P-type SnTe-based thermoelectric material and preparation method thereof

Abstract

The application discloses a P-type SnTe-based thermoelectric material and a preparation method thereof. 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe, wherein 0 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe material is up to 1.35 at 843 K. The high thermoelectric figure of merit can greatly improve the conversion efficiency of the thermoelectric material in waste heat power generation and thermoelectric refrigeration. Meanwhile, the preparation method of the thermoelectric material has the advantages of simple process, easy scale production and strong practicability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of energy materials, and particularly relates to a P-type tin telluride-based thermoelectric material and a preparation method. BACKGROUND

[0002] Thermoelectric materials can directly convert heat energy into electricity without moving parts and working medium, and do not emit any toxic and harmful substances, and belong to typical green energy materials. Devices made of thermoelectric materials can be used for waste heat recovery and static refrigeration, for example, it can use the large amount of waste heat discharged by power plants and boilers to generate electricity, can use solar heat to generate electricity, and can directly use geothermal energy to generate electricity. The development of this almost inexhaustible energy will fundamentally alleviate the energy shortage situation people are facing once the efficiency problem is solved. In addition, as a refrigerator thermoelectric device, it can be used for cooling of laser diodes, infrared detectors and computer CPUs.

[0003] Lead telluride is currently the most superior medium-high temperature thermoelectric material, which has been successfully applied to power supply of deep space probes, but the toxicity of lead limits its wide application. Nontoxic and environmentally friendly tin telluride has the same crystal structure and similar double valence band energy band structure as lead telluride, and is a very potential thermoelectric material. However, the energy difference between the valence bands of the original sample of tin telluride is large, the hole concentration is too high, and the thermal conductivity is high, which leads to a very low thermoelectric figure of merit of tin telluride, which is not conducive to the mutual conversion between heat and electricity. At present, a large number of research works try to reduce the hole concentration by N-type doping to improve the thermoelectric figure of merit of the material. However, the current doping strategies have little effect on reducing the energy difference between the double valence bands of tin telluride, so that the improvement of the thermoelectric figure of merit of the material is very limited. Therefore, it is an urgent problem to be solved to find a doping alloying regulation strategy to realize the convergence of the valence bands of tin telluride and significantly improve its thermoelectric figure of merit. SUMMARY

[0004] To solve the above problems, the application provides a P-type tin telluride thermoelectric material and a preparation method. 0.79 Sb 0.06 Ge 0.15 The thermoelectric figure of merit of the Te-4% CdTe thermoelectric material reaches 1.35 at 843K. At the same time, the preparation method of the thermoelectric material has the advantages of simple process, easy to scale production and strong practicability.

[0005] The application adopts the following technical scheme:

[0006] In a first aspect, the present application provides a P-type SnTe-based thermoelectric material, which is used for thermoelectric power generation or thermoelectric refrigeration, and has a chemical formula of Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe, wherein Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe, wherein Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe, wherein Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe, wherein 0

[0007] Preferably, the P-type SnTe-based thermoelectric material has a chemical formula of Sn 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe.

[0008] In a second aspect, the present application provides a method for preparing a P-type SnTe-based thermoelectric material, which specifically comprises the following steps:

[0009] S1, preparing raw materials Sn particles, Sb particles, Ge particles, Cd particles and Te particles;

[0010] S2, weighing the elements Sn, Sb, Ge, Cd and Te according to the atomic ratio, and pouring them into a dried quartz tube, sealing the quartz tube after vacuumizing, and obtaining a Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe compound.

[0011] S3, grinding the ingot obtained in S2, and then sintering to obtain the thermoelectric material.

[0012] Preferably, the purity of the elements Sn, Sb, Ge, Cd and Te in step S1 is greater than 99%.

[0013] Preferably, in step S2, the specific process of vacuum melting reaction is as follows: heating from room temperature to 1000℃, 1050℃, 1100℃ or 1150℃ at a heating rate of 40℃ / h, 50℃ / h, 60℃ / h, 70℃ / h or 80℃ / h, and keeping the temperature for 5h, 5.5h, 6h, 6.5h, 7h, 7.5h or 8h, and then water quenching to obtain a Sn 0.79 Sb 0.06 Ge0.15 Te-x%CdTe compound; preferably the specific process of the reaction is: temperature is raised to 1050℃ for 16 hours, temperature is kept at 1050℃ for 6h, water quenching, to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe compound;

[0014] Preferably, in step S3, sintering adopts discharge plasma spark sintering or hot-pressing sintering, the rate of temperature rise to the sintering temperature is 5℃ / min, 10℃ / min, 20℃ / min, 30℃ / min, 40℃ / min, 50℃ / min, 60℃ / min, 70℃ / min, 80℃ / min, 90℃ / min, 100℃ / min, 110℃ / min, 120℃ / min, 130℃ / min, 140℃ / min or 150℃ / min; the sintering temperature is 400℃, 420℃, 440℃, 460℃, 480℃, 500℃, 520℃, 540℃, 560℃, 580℃ or 600℃; the sintering pressure is 10Mpa, 20Mpa, 30Mpa, 40Mpa, 50Mpa, 70Mpa, 100Mpa, 200Mpa or 250Mpa; the sintering time is 5min, 10min, 20min, 40min, 60min, 80min, 100min or 120min. Preferably, in the process of discharge plasma spark sintering, the temperature is raised from room temperature to 500℃ for 7min, and sintering is carried out at 500℃ and 40MPa for 10min.

[0015] The above technical solution has the following advantages:

[0016] The experiment uses non-toxic and environmentally friendly tin and tellurium elements as raw materials, which solves the problem of lead toxicity in traditional lead telluride-based thermoelectric materials from the source, and the prepared P-type tin telluride thermoelectric material has high thermoelectric figure of merit, which is conducive to obtaining high thermoelectric conversion efficiency. At the same time, the preparation method of the thermoelectric material has the advantages of simple process, easy to scale production and strong practicability. The prepared Sn 0.79 Sb 0.06 Ge 0.15 The highest thermoelectric figure of merit of the Te-4%CdTe material is as high as 1.35 at 843K. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The powder X-ray diffraction pattern of the Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe material in Examples 1-3 of the present application;

[0018] Figure 2 Sn for Examples 1-3 of the present invention 0.79 Sb 0.06 Ge 0.15 Temperature dependence of the electrical conductivity of Te-x% CdTe materials;

[0019] Figure 3 Sn for Examples 1-3 of the present invention 0.79 Sb 0.06 Ge 0.15 Temperature dependence of the thermoelectric power of Te-x% CdTe materials;

[0020] Figure 4 Sn for Examples 1-3 of the present invention 0.79 Sb 0.06 Ge 0.15 Temperature dependence of the thermal conductivity of Te-x% CdTe materials;

[0021] Figure 5 Sn for Examples 1-3 of the present invention 0.79 Sb 0.06 Ge 0.15 Temperature dependence of the thermoelectric figure of merit of Te-x% CdTe materials. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the present application more clear, the present application is further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application. Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0023] Prepare raw materials Sn particles, Sb particles, Ge particles, Cd particles and Te particles. Among them, the purity of Sn particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of Sb particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), the purity of Ge particles is 99.999% (produced by Hebei Luohong Technology Co., Ltd.), the purity of Cd particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.), and the purity of Te particles is 99.99% (produced by Hebei Luohong Technology Co., Ltd.).

[0024] Example 1 Sn 0.79 Sb 0.06 Ge 0.15 Preparation of Te-3% CdTe

[0025] 1), according to the atomic ratio, respectively, take the elements Sn, Sb, Ge, Cd and Te, and pour into the dried quartz tube, vacuum sealed quartz tube with hydrogen oxygen flame;

[0026] 2) Put the sealed vacuum quartz tube in step 1) into a muffle furnace for solid phase reaction, the reaction condition is that the temperature is uniformly increased from room temperature to 1050 DEG C for 16 hours, and the temperature is kept at 1050 DEG C for 6 hours, and then water quenching is performed to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-2%CdTe ingot;

[0027] 3) The ingot obtained in step 2) is manually ground for 30 minutes, and then discharge plasma spark sintering is performed at 550 DEG C, 200 MPa and vacuum for 5 minutes to obtain the thermoelectric material.

[0028] Example 2 Sn 0.79 Sb 0.06 Ge 0.15 Preparation of Te-4%CdTe

[0029] 1) Single elements Sn, Sb, Ge, Cd and Te are weighed according to the atomic ratio, and are poured into a dried quartz tube, and the quartz tube is sealed after vacuumizing by using oxyhydrogen flame;

[0030] 2) Put the sealed vacuum quartz tube in step 1) into a muffle furnace for solid phase reaction, the reaction condition is that the temperature is uniformly increased from room temperature to 1050 DEG C for 16 hours, and the temperature is kept at 1050 DEG C for 6 hours, and then water quenching is performed to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe ingot;

[0031] 3) The ingot obtained in step 2) is manually ground for 30 minutes, and then discharge plasma spark sintering is performed at 550 DEG C, 200 MPa and vacuum for 5 minutes to obtain the thermoelectric material.

[0032] Example 3 Sn 0.79 Sb 0.06 Ge 0.15 Preparation of Te-6%CdTe

[0033] 1) Single elements Sn, Sb, Ge, Cd and Te are weighed according to the atomic ratio, and are poured into a dried quartz tube, and the quartz tube is sealed after vacuumizing by using oxyhydrogen flame;

[0034] 2) Put the sealed vacuum quartz tube in step 1) into a muffle furnace for solid phase reaction, the reaction condition is that the temperature is uniformly increased from room temperature to 1050 DEG C for 16 hours, and the temperature is kept at 1050 DEG C for 6 hours, and then water quenching is performed to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-6%CdTe ingot;

[0035] 3) The ingot obtained in step 2) was manually ground for 30 min, and then sintered by spark plasma sintering at 550 °C, 200 MPa and vacuum for 5 min to obtain the thermoelectric material.

[0036] Performance test:

[0037] 1) First, 0.5 g of Sn 0.79 Sb 0.06 Ge 0.15 Te-x% CdTe compound (prepared in Examples 1-3) was weighed, and then the compound was ground into a powder sample using a corundum mortar for powder X-ray diffraction analysis. As shown in FIGS. 1-3, the test angle was 10-90 degrees, and the X-ray diffraction peaks of the prepared sample were completely consistent with the tin telluride standard card, and no existence of impurities was observed. Figure 1 Figure 1 The absence of CdTe diffraction peaks in the attached figures indicates that CdTe forms a solid solution with Sn 0.79 Sb 0.06 Ge 0.15 Te.

[0038] 2) The electrical properties of the materials prepared in Examples 1-3 were tested using a thermoelectric material test system ZEM-3 of Japan Advance Riko Co. The relationship between the electrical conductivity and the thermoelectric potential coefficient with temperature change is shown in FIGS. 4-6. Figure 2 Figure 3 The electrical conductivity of the prepared material decreases with the increase of temperature. The electrical conductivity decreases with the increase of CdTe content. At 874 K, the electrical conductivity of Sn 0.79 Sb 0.06 Ge 0.15 Te-3% CdTe, Sn 0.79 Sb 0.06 Ge 0.15 Te-4% CdTe and Sn 0.79 Sb 0.06 Ge 0.15 Te-6% CdTe is 838 S cm -1 , 739 S cm -1 and 712 S cm -1 , respectively. The absolute value of the thermoelectric potential of the prepared material increases with the increase of temperature. At 874 K, the absolute value of the thermoelectric potential of Sn 0.79 Sb 0.06 Ge 0.15 Te-3% CdTe, Sn 0.79 Sb 0.06 Ge 0.15 Te-4% CdTe and Sn 0.79 Sb 0.06 Ge 0.15 ​​The thermoelectric potentials of Te-6%CdTe are 172 μV K. -1 184μV K -1 and 188 μV K -1 .

[0039] 3) The thermal diffusivity D of the materials prepared in Examples 1-3 was tested using a Netzsch LFA 467 laser flare thermal conductivity meter. Thermal conductivity was determined by κ = C. p Dρ is calculated, density ρ is obtained by Archimedes' method, and specific heat C is obtained by calculation. p Calculated using the Dulong-Petty formula. The relationship between thermal conductivity and temperature is shown in the attached figure. Figure 4 As shown, the thermal conductivity of the prepared material first decreases and then increases with increasing temperature. At 874 K, Sn 0.79 Sb 0.06 Ge 0.15 Te-3%CdTe, Sn 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe and Sn 0.79 Sb 0.06 Ge 0.15 The thermal conductivity of Te-6%CdTe is 1.78 W / m. -1 K -1 1.62 W m -1 K -1 and 1.67 W m -1 K -1 . Figure 5 Sn in Embodiments 1-3 of the present invention 0.79 Sb 0.06 Ge 0.15 The thermoelectric figure of merit of Te-3%CdTe material as a function of temperature is shown in the attached figure. Figure 5 As shown, at 874K, Sn 0.79 Sb 0.06 Ge 0.15 Te-3%CdTe, Sn 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe and Sn 0.79 Sb 0.06 Ge 0.15 The thermoelectric figures of merit for Te-6%CdTe are 1.22, 1.35 and 1.31, respectively.

[0040] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any changes or replacements within the technical scope disclosed by the present application, which can be easily thought by those skilled in the art, should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A P-type SnTe-based thermoelectric material, characterized by: The P-type SnTe-based thermoelectric material has a chemical formula of Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe; wherein, 0 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe indicates that x% of CdTe is solid-solved in Sn 0.79 Sb 0.06 Ge 0.15 Te; wherein, 0 0.79 Sb 0.06 Ge 0.15 Te; wherein, 0 2. A P-type SnTe-based thermoelectric material as claimed in claim 1, characterized by: 3≤x≤6。 3. A P-type SnTe-based thermoelectric material as claimed in claim 1, characterized by: The P-type SnTe-based thermoelectric material is Sn 0.79 Sb 0.06 Ge 0.15 Te-3%CdTe, Sn 0.79 Sb 0.06 Ge 0.15 Te-4%CdTe or Sn 0.79 Sb 0.06 Ge 0.15 Te-6%CdTe.

4. A method of producing a P-type SnTe-based thermoelectric material according to any one of claims 1 to 3, characterized by, Specifically comprising the following steps: S1, preparing raw materials Sn particles, Sb particles, Ge particles, Cd particles and Te particles; S2, Sn, Sb, Ge, Cd and Te are weighed according to the atomic ratio, poured into a quartz tube after drying, sealed after vacuumizing by hydrogen oxygen flame, and then vacuum melted to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe ingot S3, grinding the ingot obtained in step S2, and further performing discharge plasma sintering or hot-pressing sintering to obtain the thermoelectric material.

5. The production method according to claim 4, characterized by: In step S2, the specific process of vacuum melting reaction is as follows: 10-18 hours for temperature rising from room temperature to 1000-1150℃, and keeping the temperature for 5-8 hours, and then water quenching to obtain Sn 0.79 Sb 0.06 Ge 0.15 Te-x%CdTe compound; the temperature rising rate is 40-80℃ / h.

6. The method of producing a thermoelectric material according to claim 4, wherein In step S3, the sintering is performed by discharge plasma sintering or hot-pressing sintering, the sintering temperature is 400-600 ℃, the sintering time is 5-120 min, and the temperature rising rate is 5-150 ℃ / min.

7. The method of producing a thermoelectric material according to claim 4, wherein In step S3, the sintering temperature is 400-600 ℃, and the sintering pressure is 10-250 MPa.

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