CN112670400A - Preparation method of porous SnTe thermoelectric material - Google Patents
Preparation method of porous SnTe thermoelectric material Download PDFInfo
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- CN112670400A CN112670400A CN202110068392.5A CN202110068392A CN112670400A CN 112670400 A CN112670400 A CN 112670400A CN 202110068392 A CN202110068392 A CN 202110068392A CN 112670400 A CN112670400 A CN 112670400A
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Abstract
The invention belongs to the technical field of thermoelectric materials, and provides a preparation method of a porous SnTe thermoelectric material, which comprises the following steps: respectively weighing Sn powder and Te powder which accord with the stoichiometric ratio, transferring the weighed Sn powder and Te powder into a ball milling tank for ball milling, and synthesizing to obtain pure-phase SnTe powder; preparing the SnTe powder into a porous SnTe thermoelectric block material by using discharge plasma sintering equipment, wherein the pressure intensity of the SnTe powder in the sintering temperature rise stage is controlled to be P1，P1Not less than 4 MPa. According to the invention, the pressure intensity of the discharge plasma sintering temperature rise stage is adjusted, and the porosity is higher when the pressure of the sintering temperature rise stage is higher, so that the thermal conductivity of the material can be effectively reduced, the thermoelectric conversion efficiency of the SnTe thermoelectric material is maximized, the thermoelectric material with a high ZT value is obtained, the energy utilization rate is favorably improved, and resources are saved.
Description
Technical Field
The invention relates to the technical field of thermoelectric materials, in particular to a preparation method of a porous SnTe thermoelectric material.
Background
Over-development and use of fossil energy has caused great damage to the environment in recent years while causing a shortage of non-renewable energy. More than half of the energy of the traditional energy sources can be lost in the form of waste heat in the energy conversion process, so that the energy utilization rate is low, and the resources are wasted.
The thermoelectric material can realize the direct conversion of heat energy and electric energy, and has important significance for waste heat recovery. Therefore, it is most important for the thermoelectric material to improve its thermoelectric conversion efficiency. The thermoelectric conversion efficiency can be expressed as a dimensionless value: ZT ═ S2σ T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity.
The research at present finds that the PbTe-based (lead telluride) thermoelectric material shows excellent thermoelectric performance. However, the high toxicity of Pb makes it difficult to apply PbTe thermoelectric materials in daily life. SnTe (tin telluride) has a similar crystal structure and energy band structure to PbTe, so SnTe is considered as the most promising substitute for PbTe.
However, the intrinsic thermoelectric properties of SnTe are not ideal. This is because SnTe contains high Sn vacancies, resulting in a low seebeck coefficient and high electron thermal conductivity of the material. In addition, Sn atoms have a lighter atomic mass than Pb atoms, so SnTe has a higher lattice thermal conductivity than PbTe. Therefore, it is apparent that a decrease in thermal conductivity is required to increase the ZT value of SnTe.
In the invention patent with the patent number of CN200910092656.X and the patent name of the invention patent of the preparation method of the bismuth tellurium series nano-porous thermoelectric material, bismuth tellurium series material powder and a pore-forming agent are uniformly mixed, and the pore-forming agent is sublimated and volatilized during sintering to form the porous material with a nano-size pore structure. However, the pore-forming agent is easy to introduce other impurities into the material, which is not favorable for the thermoelectric property of the material.
Disclosure of Invention
Aiming at the technical problems in the prior art, the invention provides a preparation method of a porous SnTe thermoelectric material, which regulates and controls the porosity of the thermoelectric material by regulating the pressure intensity in the temperature rise stage of discharge plasma sintering, wherein the higher the pressure intensity in the temperature rise stage of sintering is, the higher the porosity is, so that the thermal conductivity of the material can be effectively reduced, the maximum thermoelectric conversion efficiency of the SnTe thermoelectric material is realized, and the thermoelectric material with a high ZT value is obtained.
Specifically, the method is mainly realized by the following technical scheme:
a preparation method of a porous SnTe thermoelectric material comprises the following steps:
respectively weighing Sn powder and Te powder which accord with the stoichiometric ratio, transferring the weighed Sn powder and Te powder into a ball milling tank for ball milling, and synthesizing to obtain pure-phase SnTe powder;
controlling the pressure intensity of sintering temperature rise stage to be P by using spark plasma sintering equipment1Preparing the SnTe powder into a porous SnTe thermoelectric block material, wherein P is1≥4MPa。
Preferably, the weighed Sn powder and Te powder are transferred into a ball milling tank for ball milling, and pure-phase SnTe powder is synthesized, which specifically comprises the following steps: and transferring the weighed Sn powder and Te powder into a ball milling tank by a mechanical alloying mode, and carrying out ball milling by using an ethanol solution to synthesize pure-phase SnTe powder.
Preferably, the SnTe powder is prepared into a porous SnTe thermoelectric block material by using spark plasma sintering equipment, and the method specifically comprises the following steps:
transferring the SnTe powder into a graphite mold, putting the graphite mold filled with the SnTe powder into a cavity of a spark plasma sintering device, and vacuumizing the reaction cavity;
sintering and heating: the spark plasma sintering equipment is heated at a first temperature rise speed S1The temperature in the reaction chamber is raised from room temperature to a first temperature C1And at a second temperature-rise rate S2The temperature in the reaction cavity is controlled from C1Raising the temperature to a second temperature C2And controlling the pressure intensity in the reaction cavity to be P1，P1≥4MPa；
Controlling the temperature in the reaction chamber to be C by the spark plasma sintering equipment2Cooling to room temperature after the lower heat preservation time t, and controlling the pressure intensity in the reaction cavity to be P in the heat preservation process2，P2Not less than 60MPa, wherein, C1＜C2。
Compared with the prior art, the invention has the following beneficial effects:
1. the method replaces the use of an organic pore-forming agent in the prior art, solves the problems that the pore-forming agent is easy to introduce other impurities into the thermoelectric material and is not beneficial to the thermoelectric performance of the material, and is simple and does not cause other impurity residues;
2. the pressure intensity in the temperature rising stage of the spark plasma sintering is adjusted, so that the porosity of the thermoelectric material is adjusted, the pressure intensity in the temperature rising stage of the sintering is higher, the porosity is higher, the thermal conductivity of the material is lower, and therefore the thermal conductivity of the material can be effectively reduced by adjusting the pressure intensity in the temperature rising stage of the sintering, the thermoelectric conversion efficiency of the SnTe thermoelectric material is maximized, and the thermoelectric material with a high ZT value is obtained.
Drawings
1. FIG. 1 is a schematic diagram comparing an XRD spectrogram of SnTe powder synthesized by mechanical alloying and an SnTe standard PDF card (97-005-) -2489;
2. FIG. 2 shows the pressure intensity P provided by the present invention1The schematic comparison of the XRD spectrogram of the bulk material obtained at 4MPa, 15MPa and 60MPa with SnTe standard PDF card (97-005-;
3. FIG. 3 shows the pressure intensity P provided by the present invention1Scanning electron micrographs of sections of the bulk material obtained at 4MPa (a, b), 15MPa (c, d) and 60MPa (e, f), respectively;
4. FIG. 4 shows the pressure intensity P provided by the present invention1The sample thermal conductivity of the block material obtained by respectively 4MPa, 15MPa and 60MPa changes with the temperature.
Detailed Description
In order to make the core idea of the present invention more clearly understood, the following detailed description will be made with reference to the accompanying drawings.
Example one
The embodiment of the invention provides a preparation method of a porous SnTe thermoelectric material, which takes Sn powder as an Sn source and Te powder as a Te source. 4.7484g of Sn powder and 5.1040g of Te powder are weighed according to the stoichiometric ratio respectively, then the weighed Sn powder and Te powder are transferred into a ball milling tank, 40g of zirconia grinding balls with the diameter of 3mm, 40g of zirconia grinding balls with the diameter of 5mm and 20g of zirconia grinding balls with the diameter of 10mm and 15mL of ethanol solution are added into the ball milling tank, and the volume of the ball milling tank is 50 mL.
And through a mechanical alloying mode, ball-milling Sn powder and Te powder in an ethanol solution, drying and sieving the ball-milled powder to synthesize pure-phase SnTe powder. Specifically, at a speed of 500 rpm, at Ar2Ball milling is carried out for 180min in the atmosphere. After ball milling, drying the mixture in a vacuum oven at the temperature of 100 ℃ for 12h, and sieving the dried mixture to obtain SnTe powder.
As shown in FIG. 1, the phase of the SnTe powder prepared above was tested by an X-ray diffractometer (model No. XRD-6100) testing apparatus manufactured by Shimadzu corporation, Japan. Comparing the XRD spectrogram of the prepared SnTe powder with a standard PDF card (97-005) 2489 of SnTe, all the peaks completely correspond to each other. Therefore, it was confirmed that the SnTe powder prepared by the above method was a pure phase SnTe powder.
And weighing 1.8g of the SnTe powder, putting the SnTe powder into a graphite mold, putting the graphite mold in which the SnTe powder is put into a cavity of discharge plasma sintering equipment, and carrying out vacuum discharge plasma sintering. The sintering system is divided into 3 stages:
1. controlling the temperature rise speed at 50 ℃/min, controlling the sintering pressure strength to be 4MPa, and raising the temperature of a reaction cavity of the discharge plasma sintering equipment from room temperature to 500 ℃;
2. heating the reaction cavity from 500 ℃ to 560 ℃ at a heating rate of 20 ℃/min and a sintering pressure intensity of 4 MPa;
3. keeping at 560 deg.C under 60MPa for 5min, removing pressure, and cooling to room temperature. And taking out to obtain a cylindrical block SnTe thermoelectric material sample.
Example two
The embodiment of the invention also provides a preparation method of another porous SnTe thermoelectric material, and the preparation method of the SnTe powder is the same as that of the first embodiment, and can refer to the first embodiment, and the details are not repeated here.
And weighing 1.8g of the SnTe powder, putting the SnTe powder into a graphite mold, putting the graphite mold in which the SnTe powder is put into a cavity of discharge plasma sintering equipment, and carrying out vacuum discharge plasma sintering. The sintering system is divided into 3 stages:
1. controlling the temperature rise speed at 50 ℃/min, controlling the sintering pressure strength to be 15MPa, and raising the temperature of a reaction cavity of the discharge plasma sintering equipment from room temperature to 500 ℃;
2. heating the reaction cavity from 500 ℃ to 560 ℃ at a heating rate of 20 ℃/min and a sintering pressure intensity of 15 MPa;
3. keeping at 560 deg.C under 60MPa for 5min, removing pressure, and cooling to room temperature. And taking out to obtain a cylindrical block SnTe thermoelectric material sample.
EXAMPLE III
The embodiment of the invention also provides a preparation method of another porous SnTe thermoelectric material, and the preparation method of the SnTe powder is the same as that of the first embodiment, and can refer to the first embodiment, and the details are not repeated here.
And weighing 1.8g of the SnTe powder, putting the SnTe powder into a graphite mold, putting the graphite mold in which the SnTe powder is put into a cavity of discharge plasma sintering equipment, and carrying out vacuum discharge plasma sintering. The sintering system is divided into 3 stages:
1. controlling the temperature rise speed at 50 ℃/min, the sintering pressure strength to be 60MPa, and raising the temperature of a reaction cavity of the discharge plasma sintering equipment from room temperature to 500 ℃;
2. heating the reaction cavity from 500 ℃ to 560 ℃ at a heating rate of 20 ℃/min and a sintering pressure intensity of 60 MPa;
3. keeping at 560 deg.C under 60MPa for 5min, removing pressure, and cooling to room temperature. And taking out to obtain a cylindrical block SnTe thermoelectric material sample.
As shown in FIG. 2, the sintering pressure intensity (i.e., P) applied for stages 1 and 21) Since SnTe porosities are 1%, 17%, and 31% at 4MPa, 15MPa, and 60MPa, respectively, the porosity of the thermoelectric material increases as the pressure strength increases in the controlled sintering temperature rise step, which is contrary to the common knowledge in the art that "the porosity decreases as the pressure strength increases". This phenomenon is caused by plasma generated between powder particles during SPS (spark plasma sintering) sinteringIn the body, the more loose the stack between the powders, the stronger the plasma generated, and the more easily the powders are densified.
The density of the SnTe thermoelectric material samples prepared in the first, second and third examples was measured, and specifically, the cross-sectional morphology of the SnTe thermoelectric material samples prepared under different pressure regimes as described above was analyzed using a scanning electron microscope (model S-4800) manufactured by hitachi, japan. As can be seen from fig. 3, the porosity of the sample increases significantly as the pressure intensity applied in the 1 st and 2 nd stages (i.e., the sintering temperature rise stage) increases during sintering. The porosity of the SnTe thermoelectric material can be effectively adjusted through the method.
The thermal conductivity of the block material at the temperature of 50-550 ℃ is tested by using a laser thermal conductivity meter which is manufactured by German Chinesis resistant company and is in the model number of LFA 457. The thermal conductivity of samples with different porosities varies with temperature, and as shown in fig. 4, when the porosity of the samples is 1%, 17%, and 31%, respectively, the thermal conductivity decreases in sequence, and thus, the thermal conductivity of the samples shows a tendency to decrease significantly as the porosity increases.
In conclusion, the invention provides a preparation method of the porous thermoelectric material, which is simple and feasible and does not introduce impurities. Through adjusting the pressure intensity of SPS sintering intensification stage, can regulate and control the size of thermoelectric material porosity, sintering intensification stage pressure intensity is big more, thermoelectric material's porosity is high more, and porosity is high more, then material thermal conductivity is low more, therefore, through the change of control SnTe block material porosity, regulate and control the material thermal conductivity that influences thermoelectric conversion efficiency, adjust the pore structure of SnTe block material, can effectively reduce material thermal conductivity, and used organic pore-forming agent among the prior art has been replaced, the problem of introducing other impurity in the pore-forming agent makes thermoelectric material easily, be unfavorable for the thermoelectric performance of material has been solved, the method is simple and can not cause other impurity to remain.
The foregoing detailed description of the embodiments of the present invention has been presented for the purpose of illustrating the principles and implementations of the present invention, and the description of the embodiments is only provided to assist understanding of the core concepts of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention.
Claims (3)
1. The preparation method of the porous SnTe thermoelectric material is characterized by comprising the following steps:
respectively weighing Sn powder and Te powder which accord with the stoichiometric ratio, transferring the weighed Sn powder and Te powder into a ball milling tank for ball milling, and synthesizing to obtain pure-phase SnTe powder;
controlling the pressure intensity of sintering temperature rise stage to be P by using spark plasma sintering equipment1Preparing the SnTe powder into a porous SnTe thermoelectric block material, wherein P is1≥4MPa。
2. The method for preparing the porous SnTe thermoelectric material according to claim 1, wherein the Sn powder and the Te powder are weighed and transferred into a ball milling tank for ball milling, and the pure phase SnTe powder is synthesized, which specifically comprises: and transferring the weighed Sn powder and Te powder into a ball milling tank by a mechanical alloying mode, and carrying out ball milling by using an ethanol solution to synthesize pure-phase SnTe powder.
3. The method for preparing a porous SnTe thermoelectric material according to claim 1 or 2, wherein the pressure intensity in the sintering temperature-raising stage is controlled to be P by using a spark plasma sintering device1Preparing the SnTe powder into a porous SnTe thermoelectric block material, wherein P is1Not less than 4MPa, and specifically comprises the following components:
transferring the SnTe powder into a graphite mold, putting the graphite mold filled with the SnTe powder into a cavity of a spark plasma sintering device, and vacuumizing the reaction cavity;
sintering and heating: the spark plasma sintering equipment is heated at a first temperature rise speed S1The temperature in the reaction chamber is raised from room temperature to a first temperature C1And at a second temperature-rise rate S2The temperature in the reaction cavity is controlled from C1Raising the temperature to a second temperature C2And controlling the pressure in the reaction chamber to be strongDegree P1，P1≥4MPa；
Controlling the temperature in the reaction chamber to be C by the spark plasma sintering equipment2Cooling to room temperature after the lower heat preservation time t, and controlling the pressure intensity in the reaction cavity to be P in the heat preservation process2，P2Not less than 60MPa, wherein, C1＜C2。
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| CN114315353A (en) * | 2021-12-30 | 2022-04-12 | 吉林大学 | P type (Bi, Sb)2Te3Controllable preparation method of porous thermoelectric material |
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| TW201325814A (en) * | 2011-12-27 | 2013-07-01 | Ind Tech Res Inst | Methods of manufacturing multi-element thermoelectric alloys |
| CN105304808A (en) * | 2015-09-29 | 2016-02-03 | 涂艳丽 | SnTe-In2Te3 series thermoelectric material and preparation method thereof |
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Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN101478026A (en) * | 2009-01-21 | 2009-07-08 | 清华大学 | Thermoelectric compounds and preparation thereof |
| TW201325814A (en) * | 2011-12-27 | 2013-07-01 | Ind Tech Res Inst | Methods of manufacturing multi-element thermoelectric alloys |
| CN105304808A (en) * | 2015-09-29 | 2016-02-03 | 涂艳丽 | SnTe-In2Te3 series thermoelectric material and preparation method thereof |
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Non-Patent Citations (1)
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| 邢志波: "《SnTe基无铅热电材料的制备工艺与性能优化研究》", 《中国博士学位论文全文数据库 工程科技I辑 2017年》 * |
Cited By (1)
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| CN114315353A (en) * | 2021-12-30 | 2022-04-12 | 吉林大学 | P type (Bi, Sb)2Te3Controllable preparation method of porous thermoelectric material |
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