CN111490148A - Preparation method of polycrystalline SnSe-based thermoelectric material - Google Patents

Preparation method of polycrystalline SnSe-based thermoelectric material Download PDF

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CN111490148A
CN111490148A CN201910077113.4A CN201910077113A CN111490148A CN 111490148 A CN111490148 A CN 111490148A CN 201910077113 A CN201910077113 A CN 201910077113A CN 111490148 A CN111490148 A CN 111490148A
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snse
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thermoelectric material
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CN111490148B (en
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张家华
徐静涛
蒋俊
乐松
江浩川
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Ningbo Institute of Material Technology and Engineering of CAS
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    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
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Abstract

The invention provides a preparation method of a polycrystalline SnSe-based thermoelectric material. The method comprises the steps of preparing SnSe-based polycrystalline ingot casting through smelting, adding one or more of Te, Se, Pb, Br, Sn, Sb and Bi as sintering aids in the ingot casting ball milling process to obtain powder, and sintering the powder into a block through hot pressing. The method can promote the recrystallization and the directional rearrangement of the crystal grains, improve the orientation degree of the crystal grains and optimize the texture degree of the SnSe-based thermoelectric material, thereby improving the thermoelectric property of the SnSe-based thermoelectric material and having good application prospect.

Description

Preparation method of polycrystalline SnSe-based thermoelectric material
Technical Field
The invention belongs to the technical field of thermoelectric materials, and relates to a preparation method of a polycrystalline SnSe-based thermoelectric material.
Background
The thermoelectric material directly realizes the mutual conversion of electric energy and heat energy by utilizing the transport energy of phonons and carriers. Over the past several years, Thermoelectric (TE) materials have attracted continuous attention from countries around the world as a new green, energy-saving and environmentally friendly material. The thermoelectric equipment has the advantages of small volume, no noise, no external transmission device, low cost, energy conservation, environmental protection and the like, so that the thermoelectric equipment has related application in the market gradually at present and has wide future prospect.
The performance of thermoelectric materials is defined by a dimensionless thermoelectric figure of merit (ZT value): ZT ═ S2σ T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the temperature. The widespread use of current thermoelectric technology is limited by the low conversion efficiency of thermoelectric materials. Thermoelectric figure of merit is directly related to conversion efficiency, and to achieve high thermoelectric figure of merit, two strategies are possible: 1. high power factor (S)2σ), 2, low thermal conductivity (κ). Wherein S can be effectively improved by means of doping of resonant state energy level, carrier concentration regulation, band gap contraction and the like2A value of σ; and methods to reduce thermal conductance include layered architecture, nano-precipitation, introduction of point defects and dislocations.
In recent years, single crystal SnSe prepared by Bridgman et al using the Bridgman method has been reported to have a ZT value exceeding 2.0 (L. D ZHao. et. science 2016), which is a group of thermoelectric materials having the best performance so far.
For example, doping Ag, Zn, Br, BiCl3, PbBr2 and the like are effective methods in P-type and n-type polycrystalline SnSe, Anxifeng and the like prepare Na-doped polycrystalline SnSe by combining a smelting method and hot-pressing sintering, and the carrier concentration of the Na-doped polycrystalline SnSe reaches about 2.7 × 10 at room temperature19cm-3ZT is 0.8 at 773K (z.ren et al j. mater.chem.a,2015), but at the same time there is a great room for improvement in ZT values. There have also been studies to optimize polycrystals by varying the synthesis methodSnSe texture to improve thermoelectric performance, for example, texture degree of the sample is controlled by control of sintering temperature in SPS process to make average ZT value to 0.38(j.he et al phys. Additionally, jiang jun et al prepared polycrystalline SnSe using the local melting and SPS method, with ZT values over 1.0(j.jiang et al j.mater.chem.a,2016) due to high texture and hole concentration.
Disclosure of Invention
Aiming at the current research situation, the invention provides a preparation method of a polycrystalline SnSe-based thermoelectric material, which is simple and feasible, and can effectively optimize the texture of the polycrystalline SnSe-based thermoelectric material and improve the electrical property of the polycrystalline SnSe-based thermoelectric material, thereby obtaining good thermoelectric property.
The technical scheme of the invention is as follows: a preparation method of a polycrystalline SnSe-based thermoelectric material comprises the following steps:
preparing raw materials according to the stoichiometry of the SnSe-based thermoelectric material;
smelting the raw materials to obtain a SnSe-based polycrystalline ingot;
carrying out ball milling on the SnSe-based polycrystal ingot to obtain powder, and then carrying out hot-pressing sintering to obtain a block material;
the method is characterized in that: adding a sintering aid in the SnSe-based polycrystalline ingot ball milling process to perform mixed ball milling;
the sintering aid is at least one of Te, Se, Pb, Br, Sn, Sb and Bi; and the mass of the sintering aid accounts for 5-50% of that of the SnSe-based polycrystalline ingot.
The chemical structural formula of the SnSe-based thermoelectric material can be MxSn1-xSe, wherein M is at least one of Na, Ag, Pb, Cu, Mn, K, Zn, In, Bi, Sb and the like, and x is more than or equal to 0 and less than or equal to 0.5.
As an implementation mode, the smelting process comprises the following steps: and (3) placing the raw material vacuum sealed tube in a quartz tube, placing the quartz tube in a smelting furnace, heating to smelt the raw material, and naturally cooling the quartz tube to room temperature after smelting is finished to obtain the SnSe-based polycrystalline ingot.
Preferably, the particle size is in the range of 0.5 to 500. mu.m.
Preferably, the raw materials are filled in a quartz tube, and the quartz tube is vacuumized to be less than or equal to 5Pa and then sealed.
Preferably, the smelting furnace is a high-temperature sintering furnace, and the quartz tube swings in the smelting process to uniformly mix the raw materials.
Preferably, the temperature is raised to 850-1000 ℃ in the smelting process.
As one implementation manner, the hot-pressing sintering process is as follows: and putting the powder into a mold, putting the mold into a vacuum hot-pressing furnace, vacuumizing to no more than 10Pa, and carrying out hot pressing. Preferably, the hot-pressing sintering temperature is 350-550 ℃, and the pressure is 50-80 Mpa.
More preferably, the temperature increase rate is controlled to 3 ℃/min to 30 ℃/min.
Further preferably, the pressurizing rate is controlled to be 1MPa/min to 30 MPa/min.
More preferably, the holding time is 10 to 20 min.
Further preferably, the pressure release rate after completion of the sintering is 20 MPa/min.
Compared with the prior art, the invention prepares the SnSe-based polycrystalline ingot by a smelting method, as shown in figure 1, adding one or more of Te, Se, Pb, Br, Sn, Sb and Bi as sintering aids in the ingot ball milling process to obtain powder, carrying out hot-pressing sintering on the powder, the sintering aid is melted into liquid in the hot-pressing sintering process to form a liquid-phase sintering mode, and the liquid sintering aid promotes the recrystallization and directional rearrangement of crystal grains in combination with the pressurizing process, the crystal grains form a certain orientation, the texture degree of the SnSe-based thermoelectric material is optimized, the electric transport performance of the SnSe-based thermoelectric material is closer to that of a single crystal, therefore, the thermoelectric property of the SnSe-based thermoelectric material is improved, on the other hand, a large amount of liquid sintering aid is extruded out of the die after pressurization, a small amount of liquid sintering aid can possibly fill gaps of SnSe grains, and the occurrence of oxidation is also avoided. The method is simple and easy to implement, and is also suitable for other layered thermoelectric materials, the polycrystalline SnSe-based thermoelectric material prepared by the preparation method has high orientation degree and good thermoelectric performance, the crystal orientation degree is greater than or equal to 0.4, the thermoelectric figure of merit at 750-800K is greater than 0.5, and the application prospect is good.
Drawings
FIG. 1 is a schematic view showing the effects of the method for producing a polycrystalline SnSe-based thermoelectric material of the present invention.
FIG. 2 is an XRD spectrum of the polycrystalline SnSe-based thermoelectric material prepared in the embodiments 1-5 of the present invention.
Fig. 3 is a scanning electron microscope photograph of polycrystalline SnSe-based thermoelectric materials prepared in examples 1, 3 and 5 of the present invention.
FIG. 4 shows the Seebeck coefficient of the polycrystalline SnSe-based thermoelectric material prepared in examples 1 to 5 of the present invention as a function of temperature.
FIG. 5 shows the temperature dependence of the electrical conductivity of the polycrystalline SnSe-based thermoelectric materials prepared in examples 1 to 5 of the present invention.
FIG. 6 shows the relationship between the thermal conductivity of the polycrystalline SnSe-based thermoelectric materials prepared in examples 1 to 5 of the present invention and the temperature.
FIG. 7 shows the thermoelectric figure of merit of the polycrystalline SnSe-based thermoelectric materials prepared in examples 1 to 5 of the present invention as a function of temperature.
Fig. 8 is a comparison of the average thermoelectric figure of merit of the polycrystalline SnSe-based thermoelectric material prepared in example 5 of the present invention with that of a conventional polycrystalline SnSe-based thermoelectric material.
Detailed Description
The present invention will be described in further detail with reference to the following examples and drawings, which are intended to facilitate the understanding of the present invention and are not intended to limit the present invention in any way.
Example 1:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Weighing Sn particles, Se particles and Na particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then carrying out heat preservation melting at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the cast ingot obtained in the step (4) into a ball milling tank for ball milling for 5min to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10pa, heating to 480 ℃, pressurizing to 60Mpa, controlling the heating rate at 15 ℃/min and the pressurizing rate at 20Mpa/min, keeping the temperature and the pressure for 10min, and releasing the pressure and demolding at 20 Mpa/min.
Example 2:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Weighing Sn particles, Se particles and Na particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then carrying out heat preservation melting at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 5% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 480 ℃ and pressurizing to 60Mpa, wherein the heating rate is controlled at 15 ℃/min, the pressurizing rate is controlled at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Example 3:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Weighing Sn particles, Se particles and Na particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction container in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 15% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 480 ℃ and pressurizing to 60Mpa, wherein the heating rate is controlled at 15 ℃/min, the pressurizing rate is controlled at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Example 4:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Of SeWeighing Sn particles, Se particles and Na particles in a stoichiometric ratio to serve as reaction raw materials;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction container in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 25% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 480 ℃ and pressurizing to 60Mpa, wherein the heating rate is controlled at 15 ℃/min, the pressurizing rate is controlled at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Example 5:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Weighing Sn particles, Se particles and Na particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction container in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then preserving the heat at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 35% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 480 ℃ and pressurizing to 60Mpa, wherein the heating rate is controlled at 15 ℃/min, the pressurizing rate is controlled at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
The bulk samples obtained in examples 1 to 5 were subjected to XRD (X-ray Diffraction) test and thermoelectric property test, respectively, in the direction perpendicular to the pressure direction.
FIG. 2 is an XRD spectrum of examples 1 to 5, and the XRD spectrum is used to calculate the orientation factor, which increases with the increase of the content of Te added, so that the orientation of the sample is optimized. In example 5, the sample orientation factor can be up to 0.56.
It can be seen from the SEM images of the blocks obtained in examples 1, 3 and 5 that the blocks obtained in examples 2 to 5 have a gradually larger crystal grain size and a gradually strengthened sample orientation compared to example 1, for example, the SEM images of the blocks obtained in examples 1, 3 and 5 shown in fig. 3 have a structure in which, during sintering, Te melting is extruded to form liquid phase sintering, so that the sample orientation is greatly optimized, and as the Te content increases, the crystal grain size increases and the sample orientation is strengthened. In addition, if the liquid Te fills the gaps of the SnSe crystal grains, the generation of oxidation is also avoided.
FIGS. 4 to 7 are graphs showing the thermoelectric properties of the polycrystalline SnSe matrix obtained in examples 1 to 5 as a function of temperature. The conductivity change trend of the polycrystalline SnSe researched by the inventor is closer to that of single crystal SnSe. As is clear from fig. 5, the conductivity of the polycrystalline SnSe-based bulk materials obtained in examples 2, 3, 4 and 5 was improved as compared with that of example 1, and particularly, the conductivity of the polycrystalline SnSe-based bulk materials obtained in examples 3, 4 and 5 was remarkably improvedThe maximum value reaches 167Scm at 353K-1The value of the SnSe is about 4 times higher than that of other polycrystal SnSe in a room temperature area. Further, the polycrystalline SnSe substrates obtained in examples 3, 4 and 5 had a maximum value of 98Scm in terms of conductivity at 827K-1And at this time the maximum value of the power factor thereof was 6.9. mu. Wcm-1K-2. As can be seen from the relationship between the thermal conductivity and the thermoelectric figure of merit of the polycrystalline SnSe-based bulk materials obtained in examples 1 to 5 shown in fig. 6 and 7, the thermoelectric figure of merit of the polycrystalline SnSe-based bulk materials obtained in examples 2 to 5 is greater than 0.5 at 750K to 800K, and the thermoelectric figure of merit of the polycrystalline SnSe-based bulk material obtained in example 2 has the highest ZT value at 826K, which is greater than or equal to 0.8, due to the low thermal conductivity and the higher power factor, which is improved by approximately 60% compared to the bulk material obtained in example 1 under the same temperature condition.
FIG. 8 is a graph comparing the average ZT value of the polycrystalline SnSe matrix obtained in example 5 above, and other reported values. As can be seen from fig. 8, the average thermoelectric figure of merit of the polycrystalline SnSe-based bulk material prepared in example 5 can reach 0.45, which is higher than that of the conventional polycrystalline SnSe-based bulk material.
Example 6:
in this example, polycrystalline Sn0.97Na0.03The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Sn0.97Na0.03Weighing Sn particles, Se particles and Na particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 900 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 900 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Se obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Se accounts for 5% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 350 ℃, pressurizing to 60Mpa, controlling the heating rate at 3 ℃/min and the pressurizing rate at 30Mpa/min, keeping the temperature and the pressure for 20min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750-800K in the direction perpendicular to the pressure direction reaches 0.6.
Example 7:
in this embodiment, the preparation method of the polycrystalline SnSe thermoelectric material is as follows:
(1) weighing Sn particles and Se particles according to the stoichiometric ratio of SnSe as reaction raw materials;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction container in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot obtained in the step (4) and Pb into a ball milling tank for ball milling, wherein the mass of the Pb accounts for 15% of that of the ingot, and the ball milling time is 5min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 400 ℃, pressurizing to 60Mpa, controlling the heating rate at 3 ℃/min and the pressurizing rate at 1Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750-800K in the direction perpendicular to the pressure direction reaches 0.95.
Example 8:
in this example, the polycrystal Sb0.05Ag0.05Sn0.9Se0.8Te0.2The preparation method of the thermoelectric material comprises the following steps:
(1) according to Sb0.05Ag0.05Sn0.9Se0.8Te0.2Weighing Sn particles, Se particles, Ag particles, Sb particles and Te particles as reaction raw materials according to the stoichiometric ratio;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction container in a high-temperature sintering furnace, heating to 920 ℃ at the speed of 15 ℃/min, then preserving the heat at 920 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 15% of that of the ingot, and the ball milling time is 10min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 500 ℃, pressurizing to 60Mpa, controlling the heating rate at 20 ℃/min and the pressurizing rate at 15Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750K-800K in the direction perpendicular to the pressure direction reaches 1.05.
Example 9:
in this example, polycrystalline Ag0.03Sn0.97The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Ag0.03Sn0.97Weighing Sn particles, Se particles and Ag particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 1000 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 1000 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot and Te obtained in the step (4) into a ball milling tank for ball milling, wherein the mass of Te accounts for 50% of that of the ingot, and the ball milling time is 10min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 550 ℃, pressurizing to 60Mpa, controlling the heating rate at 15 ℃/min and the pressurizing rate at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750K-800K in the direction perpendicular to the pressure direction reaches 0.84.
Example 10:
in this example, polycrystalline Pb0.04Sn0.96Se0.7Br0.3The preparation method of the thermoelectric material comprises the following steps:
(1) according to Pb0.04Sn0.96Se0.7Br0.3Weighing Sn particles, Se particles, Pb particles and SnBr according to the stoichiometric ratio2As a reaction raw material;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 950 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 950 ℃ for 30min, and then swinging for 30min at the frequency of 5r/min and the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot obtained in the step (4) and Pb into a ball milling tank for ball milling, wherein the mass of the Pb accounts for 35% of that of the ingot, and the ball milling time is 10min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 450 ℃, pressurizing to 60Mpa, controlling the heating rate at 30 ℃/min and the pressurizing rate at 30Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750K-800K in the direction perpendicular to the pressure direction reaches 1.01.
Example 11:
in this example, the polycrystal Bi0.05Sn0.95The preparation method of the Se thermoelectric material comprises the following steps:
(1) according to Bi0.05Sn0.95Weighing Sn particles, Se particles and Bi particles as reaction raw materials according to the stoichiometric ratio of Se;
(2) putting the reaction raw materials weighed in the step (1) into a clean and dry reaction container, vacuumizing the reaction container to be below 10Pa, and sealing the opening of the reaction container by using oxyacetylene flame;
(3) placing the sealed reaction vessel in a high-temperature sintering furnace, heating to 850 ℃ at the speed of 15 ℃/min, then carrying out heat preservation smelting at 850 ℃ for 60min, and then swinging for 30min at the frequency of 5r/min at the swinging angle of 60 degrees;
(4) after the smelting is finished, closing a power supply of the high-temperature sintering furnace, taking out the reaction container, and cooling the reaction container to room temperature in the air to obtain an SnSe-based thermoelectric material ingot;
(5) putting the ingot obtained in the step (4) and Bi into a ball milling tank for ball milling, wherein the mass of the Bi accounts for 40% of that of the ingot, and the ball milling time is 10min, so as to obtain powder with the particle size range of 0.5-500 mu m;
(6) putting the powder obtained in the step (5) into a graphite mold with the diameter of 12.7mm, putting the mold into a hot pressing furnace, vacuumizing to below 10Pa, heating to 350 ℃, pressurizing to 60Mpa, controlling the heating rate at 15 ℃/min and the pressurizing rate at 20Mpa/min, keeping the temperature and the pressure for 10min, and then releasing the pressure and demolding at 20 Mpa/min.
Tests prove that the highest thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750K-800K in the direction perpendicular to the pressure direction reaches 1.05.
The embodiments described above are intended to illustrate the technical solutions of the present invention in detail, and it should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention, and any modification, supplement or similar substitution made within the scope of the principles of the present invention should be included in the protection scope of the present invention.

Claims (11)

1. A preparation method of a polycrystalline SnSe-based thermoelectric material comprises the following steps:
preparing raw materials according to the stoichiometry of the SnSe-based thermoelectric material;
smelting the raw materials to obtain a SnSe-based polycrystalline ingot;
carrying out ball milling on the SnSe-based polycrystal ingot to obtain powder, and then carrying out hot-pressing sintering to obtain a block material;
the method is characterized in that: adding a sintering aid in the SnSe-based polycrystalline ingot ball milling process to perform mixed ball milling;
the sintering aid is at least one of Te, Se, Pb, Br, Sn, Sb and Bi; and the mass of the sintering aid accounts for 5-50% of that of the SnSe-based polycrystalline ingot.
2. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: said SnSe radicalThe chemical structural formula of the thermoelectric material is MxSn1-xSe, wherein M is at least one of Na, Ag, Pb, Cu, Mn, K, Zn, In, Bi and Sb, and x is more than or equal to 0 and less than or equal to 0.5.
3. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: the particle size range of the powder is 0.5-500 mu m.
4. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: the smelting process comprises the following steps: placing the raw material vacuum sealed tube in a quartz tube, placing the quartz tube in a smelting furnace, heating to smelt the raw material, and naturally cooling the quartz tube to room temperature after smelting is finished to obtain a SnSe-based polycrystalline ingot;
preferably, the raw materials are put into a quartz tube, and the quartz tube is vacuumized to be less than or equal to 5Pa and then sealed;
preferably, the smelting furnace is a high-temperature sintering furnace, and a quartz tube swings in the smelting process to uniformly mix the raw materials;
preferably, the temperature is raised to 850-1000 ℃ in the smelting process.
5. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: the hot pressing process comprises the following steps: and putting the powder into a mold, putting the mold into a vacuum hot-pressing sintering furnace, vacuumizing to no more than 10Pa, and carrying out hot pressing.
6. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: the hot-pressing sintering temperature is 350-550 ℃, and the pressure is 50-80 Mpa.
7. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: in the hot-pressing sintering process, the heating rate is 3-30 ℃/min.
8. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: in the hot-pressing sintering process, the pressurizing rate is 1 Mpa/min-30 Mpa/min.
9. The method of making a polycrystalline SnSe-based thermoelectric material of claim 1, wherein: and in the hot-pressing sintering process, the heat preservation and pressure maintaining time is 10-20 min.
10. The method for producing a polycrystalline SnSe-based thermoelectric material according to any one of claims 1 to 9, characterized by: the grain orientation degree of the prepared polycrystalline SnSe-based thermoelectric material is greater than or equal to 0.4.
11. The method for producing a polycrystalline SnSe-based thermoelectric material according to any one of claims 1 to 9, characterized by: the thermoelectric figure of merit of the prepared polycrystalline SnSe-based thermoelectric material at 750K-800K is higher than 0.5.
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