-ph and 3 g Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.5wt%ms-ph sample.

[0051] Add 0.015 g of carborane m-3-py and 3 g of Bi to a rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.5wt%ms-py sample.

[0052] (4) Bi respectively 0.4 Sb 1.6 Te3-Pb 0.008 / 0.5wt%ms-ph sample, Bi 0.4 Sb 1.6 Te3-Pb 0.008 A 0.5wt% ms-py sample was placed in a specially made graphite mold with an inner diameter of 10mm and subjected to discharge plasma sintering at a temperature of 420℃ for 5 minutes and a sintering pressure of 60MPa to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.5wt%ms-ph, Bi 0.4 Sb 1.6 Te3-Pb 0.008 / 0.5wt% ms-py thermoelectric material bulk. Thermoelectric performance tests were conducted perpendicular to the sintering pressure direction.

[0053] Example 4

[0054] (1) 120 ml of ultrapure water was added to a polytetrafluoroethylene liner and stirred with a magnetic stirrer. 0.6 g of EDTA-2Na was weighed in air and added to the liner with stirring. Then, 2.4 mmol BiCl3, 9.6 mmol SbCl3, and 18 mmol Te powder were added to the liner. Next, 0.048 mmol of lead acetate trihydrate was added to the liner. Finally, 5 g of sodium hydroxide and 2 g of sodium borohydride were added. The mixture was stirred at room temperature for 1 h and then sealed in a hydrothermal reactor. A solvothermal reaction was carried out at 200 °C for 12 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature. The product was removed and washed twice with deionized water and twice with anhydrous ethanol. The product was centrifuged at 10000 r / min for 3.5 min. Then, it was vacuum dried at 60 °C for 12 h. The sample was then removed and ground to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 powder.

[0055] (2) 144 mg of meta-carborane was dissolved in 10 ml of diethyl ether, and then 0.65 ml of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred continuously at room temperature for 16 h. Subsequently, 0.225 ml of 3-pyridyl isothiocyanate was added to the above system, and the reaction was continued to be stirred at room temperature for 24 h. After the reaction was completed, dilute hydrochloric acid was added to the system for quenching, and finally the mixture was evaporated to dryness to obtain a powder. The powder was washed thoroughly with dichloromethane and diethyl ether in sequence, and then dried under vacuum to obtain carborane m-3-py (C 14 H 20 B 10 N4S2).

[0056] 144 mg of meta-carborane was dissolved in 10 mL of diethyl ether, and then 0.65 mL of a 1.6 mol / L n-butyllithium solution in n-hexane was slowly added dropwise. After the addition was complete, the reaction mixture was stirred at -78 °C for 1 hour. Subsequently, 2 mL of phenyl isothiocyanate was added at room temperature, and the reaction was continued with stirring at room temperature for 24 hours. After the reaction was completed, dilute hydrochloric acid was added to quench the reaction, and the organic phase was separated. The aqueous phase was extracted with diethyl ether. The combined organic phases were evaporated to dryness by rotary evaporation and then purified by silica gel column chromatography to obtain carborane MS-PH (C 16 H 22 B 10 N2S2).

[0057] (3) Add 0.021 g carborane ms-ph and 3 g Bi to the rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.7wt%ms-ph sample.

[0058] Add 0.021 g of carborane m-3-py and 3 g of Bi to a rotary evaporation flask. 0.4 Sb 1.6 Te3-Pb 0.008 The powder was then mixed with 50 ml of ethanol, stirred for 1 hour, and then rotary evaporated at 58 °C to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.7wt%ms-py sample.

[0059] (4) Bi respectively 0.4 Sb 1.6 Te3-Pb 0.008 / 0.7wt%ms-ph sample, Bi 0.4 Sb 1.6 Te3-Pb 0.008 A 0.7wt% ms-py sample was placed in a specially made graphite mold with an inner diameter of 10mm and subjected to discharge plasma sintering at a temperature of 420℃ for 5 minutes and a sintering pressure of 60MPa to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 / 0.7wt%ms-ph, Bi 0.4 Sb 1.6 Te3-Pb 0.008 / 0.7wt% ms-py thermoelectric material bulk. Thermoelectric performance tests were conducted perpendicular to the sintering pressure direction.

[0060] Comparative Example 1

[0061] 120 ml of ultrapure water was added to a polytetrafluoroethylene (PTFE) liner and stirred magnetically. 0.6 g of EDTA-2Na was weighed in air and added to the liner, followed by stirring. Then, 2.4 mmol BiCl3, 9.6 mmol SbCl3, and 18 mmol Te powder were added to the liner, followed by 0.048 mmol lead acetate trihydrate. Finally, 5 g sodium hydroxide and 2 g sodium borohydride were added. The mixture was stirred at room temperature for 1 hour and then sealed in a hydrothermal reactor. A solvothermal reaction was carried out at 200 °C for 12 hours. After the reaction, the hydrothermal reactor was cooled to room temperature. The product was removed and washed twice each with deionized water and anhydrous ethanol. The product was centrifuged at 10000 r / min for 3.5 min, and then vacuum dried at 60 °C for 12 hours. The sample was then removed, ground, and placed in a specially made graphite mold with an inner diameter of 10 mm. Discharge plasma sintering was performed at 420 °C for 5 minutes and a sintering pressure of 60 MPa to obtain Bi. 0.4 Sb 1.6 Te3-Pb 0.008 Thermoelectric material bulk (BST-Pb). Thermoelectric performance testing was conducted perpendicular to the sintering pressure direction.

[0062] Table 1

[0063] Figure 1 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The conductivity versus temperature curve for samples with x wt% m-3-py (x=0, 0.1, 0.3, 0.5, and 0.7) shows that the BiSbTe-Pb thermoelectric material without carborane composite prepared in Comparative Example 1 has a low conductivity, only 1331 × 10⁻⁶ at 321 K. 4 S / m, and when the recombination amount of m-3-py is 0.3 wt%, a high conductivity of 1.677.32 × 10⁻⁶ was achieved at 321 K. 4 The S / m ratio indicates that the composite carborane can significantly improve the electrical conductivity of the material.

[0064] The Seebeck coefficients of each embodiment and comparative example were tested, and the results are as follows: Figure 2 As shown. From Figure 2It can be seen that, due to the mutual constraint between Seebeck coefficient and conductivity, doped carboranes do not have a significant advantage in Seebeck coefficient.

[0065] Figure 3 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The graph shows the power factor versus temperature for samples with x wt% m-3-py (x=0, 0.1, 0.3, 0.5, and 0.7). It can be seen that, considering both conductivity and Seebeck coefficient, the electrical transport performance of the sample with 0.5 wt% m-3-py composite is significantly higher near 321 K compared to the uncomposite carborane sample, reaching 1.1 times that of the uncomposite sample.

[0066] Figure 4 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The graph shows the relationship between thermal conductivity κ and temperature for samples with m-3-py (x=0, 0.1, 0.3, 0.5, and 0.7) at a concentration of 0.7 wt% m-3-py. It can be seen that the thermal conductivity of the composite carborane samples is significantly lower than that of the uncomposite samples. The uncomposite samples have a thermal conductivity of 1.104 W / m / K at 321 K, while the composite amount of m-3-py at 0.7 wt% achieves a lower thermal conductivity of 0.9027 W / m / K at 321 K. This indicates that the composite carborane can significantly reduce the thermal conductivity of the material.

[0067] Figure 5 Bi in each embodiment and comparative example 0.4 Sb 1.6 Te3-Pb 0.008 / x wt%ms-ph and Bi 0.4 Sb 1.6 Te3-Pb 0.008 The graph shows the relationship between the thermoelectric figure of merit (zT) and temperature for samples with a composite content of 0.5 wt% m-3-py (x=0, 0.1, 0.3, 0.5, and 0.7). It can be seen that when the composite content is 0.5 wt% m-3-py, the highest zT of 1.96 is achieved at 424 K, representing a 25% improvement in thermoelectric performance compared to the uncomposite sample.

Claims

1. A method for preparing BiSbTe-Pb thermoelectric materials with composite carborane, characterized in that, The specific steps are as follows: Step 1: Bismuth trichloride, antimony trichloride, tellurium powder, and lead acetate trihydrate are added sequentially to an EDTA-2Na solution at a molar ratio of 0.1–0.6:1.4–1.9:3:0.005–0.

009. The mixture is stirred until homogeneous and subjected to a solvothermal reaction at 150–250°C. After the reaction is complete, the mixture is cooled to room temperature, and the product is removed, centrifuged, washed to remove impurities, and vacuum dried to obtain BiSbTe-Pb powder. Step 2: Slowly add n-butyllithium in hexane to the diethyl ether solution of meta-carborane. After the addition is complete, stir the mixture at room temperature for 14-20 h. Then add 3-pyridyl isothiocyanate and continue stirring at room temperature for 20-36 h. After the reaction is complete, add dilute hydrochloric acid to quench the reaction. Finally, evaporate the mixture to dryness to obtain powder. Wash the powder thoroughly with dichloromethane and diethyl ether in sequence, and dry it under vacuum to obtain carborane m-3-py. Alternatively, a solution of n-butyllithium in n-hexane can be slowly added dropwise to a solution of meta-carborane in diethyl ether. After the addition is complete, the mixture is stirred at -90 to -70°C for 0.5 to 2 hours. Then, phenyl isothiocyanate is added at room temperature, and the mixture is stirred at room temperature for another 20 to 36 hours. After the reaction is complete, dilute hydrochloric acid is added to quench the reaction, the organic phase is separated, the aqueous phase is extracted with diethyl ether, the organic phases are combined, evaporated to dryness by rotary evaporation, and then purified by silica gel column chromatography to obtain carborane ms-ph. Step 3: Disperse carborane m-3-py or ms-ph and BiSbTe-Pb powder in ethanol at a mass ratio of 0.1 to 0.9:100, stir evenly, and then evaporate to dryness by rotary evaporation to obtain BiSbTe-Pb powder of composite carborane. Step 4: The BiSbTe-Pb powder of composite carborane is subjected to discharge plasma sintering to obtain a bulk BiSbTe-Pb thermoelectric material of composite carborane.

2. The preparation method according to claim 1, characterized in that, In step 1, the molar ratio of bismuth trichloride, antimony trichloride, tellurium powder, and lead acetate trihydrate is 0.4:1.6:3:0.008, the solvothermal reaction temperature is 200℃, and the reaction time is 12h.

3. The preparation method according to claim 1, characterized in that, In step 1, the washing is performed twice with deionized water and twice with anhydrous ethanol. The centrifugation conditions are 10000 r / min for 3 to 5 min, the vacuum drying temperature is 50℃ to 70℃, and the drying time is 10 to 14 h.

4. The preparation method according to claim 1, characterized in that, In step 2, the concentration of the n-butyllithium hexane solution is 1.4–1.7 mol / L, and the concentration of the meta-carborane diethyl ether solution is 0.05–0.15 mol / L.

5. The preparation method according to claim 1, characterized in that, In step 2, the molar ratio of n-butyllithium, meta-carborane, 3-pyridyl isothiocyanate or benzene isothiocyanate is 1:1:1.5 to 3.

6. The preparation method according to claim 1, characterized in that, In step 3, the mass ratio of carborane m-3-py or ms-ph to BiSbTe-Pb powder is 0.1 to 0.7:

100.

7. The preparation method according to claim 1, characterized in that, In step 3, the stirring time is 1 to 2 hours, and the rotary evaporation temperature is 58 to 60°C.

8. The preparation method according to claim 1, characterized in that, In step 4, the sintering temperature of the discharge plasma sintering is 400-500℃, the holding time is 3-7 minutes, and the sintering pressure is 50-70MPa.

9. The preparation method according to claim 1, characterized in that, In step 4, the sintering temperature of the discharge plasma sintering is 420℃, the holding time is 5min, and the sintering pressure is 60MPa.

10. A BiSbTe-Pb thermoelectric material composed of composite carborane prepared by any one of the preparation methods according to claims 1 to 9.

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