CN115558997A - Preparation method for improving mechanical properties of bismuth telluride-based thermoelectric material - Google Patents
Preparation method for improving mechanical properties of bismuth telluride-based thermoelectric material Download PDFInfo
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- 229910052797 bismuth Inorganic materials 0.000 title claims abstract description 100
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 title claims abstract description 100
- XSOKHXFFCGXDJZ-UHFFFAOYSA-N telluride(2-) Chemical compound [Te-2] XSOKHXFFCGXDJZ-UHFFFAOYSA-N 0.000 title claims abstract description 100
- 239000000463 material Substances 0.000 title claims abstract description 82
- 238000002360 preparation method Methods 0.000 title claims abstract description 43
- 239000000843 powder Substances 0.000 claims abstract description 116
- 238000003723 Smelting Methods 0.000 claims abstract description 39
- 238000001192 hot extrusion Methods 0.000 claims abstract description 36
- 239000013078 crystal Substances 0.000 claims abstract description 19
- 239000002994 raw material Substances 0.000 claims abstract description 13
- 238000000034 method Methods 0.000 claims abstract description 12
- 238000002156 mixing Methods 0.000 claims abstract description 9
- 238000001125 extrusion Methods 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 21
- 238000002844 melting Methods 0.000 claims description 12
- 230000008018 melting Effects 0.000 claims description 12
- 238000010309 melting process Methods 0.000 claims 2
- 238000009776 industrial production Methods 0.000 abstract description 2
- 230000006866 deterioration Effects 0.000 abstract 1
- 239000011521 glass Substances 0.000 description 40
- 239000000956 alloy Substances 0.000 description 26
- 229910045601 alloy Inorganic materials 0.000 description 23
- 230000000052 comparative effect Effects 0.000 description 20
- 238000005303 weighing Methods 0.000 description 15
- 239000002253 acid Substances 0.000 description 10
- 238000009826 distribution Methods 0.000 description 10
- 239000004615 ingredient Substances 0.000 description 10
- 238000007789 sealing Methods 0.000 description 10
- 239000000126 substance Substances 0.000 description 10
- 238000005406 washing Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 5
- 238000004857 zone melting Methods 0.000 description 3
- 229910002909 Bi-Te Inorganic materials 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 235000012431 wafers Nutrition 0.000 description 2
- 238000005411 Van der Waals force Methods 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000007542 hardness measurement Methods 0.000 description 1
- 238000007731 hot pressing Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000010248 power generation Methods 0.000 description 1
- 239000002243 precursor Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000012216 screening Methods 0.000 description 1
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- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
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- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B1/00—Single-crystal growth directly from the solid state
- C30B1/02—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing
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Abstract
The invention relates to the field of bismuth telluride base thermoelectric materials, and discloses a preparation method for improving the mechanical property of a bismuth telluride base material, aiming at solving the problems of complex process steps, high equipment requirement and high preparation cost of the bismuth telluride base material in the prior art, wherein the preparation method comprises the following steps of (1) mixing raw material powder for preparing bismuth telluride and then smelting in vacuum to obtain a cast ingot; (2) crushing the cast ingot to obtain powder; (3) Carrying out hot extrusion on the powder under a vacuum atmosphere to obtain an extruded crystal bar; and (2) adding the nano SiC into the raw material powder of the bismuth telluride in the step (1), mixing and then smelting, or adding the crushed ingot into the raw material powder in the step (2) and mixing with the powder. The bismuth telluride thermoelectric material prepared by the preparation method has the advantages of no deterioration of power factors, good mechanical properties, simple and convenient preparation process, low requirements on devices, good uniformity among batches of the obtained material, and suitability for industrial production.
Description
Technical Field
The invention relates to the field of bismuth telluride based thermoelectric materials, in particular to a preparation method for improving the mechanical property of a bismuth telluride based thermoelectric material.
Background
The diversity of electrotechnical applications places varying demands on the performance of thermoelectric devices. Different application environments and working targets put different demands on service characteristics such as output performance parameters and reliability of thermoelectric devices. How to improve the thermoelectric conversion efficiency and the mechanical reliability of the thermoelectric device structure is a core problem in the field.
The bismuth telluride crystal structure can be regarded as a hexahedral layered structure having atoms of the same kind on the same layer, with-Te between layers 1 -Bi-Te 2 -Bi-Te 1 Atomic arrangement of-due to-Te 1 -Te 1 The bonding is carried out by means of weak van der Waals force, so that the bonding is easy to dissociate and break along a (0001) plane (a plane vertical to a C axis). The bismuth telluride-based material prepared by the traditional zone melting process has low orientation in the (00 l) crystal plane direction, so that the material has poor mechanical property and processability and the overall reliability of the thermoelectric power generation device is low. At present, the mechanical properties of the bismuth telluride-based material are easily improved by adopting improved smelting, but the problems of complex process steps, high equipment requirement and high preparation cost exist.
For example, in the chinese patent literature, "a p-type bismuth telluride-based alloy material and a method for producing the same" is disclosed, which is published under the publication number CN113161474A, and comprises the following steps: (1) Performing zone melting on the p-type bismuth telluride base alloy precursor to obtain a p-type bismuth telluride base alloy crystal rod; (2) And (2) putting the p-type bismuth telluride-based alloy crystal rod obtained in the step (1) into a hammer mill sieving machine for hammering and sieving to obtain the p-type bismuth telluride-based alloy material. According to the invention, zone melting, crushing, screening and hot pressing are required to improve the orientation of the p-type bismuth telluride-based alloy material in the (00 l) crystal plane direction, so that the mechanical property is improved, and the preparation process is complex and takes long time.
Disclosure of Invention
The invention provides a preparation method for improving the mechanical property of a bismuth telluride-based thermoelectric material, aiming at overcoming the problems of complex process steps, high equipment requirement and high preparation cost of the bismuth telluride-based thermoelectric material in the prior art.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method for improving the mechanical property of a bismuth telluride-based thermoelectric material comprises the following steps:
(1) Mixing raw material powder for preparing bismuth telluride, and smelting in vacuum to obtain an ingot;
(2) Crushing the cast ingot to obtain powder;
(3) Carrying out hot extrusion on the powder under a vacuum atmosphere to obtain an extruded crystal bar;
and (2) adding the nano SiC into the raw material powder of the bismuth telluride in the step (1), mixing and then smelting, or adding the crushed ingot in the step (2) and mixing with the powder.
The invention selects the nano SiC with good mechanical property and excellent electrical property for doping, and the nano SiC doping amount is regulated and controlled to ensure that the nano SiC is uniformly distributed in the bismuth telluride-based material, thereby improving the mechanical property of the bismuth telluride-based thermoelectric material on the premise of ensuring that the power factor is not deteriorated. In the method, the nano SiC can be doped when the raw materials of the bismuth telluride weighed according to the chemical proportion are mixed, and can also be doped with the powder after ingot casting and crushing.
Preferably, the particle size of the nano SiC is 10 to 100nm.
More preferably, the particle size of the nano SiC is 30nm.
Preferably, the doping amount of the nano SiC is not more than 2% of the total mass of the raw material powder of the bismuth telluride.
Along with the increase of the doping amount of the nano SiC, the hardness of the bismuth telluride material is increased, a small amount of doped nano SiC does not cause negative influence on the power factor of the bismuth telluride material, the doped nano SiC also has the function of reducing the thermal conductivity, but the thermoelectric figure of merit of the bismuth telluride material is increased and then decreased, so that the higher the doping amount of the nano SiC is, the better the doping amount is, when the doping amount is less than 2% of the total mass of the bismuth telluride raw material, the better mechanical property effect is achieved on the bismuth telluride material, and the thermoelectric property is not degraded.
Preferably, in the step (1), the bismuth telluride is P-type bismuth telluride or N-type bismuth telluride.
Preferably, in the step (1), the P-type bismuth telluride is Bi 0.5 Sb 1.5 Te 3+x The value range of x is 0-0.05; the N type bismuth telluride is Bi 2 Te 3-y Se y And the value range of y is 0.1-0.4.
More preferably, when the bismuth telluride is P-type bismuth telluride, the doping amount of the nano SiC is not more than 1.2% of the total mass of the raw material powder of the bismuth telluride.
When the doping amount of the nano SiC in the P-type bismuth telluride is not more than 1.2 percent of the total mass, the mechanical property of the P-type bismuth telluride is improved, and the technical effect of improving the thermoelectric property of the P-type bismuth telluride is also achieved.
More preferably, when the bismuth telluride is N-type bismuth telluride, the doping amount of the nano SiC is not more than 0.7% of the total mass of the raw material powder of bismuth telluride.
The influence of the doping of the nano SiC on the thermoelectric property of the N-type bismuth telluride is larger than that of the P-type bismuth telluride, and when the doping amount of the nano SiC is not higher than 0.7%, the N-type thermoelectric property is better.
The method is suitable for improving the mechanical properties of the P-type bismuth telluride and the N-type bismuth telluride.
Preferably, in the smelting process in the step (1), the vacuum degree is less than 2Pa.
Preferably, the melting temperature in the step (1) is 500 to 650 ℃.
Preferably, the smelting process in the step (1) is carried out in a rocking furnace, and the rocking frequency is 3 to 5 times/min.
Preferably, the particle size of the powder crushed in the step (2) is less than 1mm.
Preferably, in the hot extrusion process of the step (3), the vacuum degree is lower than 10Pa, the temperature is not lower than 450 ℃, and the extrusion ratio is not lower than 9.
The crystal face orientation in the bismuth telluride thermoelectric material can be further optimized in the hot extrusion process.
Therefore, the invention has the following beneficial effects: (1) The mechanical property of the material is improved under the condition of ensuring that the power factor of the bismuth telluride thermoelectric material is not deteriorated; (2) The preparation process is simple and convenient, the requirement on the device is not high, the uniformity among the batches of the obtained materials is good, and the industrial production can be realized.
Drawings
Fig. 1 is an XRD pattern of the bismuth telluride thermoelectric material obtained in comparative example 1 and examples 1 and 2 of the present invention.
Fig. 2 is a diagram showing material properties of the bismuth telluride thermoelectric materials obtained in comparative example 1 and examples 1 and 2 of the present invention.
FIG. 3 is a hardness box plot of the bismuth telluride thermoelectric materials obtained in comparative example 1 and examples 1 and 2 of the present invention.
Detailed Description
The invention is further described with reference to the accompanying drawings and specific embodiments.
Comparative example 1
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 Weighing high-purity Bi powder, sb powder and Te powder according to a chemical ratio;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and (3) putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of the vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal rod with the diameter of phi 30mm multiplied by 50 mm.
Example 1
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 The P-type bismuth telluride is prepared by weighing high-purity Bi powder, sb powder and Te powder according to the chemical proportion, nano SiC powder with the mass of 0.75 percent of the total mass of the Bi powder, the Sb powder and the Te powder and nano SiC powder D50The grain diameter is 30nm;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
Example 2
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 Weighing high-purity Bi powder, sb powder and Te powder according to a chemical ratio, weighing nano SiC powder with the mass being 1.20% of the total mass of the Bi powder, the Sb powder and the Te powder, wherein the D50 particle size of the nano SiC powder is 30nm;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
The performance wafers obtained by comparative example 1 and examples 1 and 2 were sliced, and XRD detection was performed on the performance wafers, and the results are shown in fig. 1, and the peak shapes of examples 1 and 2 are similar to those of comparative example 1, which indicates that a small amount of nano SiC doping does not affect the matrix composition. Then, the Zeebeck coefficient and the electric conductivity of the performance piece are detected through a ZEM test, the thermal diffusion coefficient of the performance piece is tested through an LFA test to calculate the thermal conductivity, and finally, the thermoelectric figure of merit (zT) of the material is calculated through a formula, and the result is shown in figure 2, when the doping amount of the nano SiC powder in the P-type bismuth telluride is 0.75% and 1.20%, the thermoelectric figure of merit (zT) of the P-type bismuth telluride material is higher than that of the P-type bismuth telluride which is not doped with the nano SiC powder, and meanwhile, the performance of the doping amount of 1.20% is better than 0.75%. Finally, the hardness of the performance piece is detected by a Vickers hardness tester, and the result is shown in figure 3, and the hardness of the P-type bismuth telluride thermoelectric material is improved along with the increase of the doping amount of the nano SiC powder.
Example 3
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 Weighing high-purity Bi powder, sb powder and Te powder according to a chemical ratio;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1mm, and then adding nano SiC powder with the mass of 1.20% of the total mass of Bi powder, sb powder and Te powder, wherein the D50 particle size of the nano SiC powder is 10nm;
(4) Hot extrusion: and (3) putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of the vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal rod with the diameter of phi 30mm multiplied by 50 mm.
Example 4
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 Weighing high-purity Bi powder, sb powder and Te powder according to a chemical ratio, weighing nano SiC powder with the mass being 2% of the total mass of the Bi powder, the Sb powder and the Te powder, wherein the D50 particle size of the nano SiC powder is 30nm;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with particle size distribution within 1 mm;
(4) Hot extrusion: and (3) putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of the vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal rod with the diameter of phi 30mm multiplied by 50 mm.
Comparative example 2
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 0.5 Sb 1.5 Te 3 Weighing high-purity Bi powder, sb powder and Te powder according to a chemical ratio, and weighing nano SiC powder with the mass being 3% of the total mass of the Bi powder, the Sb powder and the Te powder, wherein the D50 particle size of the nano SiC powder is 30nm;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at 600 ℃ at a swinging speed of 4 times/min to obtain a P-type alloy ingot;
(3) Crushing: crushing the P-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded P-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
Comparative example 3
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 2 Te 2.7 Se 0.3 Weighing high-purity Bi powder, te powder and Se powder according to a chemical ratio;
(2) Smelting: placing the weighed materials in the step (1) into a clean glass tube after acid cleaning, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at the swinging speed of 4 times/min at 700 ℃ to obtain an N-type alloy ingot;
(3) Crushing: crushing the N-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded N-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
Example 5
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 2 Te 2.7 Se 0.3 Weighing high-purity Bi powder, te powder and Se powder according to a chemical ratio, and weighing nano SiC powder with the mass being 0.15% of the total mass of the Bi powder, the Te powder and the Se powder, wherein the D50 particle size of the nano SiC powder is 30nm;
(2) Smelting: placing the weighed material in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at the swinging speed of 4 times/min at 700 ℃ to obtain an N-type alloy ingot;
(3) Crushing: crushing the N-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded N-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
Example 6
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 2 Te 2.7 Se 0.3 The N-type bismuth telluride is prepared by weighing high-purity Bi powder,Te powder and Se powder, and nano SiC powder with the mass of 0.7 percent of the total mass of the Bi powder, the Te powder and the Se powder is weighed, and the D50 particle size of the nano SiC powder is 100nm;
(2) Smelting: placing the weighed material in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at the swinging speed of 4 times/min at 700 ℃ to obtain an N-type alloy ingot;
(3) Crushing: crushing the N-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded N-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
Example 7
A bismuth telluride-based thermoelectric material is prepared by the following steps:
(1) Ingredient smelting/material preparation: preparation of Bi 2 Te 2.7 Se 0.3 Weighing high-purity Bi powder, te powder and Se powder according to a chemical ratio, and weighing nano SiC powder with the mass being 2% of the total mass of the Bi powder, the Te powder and the Se powder, wherein the D50 particle size of the nano SiC powder is 30nm;
(2) Smelting: placing the weighed material in the step (1) into a clean glass tube after acid washing, reducing the vacuum degree in the glass tube to be within 2Pa, then melting and sealing the end opening of the glass tube by oxyhydrogen flame, placing the glass tube into a swinging furnace, and smelting at the swinging speed of 4 times/min at 700 ℃ to obtain an N-type alloy ingot;
(3) Crushing: crushing the N-type alloy cast ingot by a jaw crusher to obtain small-particle-size powder with the particle size distribution within 1 mm;
(4) Hot extrusion: and putting the powder into an extrusion die, and carrying out hot extrusion under the atmosphere of vacuum degree lower than 10Pa, wherein the hot extrusion temperature is 450 ℃, and the extrusion ratio is 10, so as to obtain the extruded N-type crystal bar with the diameter of phi 30mm multiplied by 50 mm.
The ingots obtained in examples 3 to 7 and comparative examples 2 to 3 were also subjected to performance sheet cutting, and their thermoelectric figure of merit zT and hardness were measured as described above.
The results of measuring the thermoelectric figure of merit zT and hardness of examples 1 to 7 and comparative examples 1 to 3 are shown in the following table.
| Item | Thermoelectric figure of merit zT | Vickers Hardness (HV) |
| Comparative example 1 | 1.09 | 52.6 |
| Example 1 | 1.14 | 84.3 |
| Example 2 | 1.16 | 94.3 |
| Example 3 | 1.17 | 93.0 |
| Example 4 | 0.92 | 103.7 |
| Comparative example 2 | 0.84 | 110.4 |
| Comparative example 3 | 1.00 | 62.3 |
| Example 5 | 1.01 | 70.2 |
| Example 6 | 1.00 | 68.9 |
| Example 7 | 0.78 | 98.8 |
As can be seen from the results of the thermoelectric figure of merit zT and hardness measurements, the hardness of examples 1-4 is higher than that of comparative example 1 without adding nano SiC, the Vickers hardness of examples 5-7 is higher than that of comparative example 2, and examples 1-7 have higher thermoelectric figure of merit zT, so the above data can prove that the invention can improve the hardness of P-type bismuth telluride thermoelectric material and N-type bismuth telluride thermoelectric material without causing more negative effects on the thermoelectric performance of the thermoelectric material.
As shown by the hardness changes of comparative examples 1-2 and 4, the hardness of the bismuth telluride thermoelectric material increases with the increase of the doping amount of nano SiC, wherein the thermoelectric figure of merit zT of examples 1-3 is higher than that of comparative example 1, while the thermoelectric figure of merit zT of example 4 is smaller than that of comparative example 1, which shows that when the doping amount of nano SiC is controlled in the range of not more than 1.2%, the doping of nano SiC can improve both the thermoelectric property and the mechanical property of the P-type bismuth telluride material; when the doping amount of the nano SiC is controlled within the range of not more than 2%, the hardness of the P-type bismuth telluride material can be improved on the basis of not influencing the self thermoelectric property; when the doping amount of the nano SiC is 3%, the thermoelectric figure of merit (zT) of the P-type bismuth telluride material is far lower than that of undoped bismuth telluride, and the nano SiC has a large negative effect on the thermoelectric property of the P-type bismuth telluride material. The thermoelectric figure of merit of the example 5 doped with 0.15% SiC is higher than that of the comparative example 3, while the thermoelectric figure of merit of the example 7 is lower than that of the comparative example 3, which shows that when the doping amount of the nano SiC is controlled in the range of not higher than 0.15%, the nano SiC can improve the thermoelectric property of the N-type bismuth telluride material on the basis of improving the mechanical property thereof. Compared with the example 6 added with 100nmSiC, the SiC with the grain diameter of 30nm is added in the example 5, and the thermoelectric figure of merit, zT, and the Vickers hardness are better, so that the SiC with the grain diameter of 30nm is selected to have the best promotion effect on the bismuth telluride material.
Claims (10)
1. A preparation method for improving the mechanical property of a bismuth telluride-based thermoelectric material is characterized by comprising the following steps:
(1) Mixing raw material powder for preparing bismuth telluride, and smelting in vacuum to obtain an ingot;
(2) Crushing the cast ingot to obtain powder;
(3) Carrying out hot extrusion on the powder in a vacuum atmosphere to obtain an extruded crystal bar;
and (2) adding the nano SiC into the raw material powder of the bismuth telluride in the step (1), mixing and then smelting, or adding the crushed ingot in the step (2) and mixing with the powder.
2. The preparation method for improving the mechanical property of the bismuth telluride based thermoelectric material as claimed in claim 1, wherein the grain size of the nano SiC is 10-100 nm.
3. The preparation method for improving the mechanical property of the bismuth telluride-based thermoelectric material as claimed in claim 1 or 2, wherein the doping amount of the nano SiC is not more than 4% of the total mass of the raw material powder of the bismuth telluride.
4. The preparation method for improving the mechanical property of the bismuth telluride-based thermoelectric material as claimed in claim 1, wherein in the step (1), the bismuth telluride is a P-type bismuth telluride or an N-type bismuth telluride.
5.The method for preparing the bismuth telluride-based thermoelectric material as claimed in claim 4, wherein in the step (1), the P-type bismuth telluride is Bi 0.5 Sb 1.5 Te 3+x The value range of x is 0-0.05; the N-type bismuth telluride is Bi 2 Te 3- y Se y And y ranges from 0.1 to 0.4.
6. The preparation method for improving the mechanical property of the bismuth telluride-based thermoelectric material as claimed in claim 1, wherein a vacuum degree in the melting process in the step (1) is less than 2Pa.
7. The preparation method for improving the mechanical property of the bismuth telluride-based thermoelectric material as claimed in claim 1, 4 or 5, wherein the melting temperature in the step (1) is 500-650 ℃.
8. The preparation method for improving the mechanical property of the bismuth telluride-based thermoelectric material as claimed in claim 1, wherein the melting process in the step (1) is performed in a rocking furnace, and the rocking frequency is 3-5 times/min.
9. The preparation method for improving the mechanical property of the bismuth telluride based thermoelectric material as claimed in claim 1, wherein the particle size of the powder crushed in the step (2) is less than 1mm.
10. The preparation method for improving the mechanical properties of the bismuth telluride-based thermoelectric material as claimed in claim 1, wherein in the hot extrusion process in the step (3), the vacuum degree is lower than 10Pa, the temperature is not lower than 450 ℃, and the extrusion ratio is not lower than 9.
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