CN117177646A - Silver sulfide-based thermoelectric material and preparation method thereof - Google Patents
Silver sulfide-based thermoelectric material and preparation method thereof Download PDFInfo
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- 239000000463 material Substances 0.000 title claims abstract description 81
- 229910052946 acanthite Inorganic materials 0.000 title claims abstract description 79
- XUARKZBEFFVFRG-UHFFFAOYSA-N silver sulfide Chemical compound [S-2].[Ag+].[Ag+] XUARKZBEFFVFRG-UHFFFAOYSA-N 0.000 title claims abstract description 79
- 229940056910 silver sulfide Drugs 0.000 title claims abstract description 79
- 238000002360 preparation method Methods 0.000 title abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 139
- 238000001816 cooling Methods 0.000 claims abstract description 70
- 238000000034 method Methods 0.000 claims abstract description 46
- 239000013078 crystal Substances 0.000 claims abstract description 44
- 239000002994 raw material Substances 0.000 claims abstract description 27
- 230000007704 transition Effects 0.000 claims abstract description 27
- 239000000155 melt Substances 0.000 claims abstract description 22
- 238000000137 annealing Methods 0.000 claims abstract description 18
- 238000004321 preservation Methods 0.000 claims abstract description 14
- 230000012010 growth Effects 0.000 claims abstract description 13
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims description 12
- 229910052717 sulfur Inorganic materials 0.000 claims description 12
- 239000011593 sulfur Substances 0.000 claims description 12
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 claims description 11
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 claims description 10
- 229910052709 silver Inorganic materials 0.000 claims description 10
- 239000004332 silver Substances 0.000 claims description 10
- 229910052714 tellurium Inorganic materials 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 5
- 238000011534 incubation Methods 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 2
- 239000010408 film Substances 0.000 description 24
- 230000008859 change Effects 0.000 description 19
- 239000010453 quartz Substances 0.000 description 16
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 16
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- AFCARXCZXQIEQB-UHFFFAOYSA-N N-[3-oxo-3-(2,4,6,7-tetrahydrotriazolo[4,5-c]pyridin-5-yl)propyl]-2-[[3-(trifluoromethoxy)phenyl]methylamino]pyrimidine-5-carboxamide Chemical compound O=C(CCNC(=O)C=1C=NC(=NC=1)NCC1=CC(=CC=C1)OC(F)(F)F)N1CC2=C(CC1)NN=N2 AFCARXCZXQIEQB-UHFFFAOYSA-N 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
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Abstract
The application belongs to the field of new energy devices, and discloses a silver sulfide-based thermoelectric material and a preparation method thereof. The method comprises the following steps: (1) Placing the crucible filled with the raw materials into a crystal growth furnace for heating to obtain a melt; (2) Cooling the first heating zone and the second heating zone respectively, and enabling the transition zone to form a temperature gradient so as to perform first-stage annealing on the melt; performing a second stage anneal on the product from step (2) to form silver sulfide-based crystals in the crucible; the second-stage annealing comprises heat preservation treatment and cooling treatment which are sequentially carried out. The method is simple to operate, and the obtained silver sulfide-based thermoelectric material formed by slicing the silver sulfide-based crystal has good thermoelectric performance and plastic deformation capability.
Description
Technical Field
The application belongs to the field of new energy devices, and particularly relates to a silver sulfide-based thermoelectric material and a preparation method thereof.
Background
In recent years, the progress of social informatization and intelligence has been acceleratedThe flexible electronics industry is developing vigorously, and there is an increasing need for multifunctional green energy collection. Thermoelectric materials are receiving much attention because they can directly convert thermal energy and electrical energy to each other. Compared with the traditional thermoelectric material, the flexible thermoelectric material has the characteristics of cleanness, no pollution, safety, reliability and the like, and has better application prospect in the fields of wearable electronic devices and other flexible electronics. Silver sulfide-based thermoelectric material (Ag 2 X, x=s, te, etc.) is of great interest because of its superior ductility and high hall mobility. However, the current method for preparing the silver sulfide-based thermoelectric material is complicated, and the obtained silver sulfide-based thermoelectric material is poor in thermoelectric performance and plastic deformation capability.
Accordingly, there is still a need for improvements in the current silver sulfide-based thermoelectric materials and methods of preparing the same.
Disclosure of Invention
The present application aims to solve at least one of the technical problems in the related art to some extent.
In one aspect of the present application, the present application provides a method of preparing a silver sulfide-based thermoelectric material, comprising the steps of: (1) Placing the crucible filled with the raw materials into a crystal growth furnace for heating to obtain a melt; the feedstock comprises silver, sulfur and tellurium; the crystal growing furnace is internally provided with a first heating area, a second heating area and a transition area positioned between the first heating area and the second heating area, and the crucible is positioned in the transition area; (2) Cooling the first heating zone and the second heating zone respectively, and forming a temperature gradient in the transition zone so as to perform first-stage annealing on the melt; (3) And (3) carrying out second-stage annealing on the product obtained in the step (2) to form silver sulfide-based crystals in the crucible, wherein the second-stage annealing comprises one-time heat preservation treatment and one-time cooling treatment.
The method comprises the steps of firstly controlling the temperature of a first heating area and a second heating area, placing a crucible containing raw materials in a transition area for heating treatment, enabling the raw materials to be melted to form a melt, then changing the temperature of the first heating area and the temperature of the second heating area, enabling the transition area to form a temperature gradient, enabling the melt to begin nucleation, crystallization and growth from the lower temperature of the transition area to the higher temperature, and then carrying out heat preservation treatment and cooling treatment on the materials obtained by the first annealing treatment to obtain silver sulfide-based crystals (silver sulfide-based thermoelectric materials) in the crucible. The method is simple to operate, a crucible is not required to be moved, and the silver sulfide-based crystal is formed and grown in a temperature gradient area, so that the silver sulfide-based crystal has excellent thermoelectric performance and plastic deformation capacity and can be used on flexible devices.
According to an embodiment of the application, the silver sulfide-based thermoelectric material has the chemical formula Ag 2 S x Te 1-x Wherein x is more than or equal to 0.4 and less than or equal to 0.9.
According to an embodiment of the application, the silver sulfide-based thermoelectric material has a chemical formula of Ag 2 S 0.7 0e 0.3 . The Ag is 2 S 0.7 0e 0.3 The material shows better comprehensive performance
According to an embodiment of the present application, in the step (1), the heating rate of the heating treatment is 1 to 3 ℃/min. The lower heating rate is adopted, so that the crucible is prevented from being cracked due to the too high heating rate when the temperature is increased.
According to an embodiment of the present application, in step (1), the temperature of the heating treatment is 960 to 1050 ℃. Thus, the raw materials can be sufficiently melted, and the burning loss can be reduced.
According to an embodiment of the present application, in the step (1), the heating treatment includes a heating stage and a heat-preserving stage, wherein a heating rate of the heating stage is 1-3 ℃/min, a temperature of the heat-preserving stage is 960-1050 ℃, and a heat-preserving time is 1340-1550min. Thus, the raw materials can be sufficiently melted, and the burning loss can be reduced.
According to an embodiment of the present application, step (2) includes: (2-1) the first heating zone is heated at a temperature-decreasing rate V 1-1 Down to T 1-1 And the second heating zone is cooled at a cooling rate V 2-1 Down to T 2-1 The method comprises the steps of carrying out a first treatment on the surface of the (2-2) the first heating zone is heated at a temperature-decreasing rate V 1-2 Down to T 1-2 And the second heating zone is cooled at a cooling rate V 2-2 Down to T 2-2 The method comprises the steps of carrying out a first treatment on the surface of the (2-3) the first heating zone is heated at a temperature-decreasing rate V 1-3 Down to T and cool down the second heating zone at a cooling rate V 2-3 Lowering to T; wherein the method comprises the steps of，80℃≤T 1-1 -T 2-1 ≤120℃，80℃≤T 1-2 -T 2-2 The temperature is less than or equal to 120 ℃. The step (2) comprises three-stage cooling treatment, which is favorable for slow crystallization of silver sulfide-based crystals, and further forms silver sulfide-based crystals with compact crystal structures.
According to an embodiment of the present application, the temperature reduction in step (2-1) satisfies at least one of the following conditions:
T 1-1 860-900 ℃;
V 1-1 0.4-0.6deg.C/min;
V 2-1 0.8-1.0deg.C/min;
according to an embodiment of the present application, the temperature reduction in step (2-2) satisfies at least one of the following conditions:
T 1-2 670-730 ℃;
V 1-2 0.02-0.04 ℃/min;
V 1-2 0.02-0.04 ℃/min;
according to an embodiment of the present application, the temperature reduction in step (2-3) satisfies at least one of the following conditions:
V 1-3 1-1.5 ℃/min;
V 2-3 0.3-0.5 ℃/min;
t is 500-600 ℃.
According to the embodiment of the application, in the step (3), the temperature of the heat preservation treatment is 500-600 ℃ and the time is 2700-3000min. The heat preservation condition can further promote the growth of silver sulfide-based crystals and promote the thermoelectric performance of the silver sulfide-based thermoelectric material.
According to an embodiment of the present application, in step (3), the cooling process includes: and cooling the first heating area and the second heating area to 21-25 ℃ at a speed of 0.6-0.8 ℃/min respectively and independently. Thus, the thermoelectric performance of the silver sulfide-based thermoelectric material can be further improved.
According to an embodiment of the application, the method further comprises: slicing and/or rolling the silver sulfide-based crystal obtained in the step (3).
In another aspect of the present application, the present application provides a silver sulfide-based thermoelectric material produced by the foregoing method. The silver sulfide-based thermoelectric material has good thermoelectric performance.
According to an embodiment of the application, the thermoelectric figure of merit of the silver sulfide-based thermoelectric material at 600K is not less than 1.36.
Drawings
The foregoing and/or additional aspects and advantages of the application will become apparent and may be better understood from the following description of embodiments taken in conjunction with the accompanying drawings in which:
FIG. 1 is a schematic view of the furnace interior structure of a vertical Bridgman growth furnace in some embodiments;
FIG. 2 is a schematic diagram of an in-furnace temperature field distribution in some embodiments;
FIG. 3 is an X-ray diffraction pattern of a silver sulfide-based thermoelectric material of example 1;
FIG. 4 is a graph showing the relationship between the conductivity and the temperature change of the silver sulfide-based thermoelectric material of example 1;
FIG. 5 is a graph showing the relationship between the thermal conductivity and the temperature change of the silver sulfide-based thermoelectric material of example 1;
fig. 6 is a graph of seebeck coefficient versus temperature change for the silver sulfide-based thermoelectric material of example 1;
FIG. 7 is a graph showing the relationship between the power factor and the temperature change of the silver sulfide-based thermoelectric material of example 1;
FIG. 8 is a graph showing the relationship between the thermoelectric figure of merit and the temperature change of the silver sulfide-based thermoelectric material of example 1;
FIG. 9 is a graph showing the relationship between the conductivity and the temperature change of the silver sulfide-based thermoelectric material of examples 1 to 3;
FIG. 10 is a graph of Seebeck coefficient versus temperature change for the silver sulfide based thermoelectric materials of examples 1-3;
FIG. 11 is a graph showing the power factor versus temperature change for the silver sulfide-based thermoelectric materials of examples 1-3;
fig. 12 is a graph showing the relationship between the thermoelectric figure of merit and the temperature change of the silver sulfide-based thermoelectric material of comparative example 1.
Reference numerals illustrate:
1: a high temperature zone; 2: a temperature gradient zone; 3: a low temperature zone; 100: a first heating zone; 200: a transition zone; 300: a second heating zone; 400: and a crucible.
Detailed Description
Embodiments of the present application are described in detail below. The embodiments described below are exemplary only for explaining the present application and are not to be construed as limiting the present application.
In a first aspect, the present application provides a method of preparing a silver sulfide-based thermoelectric material, comprising the steps of:
(1) Placing the crucible filled with the raw materials into a crystal growth furnace for heating to obtain a melt;
the feedstock comprises silver, sulfur and tellurium; the crystal growing furnace is internally provided with a first heating area, a second heating area and a transition area positioned between the first heating area and the second heating area, and the crucible is positioned in the transition area;
(2) Cooling the first heating zone and the second heating zone respectively, and forming a temperature gradient in the transition zone so as to perform first-stage annealing on the melt;
(3) Performing a second stage anneal on the product from step (2) to form silver sulfide-based crystals in the crucible; the second-stage annealing comprises heat preservation treatment and cooling treatment which are sequentially carried out.
The method provided by the application comprises the steps of placing a crucible containing raw materials in a transition zone for heating treatment, melting the raw materials to form a melt, changing the temperature of the first heating zone and the temperature of the second heating zone, forming a temperature gradient in the transition zone, carrying out first-stage annealing on the melt, enabling the melt to begin nucleation, crystallization and growth from a position with a lower temperature of the transition zone to a position with a higher temperature, and then carrying out heat preservation treatment and cooling treatment on the materials obtained by the first annealing treatment to obtain silver sulfide-based crystals (silver sulfide-based thermoelectric materials) in the crucible. The method is simple to operate, a crucible is not required to be moved, and the silver sulfide-based crystal is formed and grown in a temperature gradient area, so that the silver sulfide-based crystal has excellent plastic deformation capability and thermoelectric performance and can be used on flexible devices.
It is understood that the temperatures of the first heating zone and the second heating zone refer to the temperatures exhibited by the temperature panels of the single crystal growing furnace.
As an example, the crystal growth furnace is a vertical bridgman furnace, and referring to fig. 1, the vertical bridgman furnace has a first heating region 100, a transition region 200, and a second heating region 300. The ratio of the heights of the first heating zone 100, the transition zone 200, and the second heating zone 300 may be 1: (0.5-0.7) to 1. In the process of preparing the silver sulfide-based thermoelectric material, the crucible 400 is positioned in the transition zone 200, the temperatures of the first heating zone 100 and the second heating zone 300 are controlled to be not lower than the melting point of the raw material, so that the raw material positioned in the transition zone 200 is melted to form a melt, then the first heating zone 100 and the second heating zone 300 are respectively subjected to cooling treatment, and the temperature of the first heating zone 100 is controlled to be higher than that of the second heating zone 300 in the cooling process, so that the transition zone 200 forms a temperature gradient zone. Specifically, referring to fig. 2, the first heating zone 100 forms a high temperature zone 1, the second heating zone 200 forms a temperature gradient zone 2, and the second heating zone 300 forms a low temperature zone 3, such that a melt located in the temperature gradient zone 2 is nucleated and grown in a crucible from a direction close to the low temperature zone 3 toward the high temperature zone 1.
The type of the crucible is not particularly limited in the present application, and for example, the crucible may be a pointed cone type quartz crucible.
As an example, a raw material containing silver, sulfur and tellurium may be mixed in a desired ratio and charged into a tapered quartz crucible, and then the tapered quartz crucible is evacuated to a vacuum degree of not more than 1X 10 -4 And sealing the pipe after Pa to further prevent sulfur from volatilizing in the heating process. Alternatively, the sealed tapered quartz crucible may be placed in a quartz tube, and the quartz tube is evacuated to a vacuum level of not higher than 1X 10 -4 And sealing the pipe after Pa so as to further reduce the falling of the conical crucible after cracking in the heating process.
In some embodiments, the silver, sulfur, and tellurium in the feedstock are all powders or granules having a purity of not less than 99.999wt%, thereby reducing the effect of impurities on the crystal.
In some embodiments, the silver sulfide-based thermoelectric material has the formula Ag 2 S x Te 1-x Wherein 0.4.ltoreq.x.ltoreq.0.9, e.g.x is 0.4, 0.5, 0.6, 0.8, 0.9 etc. The sulfur and tellurium atoms in the silver sulfide-based thermoelectric material are randomly occupied on the anion site, so that the better flexibility, the better thermoelectric performance and the lower heat conductivity can be achieved.
Optionally, the silver sulfide-based thermoelectric material has a chemical formula of Ag 2 S 0.7 0e 0.3 . Thus, the thermoelectric performance of the silver sulfide-based thermoelectric material can be improved.
According to the application, in step (1), the raw material in the crucible is heated to form a melt. In some embodiments, the heating treatment may include a temperature increasing stage and a temperature maintaining stage, wherein the heating treatment conditions may be adjusted according to the ratio of silver, sulfur and tellurium in the silver sulfide-based thermoelectric material.
Optionally, the temperature ramp up stage has a temperature ramp up rate of 1-3 ℃/min, such as a temperature ramp up rate of 1 ℃/min, 2 ℃/min, 3 ℃/min, etc. With this lower heating rate, the possibility of crucible explosion can be reduced while the temperature is increased.
Alternatively, the temperature of the incubation period is 960-1050 ℃, e.g., 960 ℃, 970 ℃, 980 ℃, 1000 ℃, 1050 ℃, etc. Thus, the raw materials can be sufficiently melted, and the burning loss can be reduced.
Generally, in step (1), the time required for raising the temperature to the temperature of the incubation period may be 450-550min, for example, 450min, 470min, 500min, 520min, 550min.
Optionally, the incubation period is 1340-1500min, such as 1340min, 1390min, 1440min, 1490min, 1550min, etc. Can make the raw materials fully melted and reduce burning loss.
In the step (1), the temperature of the first heating region and the temperature of the second heating region may be the same or different. Since the purpose of the step (1) is to melt the raw material, from the viewpoint of convenience of operation, the heating temperatures and the heating rates of the first heating zone and the second heating zone are optionally the same, so that the raw material placed in the crucible can be heated uniformly to form a melt.
According to the application, in the step (2), the temperature gradient is formed in the transition zone by respectively carrying out differential cooling on the first heating zone and the second heating zone so as to carry out the first-stage annealing treatment on the melt, thereby promoting the crystallization and growth of the melt.
In some embodiments, step (2) comprises: (2-1) the first heating zone is heated at a temperature-decreasing rate V 1-1 Cooling to a temperature T 1-1 And the second heating zone is cooled at a cooling rate V 2-1 Cooling to a temperature T 2-1 The method comprises the steps of carrying out a first treatment on the surface of the (2-2) the first heating zone is heated at a temperature-decreasing rate V 1-2 Cooling to a temperature T 1-2 And the second heating zone is cooled at a cooling rate V 2-2 Cooling to a temperature T 2-2 The method comprises the steps of carrying out a first treatment on the surface of the (2-3) the first heating zone is heated at a temperature-decreasing rate V 1-3 Cooling to a temperature T, and cooling the second heating zone at a cooling rate V 2-3 Cooling to a temperature T; wherein, T is less than or equal to 80 DEG C 1-1 -T 2-1 At a temperature of 120℃or less, e.g.T 1-1 -T 2-1 80 ℃, 90 ℃, 100 ℃, 120 ℃ and the like; t at 80℃ or less 1-2 -T 2-2 At a temperature of 120℃or less, e.g.T 1-2 -T 2-2 80 ℃, 90 ℃, 100 ℃, 120 ℃ and the like.
The cooling process of (2-1) and (2-2) is generally controlled so that the temperature of the second heating zone is lower than that of the first heating zone, and the melt starts to nucleate, crystallize and grow from the lower temperature position of the temperature gradient zone to the higher temperature position; in (2-3), the temperature of the second heating zone is equalized with the temperature of the first heating zone at the end of the temperature reduction, and the growth of the silver sulfide-based crystal is completed. Therefore, the three-stage cooling treatment is adopted, so that the slow crystallization of the silver sulfide-based crystal is facilitated, and the silver sulfide-based crystal with a compact crystal structure is further obtained.
In step (2-1), optionally, the temperature T of the first heating zone 1-1 At 860-900 ℃, e.g. T 1-1 860 ℃, 870 ℃, 880 ℃, 890 ℃, 900 ℃ and the like.
Optionally, the cooling rate V of the first heating zone 1-1 From 0.4 to 0.6℃per minute, e.g.V 1-1 0.4 ℃/min, 0.5 ℃/min, 0.6 ℃/min, etc.
Optionally, the temperature T of the second heating zone 2-1 750-810 ℃, e.g. T 2-1 750 ℃, 760 ℃, 780 ℃, 790 ℃, 810 ℃ and the like.
Optionally, the cooling rate V of the second heating zone 2-1 From 0.8 to 1.0℃per minute, e.g.V 2-1 0.8 ℃/min, 0.9 ℃/min, 1 ℃/min, etc.
Optionally, the cooling time is 220-260min, such as 220min, 230min, 240min, 250min, 260min, etc.
In step (2-2), optionally, the temperature T of the first heating zone 1-2 670-730 deg.C, such as 670 deg.C, 680 deg.C, 690 deg.C, 700 deg.C, 730 deg.C, etc.
Optionally, the cooling rate V of the first heating zone 1-2 From 0.02 to 0.04℃per minute, e.g.V 1-2 0.02 ℃/min, 0.03 ℃/min, 0.04 ℃/min, etc.
Optionally, the temperature T of the second heating zone 2-2 At 570-630 ℃, e.g. T 2-1 570 ℃, 580 ℃, 590 ℃, 600 ℃, 630 ℃ and the like.
Optionally, the cooling rate V of the second heating zone 2-2 From 0.02 to 0.04℃per minute, e.g.V 1-2 0.02 ℃/min, 0.03 ℃/min, 0.04 ℃/min, etc.
Optionally, the cooling time is 5300-5500min, such as 5300min, 5350min, 5400min, 5450min, 5500min, etc.
In step (2-3), the temperature T of the first heating zone and the second heating zone is optionally 500-600deg.C, such as T500 deg.C, 520 deg.C, 550 deg.C, 580 deg.C, 600 deg.C, etc.
Optionally, the cooling rate V of the first heating zone 1-3 1-1.5 ℃/min, e.g. V 1-3 1 ℃/min, 1.2 ℃/min, 1.5 ℃/min, etc.
Optionally, the cooling rate V of the second heating zone 2-3 From 0.3 to 0.5℃per minute, e.g.V 1-3 0.3 ℃/min, 0.4 ℃/min, 0.5 ℃/min, etc.
Optionally, the cooling time is 100-140min, such as 100min, 110min, 120min, 1300min, 140min, etc.
According to the application, in the step (3), the product obtained in the step (2) is subjected to a second-stage annealing to form silver sulfide-based crystals in the crucible, wherein the second-stage annealing treatment comprises a heat-preserving treatment and a cooling treatment which are carried out once.
In some embodiments, the temperature of the soak treatment (i.e., the temperature of the first heating zone, the second heating zone) is 500-600 ℃, e.g., 500 ℃, 520 ℃, 560 ℃, 580 ℃, 600 ℃, etc., for a time of 2700-3000 minutes, e.g., 2700 minutes, 2880 minutes, 2900 minutes, 3000 minutes, etc. The temperature and time of the heat preservation treatment are controlled within the range, so that the residual stress in the silver sulfide-based crystal is eliminated, the grain size of the silver sulfide-based crystal is stabilized, the grains of the silver sulfide-based crystal can be thinned, the structure and the components of the silver sulfide-based crystal are uniform, and the thermoelectric performance of the silver sulfide-based thermoelectric material is further improved.
In some embodiments, the cooling process, the first heating zone and the second heating zone are each independently cooled to 21-25 ℃ at a cooling rate of 0.6-0.8 ℃/min, such as a cooling rate of 0.6 ℃/min, 0.7 ℃/min, 0.8 ℃/min, etc. Thus, the thermoelectric performance of the silver sulfide-based thermoelectric material can be further improved.
Optionally, the cooling time of the cooling treatment is 700-750min, such as 700min, 720min, 750min.
In the heat preservation treatment, the temperatures of the first heating area and the second heating area can be the same; in the cooling treatment, the temperatures and the cooling rates of the first heating region and the second heating region may be the same. Therefore, the temperature control programs of the first heating area and the second heating area can be synchronously controlled, and the preparation process is simplified.
It is understood that since the silver sulfide-based crystal, i.e., the silver sulfide-based thermoelectric material, is formed in the crucible, it has a shape conforming to that of the crucible. The silver sulfide-based thermoelectric material directly formed in the crucible can be further processed into other shapes in order to meet different application requirements. From the standpoint of satisfying the use requirements of the flexible device, in some embodiments, the method further comprises slicing and/or roll-pressing the silver sulfide-based crystal formed in the crucible. The slicing may be performed by using a wire cutting machine, for example.
In some embodiments, the silver sulfide-based thermoelectric material is a thermoelectric film. Alternatively, the thermoelectric film has a thickness of 0.01-0.2mm, such as 0.01mm, 0.05mm, 0.1mm, 0.15mm, 0.2mm, etc.
In a second aspect of the present application, there is provided a silver sulfide-based thermoelectric material produced by the above-described method. The silver sulfide-based thermoelectric material prepared by the method provided by the application has better thermoelectric performance.
In some embodiments, the silver sulfide-based thermoelectric material has a thermoelectric figure of merit at 600K of not less than 1.36, alternatively, the silver sulfide-based thermoelectric material has a thermoelectric figure of merit at 600K of from 1.36 to 1.5. The thermoelectric material based on silver sulfide has a thermoelectric figure of merit of not less than 1.36 at 600K, and the higher thermoelectric figure of merit is beneficial to the application in flexible devices.
The following description of the present application is made by way of specific examples, which are given for illustration of the present application and should not be construed as limiting the scope of the application. The examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the specifications of the product.
The crystal growth furnace used for preparing the silver sulfide-based thermoelectric material in the following examples and comparative examples was a vertical Bridgman growth furnace model PTL-HT-B, available from Hefei materials Co.
Example 1
Mixing three powders of silver, sulfur and tellurium with purity of 99.999wt% at a molar ratio of 2:0.7:0.3 to form a raw material with mass sum of 15g, loading the raw material into a cone-shaped quartz crucible, and vacuumizing to 1×10 -4 Pa, sealing the tube with flame, loading the quartz crucible into the quartz tube, and vacuumizing the quartz tube to 1×10 -4 And (5) performing flame tube sealing after Pa. Then, the quartz crucible filled with the raw materials is placed in a transition zone of a vertical Bridgman furnace, the temperature of the first heating zone, the transition zone and the second heating zone is raised to 1000 ℃ within 500min under the heating condition, and the temperature is kept for 1440min, wherein the heating rate in the heating process is controlled to be 2 ℃/min, so that the raw materials are completely meltedAnd (5) melting to obtain a melt.
The first heating zone and the second heating zone are respectively subjected to first-stage annealing and second-stage annealing to form Ag in the crucible 2 S 0.7 Te 0.3 Crystal (Ag) 2 S 0.7 Te 0.3 Thermoelectric material). Wherein, the temperature and time control of the annealing process are shown in Table 1.
The thermoelectric material was cut by a wire-cut electric discharge machine to obtain a thermoelectric film having a thickness of 0.15 mm.
TABLE 1
Example 2
Preparation of Ag according to the methods of example 1 2 S 0.7 Te 0.3 Thermoelectric materials except that the thermoelectric materials were cut using a wire saw to obtain a thermoelectric film having a thickness of 0.05 mm.
Example 3
Preparation of Ag according to the methods of example 1 2 S 0.7 Te 0.3 Thermoelectric materials except that the thermoelectric materials were cut using a wire saw to obtain a thermoelectric film having a thickness of 0.10 mm.
Example 4
A thermoelectric material was prepared in accordance with the method of example 1, except that three kinds of powders of silver, sulfur and tellurium were compounded in a molar ratio of 2:0.4:0.6 to form a raw material having a mass total of 15g, and Ag was obtained in a crucible 2 S 0.4 Te 0.6 Crystal (Ag) 2 S 0.4 Te 0.6 Thermoelectric material), and finally cutting the thermoelectric material by a wire cutting machine to obtain the thermoelectric film with the thickness of 0.15 mm.
Example 5
A thermoelectric material was prepared in accordance with the method of example 1, except that three kinds of powders of silver, sulfur and tellurium were compounded in a molar ratio of 2:0.9:0.1 to form a raw material having a mass total of 15g, and Ag was obtained in a crucible 2 S 0.9 Te 0.1 Crystal (Ag) 2 S 0.9 Te 0.1 Thermoelectric material), and finally cutting the thermoelectric material by a wire cutting machine to obtain the thermoelectric film with the thickness of 0.15 mm.
Comparative example 1
Mixing three powders of silver, sulfur and tellurium with purity of 99.999wt% at a molar ratio of 2:0.7:0.3 to obtain 15g raw material, loading into a cone-shaped quartz crucible, and vacuumizing to 1×10 -4 Pa, sealing the tube with flame, loading the quartz crucible into the quartz tube, and vacuumizing the quartz tube to 1×10 -4 And (5) performing flame tube sealing after Pa. And then, placing the quartz crucible filled with the raw materials in a vertical Bridgman transition zone, heating the first heating zone, the transition zone and the second heating zone to 1000 ℃ under heating conditions, and preserving heat for 1440min, wherein the heating rate in the heating process is controlled at 2 ℃/min so as to completely melt the raw materials and obtain a melt.
And respectively cooling the first heating area and the second heating area, wherein the specific process of the cooling treatment is as follows: cooling the first heating zone and the second heating zone to 550 ℃ within 5780min, keeping the temperature of the first heating zone and the second heating zone the same during the cooling process, then preserving the heat of the materials obtained by cooling at 550 ℃ for 2880min, and finally cooling the materials obtained by heat preservation to 20 ℃ within 720min to obtain Ag 2 S 0.7 Te 0.3 Crystal (Ag) 2 S 0.7 Te 0.3 Thermoelectric material).
The thermoelectric material was cut by a wire-cut electric discharge machine to obtain a thermoelectric film having a thickness of 0.15 mm.
Test case
The thermoelectric films obtained in examples 1 to 5 and comparative example 1 were subjected to the following respective performance tests.
1. Conductivity, resistance, seebeck coefficient, and power factor
The testing method comprises the following steps: the electrical test system ZEM-3, manufactured by ULVAC-RIKO design, was used to obtain the resistance, conductivity, seebeck coefficient, and power factor.
Test conditions: the temperature range is 300K-673K.
2. Thermal conductivity
The testing method comprises the following steps: produced by German Chi-resistant Co Ltd is measured by an LFA-467 laser.
Test conditions: the temperature ranges from 300K to 650K.
3. Phase analysis
The sample was collected for phase analysis by using a MiniFlex600 type X-ray powder diffractometer manufactured by RIGAKU corporation of Japan. The basic parameters of the X-ray diffractometer are set as follows: the fixed target monochromatic light source is Cu-K alpha ray with wavelengthTube voltage 40kV, tube current 20mA, scanning range 10-90 degrees, and scanning step size 0.02.
4. Thermoelectric figure of merit
The testing method comprises the following steps: the formula zt= (S) is combined according to the resistance, seebeck coefficient, thermal conductivity, and the like 2 And sigma.T)/k is calculated to obtain a thermoelectric figure of merit, wherein S is the Seebeck coefficient, sigma is the electrical conductivity, k is the thermal conductivity, and T is the temperature.
FIG. 3 is Ag obtained in example 1 2 S 0.7 Te 0.3 Thermoelectric material X-ray diffraction pattern, as can be seen from the figure: is cubic Ag at the 2 theta of 30 DEG + -1 DEG 2 S 0.7 Te 0.3 Characteristic peaks of (2) indicating that Ag 2 S 0.7 Te 0.3 The thermoelectric material has a cubic phase.
Fig. 4 is a graph of the conductivity versus temperature change of the thermoelectric film obtained in example 1, from which it can be seen that the conductivity of the thermoelectric film decreases with increasing temperature, exhibiting typical metallic conductive behavior.
FIG. 5 is a graph showing the relationship between the thermal conductivity and the temperature change of the thermoelectric film obtained in example 1, from which Ag can be seen 2 S 0.7 Te 0.3 The thermal conductivity of (a) is less changed with the rise of temperature, and overall, ag 2 S 0.7 Te 0.3 Exhibits a lower thermal conductivity due to cubic phase Ag 2 S 0.7 Te 0.3 Has a highly symmetrical crystal structure.
Fig. 6 is a graph showing the relationship between the seebeck coefficient and the temperature change of the thermoelectric film obtained in example 1, and it can be seen from the graph that the seebeck coefficient decreases with a decrease in temperature.
Fig. 7 is a graph of the power factor versus temperature change of the thermoelectric film obtained in example 1, from which it can be seen that the power factor increases with increasing temperature, and the change of the power factor with temperature after increasing the temperature to 600K is small, indicating that the thermoelectric film has a superior power factor.
FIG. 8 is a graph showing the relationship between the thermoelectric figure of merit and the temperature change of the thermoelectric film obtained in example 1, from which it can be seen that the thermoelectric figure of merit increases with increasing temperature, indicating that the thermoelectric film has a better thermoelectric performance.
FIG. 9 is a graph showing the relationship between the electrical conductivity and the temperature change of the thermoelectric thin film obtained in examples 1 to 3, from which it can be seen that the electrical conductivity and the thickness of the thermoelectric thin film are inversely proportional, indicating that the thermoelectric performance is reduced by decreasing the thickness of the thermoelectric material.
Fig. 10 is a graph of seebeck coefficient versus temperature change for the thermoelectric films obtained in examples 1-3, from which it can be seen that the seebeck coefficient for thermoelectric films of different thicknesses decreases with increasing temperature.
FIG. 11 is a graph showing the power factor versus temperature change of the thermoelectric film obtained in examples 1-3, from which it can be seen that the power factor of the thermoelectric film is inversely related to the thickness.
Fig. 12 is a graph of the thermoelectric figure of merit of the thermoelectric film obtained in comparative example 1 versus the change in temperature, from which it can be seen that the thermoelectric figure of merit increases with the increase in temperature, but, in comparison with fig. 8, it can be seen that the thermoelectric figure of merit of the thermoelectric film obtained by the method of the present application is higher than that of the thermoelectric film of comparative example 1.
In conclusion, the thermoelectric material prepared by the method has better thermoelectric performance.
In the description of the present specification, reference to the term "one embodiment" or the like means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the application. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction. In addition, it should be noted that, in this specification, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated.
While embodiments of the present application have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the application, and that variations, modifications, alternatives and variations may be made to the above embodiments by one of ordinary skill in the art within the scope of the application.
Claims (12)
1. A method of preparing a silver sulfide-based thermoelectric material, comprising the steps of:
(1) Placing the crucible filled with the raw materials into a crystal growth furnace for heating treatment to obtain a melt;
the feedstock comprises silver, sulfur and tellurium; the crystal growing furnace is internally provided with a first heating area, a second heating area and a transition area positioned between the first heating area and the second heating area, and the crucible is positioned in the transition area;
(2) Cooling the first heating zone and the second heating zone respectively, and forming a temperature gradient in the transition zone so as to perform first-stage annealing on the melt;
(3) Performing a second stage anneal on the product from step (2) to form silver sulfide-based crystals in the crucible; the second-stage annealing comprises heat preservation treatment and cooling treatment which are sequentially carried out.
2. The method of claim 1, wherein the silver sulfide-based thermoelectric material has a chemical formula Ag 2 S x Te 1-x Wherein x is more than or equal to 0.4 and less than or equal to 0.9;
optionally, the silver sulfide-based thermoelectric material has a chemical formula of Ag 2 S 0.7 0e 0.3 。
3. The method according to claim 1 or 2, wherein in step (1), the heating treatment comprises a temperature raising stage and a heat preservation stage, the temperature raising rate of the temperature raising stage is 1-3 ℃/min, the temperature of the heat preservation stage is 960-1050 ℃, and the heat preservation time is 1340-1550min.
4. The method according to claim 1 or 2, wherein step (2) comprises:
(2-1) the first heating zone is heated at a temperature-decreasing rate V 1-1 Cooling to a temperature T 1-1 And the second heating zone is cooled at a cooling rate V 2-1 Cooling to a temperature T 2-1 ；
(2-2) the first heating zone is heated at a temperature-decreasing rate V 1-2 Cooling to a temperature T 1-2 And the second heating zone is cooled at a cooling rate V 2-2 Cooling to a temperature T 2-2 ；
(2-3) the first heating zone is heated at a temperature-decreasing rate V 1-3 Cooling to a temperature T, and cooling the second heating zone at a cooling rate V 2-3 Cooling to a temperature T;
wherein, T is less than or equal to 80 DEG C 1-1 -T 2-1 ≤120℃，80℃≤T 1-2 -T 2-2 ≤120℃。
5. The method of claim 4, wherein the cooling in step (2-1) satisfies at least one of the following conditions:
T 1-1 860-900 ℃;
V 1-1 0.4-0.6deg.C/min;
V 2-1 0.8-1.0deg.C/min.
6. The method of claim 4, wherein the cooling in step (2-2) satisfies at least one of the following conditions:
T 1-2 670-730 ℃;
V 1-2 0.02-0.04 ℃/min;
V 2-2 0.02-0.04 ℃/min.
7. The method of claim 4, wherein the cooling in step (2-3) satisfies at least one of the following conditions:
V 1-3 1-1.5 ℃/min;
V 2-3 0.3-0.5 ℃/min;
t is 500-600 ℃.
8. The method according to claim 1 or 2, wherein in step (3), the temperature of the incubation treatment is 500-600 ℃ for 2700-3000min.
9. The method according to claim 1 or 2, wherein in step (3), the cooling treatment comprises: and cooling the first heating area and the second heating area to 21-25 ℃ at a cooling rate of 0.6-0.8 ℃/min respectively and independently.
10. The method as recited in claim 1, further comprising:
slicing and/or rolling the silver sulfide-based crystal obtained in the step (3).
11. A silver sulfide-based thermoelectric material produced by the method of any one of claims 1 to 10.
12. The silver sulfide-based thermoelectric material according to claim 11, wherein the silver sulfide-based thermoelectric material has a thermoelectric figure of merit of not less than 1.36 at 600K.
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