阅读说明：本技术 一种通过引入稳定的纳米异质结提高p型SnTe基材料热电性能的方法 (Method for improving thermoelectric performance of p-type SnTe base material by introducing stable nano heterojunction ) 是由 张久兴 张静文 李松 吴镇旺 杨新宇 于 2020-12-24 设计创作，主要内容包括：本发明公开了一种通过引入稳定的纳米异质结提高p型SnTe基材料热电性能的方法,是通过在p型SnTe基材料中引入n型的碳包覆PbTe纳米颗粒,构建为纳米异质结,从而提高p型SnTe基材料的热电性能。本发明的工艺简单、操作方便、可重复性高。(The invention discloses a method for improving thermoelectric property of a p-type SnTe base material by introducing a stable nano heterojunction. The method has the advantages of simple process, convenient operation and high repeatability.)

1. A method for improving thermoelectric performance of a p-type SnTe base material by introducing a stable nano heterojunction is characterized by comprising the following steps: n-type carbon-coated PbTe nano particles are introduced into the p-type SnTe base material to construct a nano heterojunction, so that the thermoelectric property of the p-type SnTe base material is improved.

2. The method of claim 1, comprising the steps of:

step 1, preparing Sn by vacuum tube-sealing smelting method_1-xM_xTe alloy powder

Weighing Sn, Te and M particles with the purity of not less than 99.99 percent according to the stoichiometric ratio, placing the Sn, Te and M particles into a quartz tube, and sealing the quartz tube; then placing the sealed quartz tube in a muffle furnace, heating to 1000-1200 ℃ at a heating rate of 5-30 ℃/min, and preserving heat for 4-24 hours to enable the raw materials to be completely alloyed in a molten state to obtain Sn_1-xM_xTe alloy powder;

step 2, preparing PbTe nano particles by hydrothermal method

Weighing a proper amount of NaOH, dissolving the NaOH in deionized water, placing the solution on a magnetic stirrer for continuous stirring, and sequentially and slowly adding raw material NaBH in the stirring process₄、Pb(CH₃COO)₂·3H₂O and TeO₂Continuously stirring uniformly to obtain a clear mixed solution; transferring the obtained mixed solution into a reaction kettle, and placing the reaction kettle in a forced air drying oven for heat preservation at 150-180 ℃ for 24-36 h; after the reaction kettle is cooled to room temperature, repeatedly cleaning and centrifuging the mixed solution in the reaction kettle, then soaking the centrifugate in dilute nitric acid for 30-60 min, and finally placing the reaction product in a vacuum drying oven for heat preservation at 60-70 ℃ for 20-24 h to obtain PbTe nano-particles;

step 3, coating treatment of the surface of PbTe nano particles

Dispersing the PbTe nano particles prepared in the step 2 in deionized water, placing the mixture on a magnetic stirrer for continuous stirring, and simultaneously adding dopamine hydrochloride; stirring for 30-90 min, and adding a buffer triaminomethane solution of 20mmol/L into the obtained mixed solution; after reacting for 3-6 h, repeatedly centrifuging and cleaning the reactant by using deionized water and absolute ethyl alcohol to obtain PbTe nano particles with the surfaces coated with polydopamine, namely PbTe @ PDA;

step 4, Sn_1-xM_xPreparation of Te-y% PbTe @ C powder

According to (100-y)%: y% of Sn_1-xM_xMixing and stirring Te alloy powder and PbTe @ PDA in ethanol at normal temperature for 4-24 h, then placing the solution in a vacuum drying oven, and drying at 50-70 ℃ for 48-72 h; then the mixed powder is put into a tube furnace and annealed for 3 hours at 300 ℃ in a hydrogen-argon mixed atmosphere to obtain the Sn carbonized by the coating layer_1-xM_xTe-y% PbTe @ C powder;

step 5, Sn_1-xM_xSintering of Te-y% PbTe @ C powder

Sn obtained in the step 4_1-xM_xAnd (3) placing the Te-y% PbTe @ C powder into a graphite die for spark plasma sintering, and obtaining a target product after sintering.

3. The method of claim 1, wherein: in the step 1, M is at least one of Sb, Bi, Mg, Mn, In, Cd, Hg and Ge, and x is 0-0.10.

4. The method of claim 1, wherein: in the step 1, a quartz tube is sealed by using an oxyhydrogen generator, and is pre-vacuumized by using a mechanical pump and then vacuumized to 10 ℃ by using a molecular pump^-5Torr and sealing the tube.

5. The method of claim 1, wherein: in step 2, NaOH, deionized water and NaBH₄、Pb(CH₃COO)₂·3H₂O and TeO₂The dosage ratio of the components is 1.2 g: 30mL of: 0.9 g: 3 mmol: 3 mmol.

6. The method of claim 1, wherein: in step 3, the dosage ratio of the PbTe nano particles, deionized water, dopamine hydrochloride and buffer triaminomethane solution is 0.3 g: 200mL of: 0.3 g: 200 mL.

7. The method of claim 1, wherein: in step 4, y is 1-15.

8. The method of claim 1, wherein: in step 4, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere used for annealing was 5%.

9. The method of claim 1, wherein: in step 4, the sintering temperature of the spark plasma sintering is 550 ℃, the heat preservation time is 5min, and the heating rate is 50 ℃/min.

Technical Field

The invention relates to a method for improving thermoelectric performance of a p-type SnTe base material by introducing a stable nano heterojunction, belonging to the field of thermoelectric materials.

Background

The performance of thermoelectric materials is closely related to a dimensionless thermoelectric figure of merit ZT, which is defined by the formula ZT ═ S²σ/k_tot＝S²σ/(k_ph+k_el) Where S is the seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, k_totIs made by electronic heat conduction (k)_el) And lattice thermal conductance (k)_ph) The total thermal conductivity of the composition. In recent decades, thermoelectric technology has been used in many industries, typically for the recovery of waste heat from automobilesThe field of industry is becoming more and more widespread. The temperature range of waste heat generated in actual industrial production is about 500-900K, so that the development of the thermoelectric material in the middle temperature region (400-900K) is important for realizing the sustainable development of energy. To date, medium-temperature region p-type thermoelectric materials with excellent performance mainly include PbX and SnX (X ═ Te, Se, S). Among them, various researchers found that SnTe has the same crystal structure and energy band structure as PbTe and PbSe and is non-toxic, and thus is considered to have a potential to replace PbTe. However, since SnTe has more intrinsic Sn vacancies, it is expressed as heavy hole doping (10)²⁰～10²¹cm^-3) The P-type semiconductor of (2) thus has a lower seebeck coefficient and a higher electron thermal conductivity. Meanwhile, the simple crystal structure SnTe has higher lattice thermal conductivity (about 3W/mK) at room temperature, so that the ZT value of pure SnTe is only 0.4.

Currently, an n-type second phase (such as InSb, TiN, YbO) is artificially introduced into p-type SnTe₃Etc.) is considered to be an effective method for reducing the thermal conductivity of the crystal lattice. In fact, in the processes of spark plasma sintering and hot-pressing sintering, due to the problems of large specific surface area, high surface activity and the like, nano particles can rapidly grow from a few nanometers and dozens of nanometers to hundreds of nanometers or even microns, and therefore the nano effect is weakened. While PbTe of the intermediate-temperature-region thermoelectric material also exhibits a significant n-type semiconductor characteristic above 270 ℃. Therefore, stable n-type PbTe nano particles are selected to be compounded with p-type SnTe micro particles, so that the concentration of the carrier of the matrix can be regulated and controlled, the Seebeck coefficient can be improved, the electronic thermal conductivity can be reduced, and the formed multi-scale phonon scattering center can be more favorable for reducing the lattice thermal conductivity, thereby influencing the thermoelectric property of the material.

Disclosure of Invention

Based on the defects of the prior art, the invention aims to provide a method for improving the thermoelectric performance of a p-type SnTe-based material by introducing a stable nano heterojunction.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for improving thermoelectric performance of a p-type SnTe base material by introducing a stable nano heterojunction is characterized by comprising the following steps: the n-type carbon-coated PbTe nano particles are introduced into the p-type SnTe base material to construct a stable nano heterojunction, so that the carrier concentration can be regulated, the Seebeck coefficient is improved, the electron thermal conductivity is reduced, the appearance and the size of PbTe nano crystals can be maintained in the sintering process, more phonon scattering centers are introduced, the lattice thermal conductivity is reduced, and the effect of improving the thermoelectric property of the p-type SnTe base material is finally achieved. The method specifically comprises the following steps:

step 1, preparing Sn by vacuum tube-sealing smelting method_1-xM_xTe alloy powder

Weighing Sn, Te and M particles with the purity of not less than 99.99 percent according to the stoichiometric ratio, placing the Sn, Te and M particles into a quartz tube, and sealing the quartz tube; then placing the sealed quartz tube in a muffle furnace, heating to 1000-1200 ℃ at a heating rate of 5-30 ℃/min, and preserving heat for 4-24 hours to enable the raw materials to be completely alloyed in a molten state to obtain Sn_1-xM_xTe alloy powder;

step 2, preparing PbTe nano particles by hydrothermal method

Weighing a proper amount of NaOH, dissolving the NaOH in deionized water, placing the solution on a magnetic stirrer for continuous stirring, and sequentially and slowly adding raw material NaBH in the stirring process₄、Pb(CH₃COO)₂·3H₂O and TeO₂Continuously stirring uniformly to obtain a clear mixed solution; transferring the obtained mixed solution into a reaction kettle, and placing the reaction kettle in a forced air drying oven for heat preservation at 150-180 ℃ for 24-36 h; after the reaction kettle is cooled to room temperature, repeatedly cleaning and centrifuging the mixed solution in the reaction kettle, then soaking the centrifugate in dilute nitric acid for 30-60 min, and finally placing the reaction product in a vacuum drying oven for heat preservation at 60-70 ℃ for 20-24 h to obtain PbTe nano-particles;

step 3, coating treatment of the surface of PbTe nano particles

Dispersing the PbTe nano particles prepared in the step 2 in deionized water, placing the mixture on a magnetic stirrer for continuous stirring, and simultaneously adding dopamine hydrochloride; stirring for 30-90 min, and adding a buffer triaminomethane solution of 20mmol/L into the obtained mixed solution; after reacting for 3-6 h, repeatedly centrifuging and cleaning the reactant by using deionized water and absolute ethyl alcohol to obtain PbTe nano particles with the surfaces coated with polydopamine, namely PbTe @ PDA;

step 4, Sn_1-xM_xPreparation of Te-y% PbTe @ C powder

According to (100-y)%: y% of Sn_1-xM_xMixing and stirring Te alloy powder and PbTe @ PDA in ethanol at normal temperature for 4-24 h, then placing the solution in a vacuum drying oven, and drying at 50-70 ℃ for 48-72 h; then placing the mixed powder into a tube furnace, and annealing for 3 hours at 300 ℃ in a hydrogen-argon mixed atmosphere to obtain the Sn carbonized by the coating layer_1-xM_xTe-y% PbTe @ C powder;

step 5, Sn_1-xM_xSintering of Te-y% PbTe @ C powder

Sn obtained in the step 4_1-xM_xAnd (3) placing the Te-y% PbTe @ C powder into a graphite die for spark plasma sintering, and obtaining a target product after sintering.

Preferably, In step 1, M is at least one of Sb, Bi, Mg, Mn, In, Cd, Hg and Ge, and x is 0 to 0.10.

Preferably, in step 1, the quartz tube is sealed by using an oxyhydrogen generator, and the quartz tube is pre-vacuumized by using a mechanical pump and then vacuumized to 10 ℃ by using a molecular pump^-5Torr and sealing the tube.

Preferably, in step 2, NaOH, deionized water and NaBH₄、Pb(CH₃COO)₂·3H₂O and TeO₂The dosage ratio of the components is 1.2 g: 30mL of: 0.9 g: 3 mmol: 3 mmol.

Preferably, in step 3, the ratio of the PbTe nanoparticles, deionized water, dopamine hydrochloride, and buffer triaminomethane solution is 0.3 g: 200mL of: 0.3 g: 200 mL.

Preferably, in the step 4, y is 1-15.

Preferably, in step 4, the volume fraction of hydrogen in the hydrogen-argon mixed atmosphere used for annealing is 5%.

Preferably, in step 4, the sintering temperature of the spark plasma sintering is 550 ℃, the holding time is 5min, and the heating rate is 50 ℃/min.

Compared with the prior art, the invention has the beneficial effects that:

1. according to the invention, by introducing n-type carbon-coated PbTe nano particles, a stable nano heterojunction is constructed in the p-type SnTe-based thermoelectric material, so that the Seebeck coefficient is favorably improved, the electronic thermal conductivity and the lattice thermal conductivity are favorably reduced, and the effect of obviously improving the SnTe thermoelectric property is finally achieved.

2. The PbTe nano-particles prepared by the invention have the advantages of uniform size (50-120 nm), high purity and controllable morphology, and the thickness of the C layer coated on the surface of the PbTe nano-particles is uniform (about 5nm), and the PbTe nano-particles are stable and difficult to peel off, thereby effectively avoiding the problem of rapid growth of crystal grains in the traditional sintering process.

3. The method has the advantages of simple process, convenient operation, high repeatability, complete obtained sample and stable performance after repeated tests.

4. The method has universality and can be widely applied to other thermoelectric material systems.

Drawings

FIG. 1 is an XRD pattern of a sample prepared in each example, in which (A) curve corresponds to Sn prepared in step 1 in example_0.95Sb_0.05Te powders, (B), (C) and (D) curves correspond to Sn prepared in example 1, example 2 and example 3, respectively_0.95Sb_0.05Te-5％[email protected]、Sn_0.95Sb_0.05Te-2.5% PbTe @ C and Sn_0.95Sb_0.05Te-7.5% PbTe @ C sample.

Fig. 2 is an SEM image of PbTe nanoparticles surface-coated with polydopamine prepared in step 3 in each example, wherein fig. 2(a) and fig. 2(B) are at different magnifications.

FIG. 3 shows Sn prepared in example 1_0.95Sb_0.05Fracture morphology plot of the Te-5% PbTe @ C sample, wherein FIG. 3(B) is a partial magnified view of FIG. 3 (A).

FIG. 4 shows Sn prepared in example 1_0.95Sb_0.05Comparative graph of three repeated thermoelectric performance tests (test temperature 600 ℃) for samples of Te-5% PbTe @ C (test temperature), in which FIG. 4(A) and FIG. 4(B) are Seebeck coefficient and resistance, respectivelyThe ratio is compared with the graph.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below. The following disclosure is merely exemplary and illustrative of the inventive concept, and those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Example 1

The method for improving the thermoelectric performance of the p-type SnTe-based material by introducing the stable nano heterojunction comprises the following steps:

step 1, preparing Sn by vacuum tube-sealing smelting method_0.95Sb_0.05Te alloy powder

Weighing Sn, Te and Sb particles with the purity of 99.99 percent according to the stoichiometric ratio, placing the Sn, Te and Sb particles into a dry and clean quartz tube with the outer diameter of 25mm, sealing the quartz tube by using an oxyhydrogen generator, pre-vacuumizing by using a mechanical pump, and vacuumizing to 10 ℃ by using a molecular pump^-5Torr and sealing the tube; then the sealed quartz tube is placed in a muffle furnace, the temperature is raised to 1000 ℃ at the heating rate of 15 ℃/min, and the temperature is kept for 4h, so that the raw materials are completely alloyed in a molten state, and Sn is obtained_0.95Sb_0.05And (3) Te alloy powder.

Step 2, preparing PbTe nano particles by hydrothermal method

Weighing 1.2g of NaOH and dissolving in 30mL of deionized water, placing the solution on a magnetic stirrer for continuous stirring, and sequentially and slowly adding 0.9g of NaBH in the stirring process₄3mmol of Pb (CH)₃COO)₂·3H₂O and 3mmol of TeO₂Continuously stirring uniformly to obtain a clear mixed solution; transferring the obtained mixed solution into a reaction kettle, and placing the reaction kettle in a forced air drying oven for heat preservation at 160 ℃ for 24 hours; after the reaction kettle is cooled to room temperature, repeatedly cleaning and centrifuging the mixed solution in the reaction kettle, then soaking the centrifugate for 30min by using dilute nitric acid with the concentration of 6mol/L, and finally, carrying out centrifugal separation on the mixed solutionPlacing the reaction product in a vacuum drying oven, and keeping the temperature at 60 ℃ for 24h to obtain PbTe nano-particles;

step 3, coating treatment of the surface of PbTe nano particles

Dispersing 0.3g of PbTe nano particles prepared in the step 2 in 200mL of deionized water, placing the solution on a magnetic stirrer, continuously stirring the solution, and simultaneously adding 0.3g of dopamine hydrochloride; stirring for 30min, and adding 200mL of 20mmol/L buffer triaminomethane solution into the obtained mixed solution; after reacting for 4h, repeatedly centrifuging and cleaning the reactant by using deionized water and absolute ethyl alcohol to obtain the PbTe nano-particles with the surface coated with polydopamine, namely PbTe @ PDA.

Step 4, Sn_0.95Sb_0.05Preparation of Te-5% PbTe @ C powder

According to the ratio of 95%: 5% by mass of Sn_0.95Sb_0.05The Te alloy powder and PbTe @ PDA were mixed and stirred in ethanol at normal temperature for 4 hours, and then the solution was placed in a vacuum drying oven and dried at 65 ℃ for 48 hours. Then the mixed powder is put into a tube furnace and annealed for 3 hours at 300 ℃ in a hydrogen-argon mixed atmosphere with the volume fraction of hydrogen of 5 percent, and the Sn carbonized by the coating layer is obtained_0.95Sb_0.05Te-5% PbTe @ C powder.

Step 5, Sn_0.95Sb_0.05Sintering of Te-5% PbTe @ C powder

Putting the powder obtained in the step 4 into a graphite die with the diameter of 20mm for spark plasma sintering to obtain Sn_0.95Sb_0.05Te-5% PbTe @ C sample, the sintering temperature is 550 ℃, the heat preservation time is 5min, and the heating rate is 50 ℃/min.

Example 2

This example is a method of improving thermoelectric performance of p-type SnTe based material by introducing stable nano-heterojunction according to the same method as example 1, and the difference is only: in step 4, Sn_0.95Sb_0.05The mass ratio of the Te alloy powder to the PbTe @ PDA powder is 97.5%: 2.5%, the sample obtained is denoted Sn_0.95Sb_0.05Te-2.5％[email protected]。

Example 3

This example was carried out in the same manner as in example 1,the method for improving the thermoelectric performance of the p-type SnTe base material by introducing the stable nano heterojunction only has the following differences: in step 4, Sn_0.95Sb_0.05The mass ratio of the Te alloy powder to the PbTe @ PDA powder is 92.5%: 7.5%, the sample obtained is denoted Sn_0.95Sb_0.05Te-7.5％[email protected]。

FIG. 1 is an XRD pattern of a sample prepared in the above example, in which (A) curve corresponds to Sn prepared in step 1 of the example_0.95Sb_0.05Te powders, (B), (C) and (D) curves correspond to Sn prepared in example 1, example 2 and example 3, respectively_0.95Sb_0.05Te-5％[email protected]、Sn_0.95Sb_0.05Te-2.5% PbTe @ C and Sb_0.05Te-7.5% PbTe @ C bulk sample, it can be seen that only two phases of SnTe and PbTe are present in the sample.

Fig. 2 is an SEM image of PbTe nanoparticles surface-coated with polydopamine prepared in step 3 of the above example, wherein fig. 2(a) and 2(B) are at different magnifications. It is obvious that polydopamine with a thickness of about 5nm is successfully coated on the surface of the PbTe nano-particles, and meanwhile, the PbTe nano-particles are cubic, have uniform grain sizes and have grain diameters of about 60-150 nm.

FIG. 3 shows Sn prepared in example 1_0.95Sb_0.05Fracture morphology plot of the Te-5% PbTe @ C sample, wherein FIG. 3(B) is a partial magnified view of FIG. 3 (A). As can be seen from fig. 3(a), the fractures are composed of micro-scale and nano-scale grains and are uniformly distributed. As is apparent from fig. 3(B), the PbTe nanocrystals coated with the carbon layer still maintain the morphology and grain size during chemical synthesis after spark plasma sintering, indicating that the coating layer indeed inhibits the grain growth.

FIG. 4 shows Sn prepared in example 1_0.95Sb_0.05Comparative graph of Te-5% PbTe @ C samples from three repeated thermoelectric performance tests (test temperature 600 ℃). It can be clearly seen that the samples prepared by the invention have stable performance after being tested for many times, which also indicates that the coating layer is very stable and can not be damaged by repeated tests, and can still play a role in inhibiting the growth of nano-crystalline grains.

Table 1 shows the test temperatures at 600 deg.CThermoelectric properties of the articles were compared and the data indicated: sn prepared in example 1 compared to SnTe_0.95Sb_0.05The Seebeck coefficient (Seeback coefficient) of the Te-5% PbTe @ C sample is improved by about 37.7%, the thermal conductivity is reduced by 50%, the ZT value is improved by about 127.3%, and the thermoelectric property is greatly improved.

TABLE 1

The present invention is not limited to the above exemplary embodiments, and any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.