CN114203893A - In-situ coherent composite thermoelectric material and preparation method and application thereof - Google Patents

In-situ coherent composite thermoelectric material and preparation method and application thereof Download PDF

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CN114203893A
CN114203893A CN202111530297.9A CN202111530297A CN114203893A CN 114203893 A CN114203893 A CN 114203893A CN 202111530297 A CN202111530297 A CN 202111530297A CN 114203893 A CN114203893 A CN 114203893A
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powder
situ
thermoelectric material
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林元华
周志方
杨岳洋
许于帅
南策文
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Tsinghua University
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    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/01—Manufacture or treatment
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/10—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/855—Thermoelectric active materials comprising inorganic compositions comprising compounds containing boron, carbon, oxygen or nitrogen

Abstract

The invention discloses an in-situ coherent composite thermoelectric material and a preparation method and application thereof, wherein the chemical formula of the in-situ coherent composite thermoelectric material is (1-y) Cu2+xSe‑yBi1‑(a+b)PbaCabCuSeO, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0<a≤0.1，0<b is less than or equal to 0.1. Therefore, the in-situ coherent composite thermoelectric material has excellent thermoelectric performance and high stability.

Description

In-situ coherent composite thermoelectric material and preparation method and application thereof
Technical Field
The invention belongs to the field of thermoelectric ceramic materials, and particularly relates to an in-situ coherent composite thermoelectric material and a preparation method and application thereof.
Background
With the rapid development of global economy, the shortage of non-renewable resources (such as coal, oil, and natural gas) and the increasing increase of environmental pollution have become problems that human society needs to face together. To solve this problem, scientific and technical personnel in various countries are working on developing new clean energy and improving the existing technology to improve the conversion efficiency of energy. According to incomplete statistics, most energy sources in industrial production and daily life cannot be fully utilized, and more than 60% of the energy is consumed in the form of waste heat. If the waste heat can be effectively utilized, the utilization rate of energy can be greatly improved. Based on the transport characteristics of microscopic current carriers and phonons in the material, the thermoelectric material has the capability of realizing direct interconversion of heat energy (temperature difference) and electric energy; and the thermoelectric device is composed of all-solid-state components, has the advantages of simple structure, safety, reliability, low maintenance cost, wide application range and the like, and makes the related research fields attract attention.
Based on the Seebeck effect and the Peltier effect, the thermoelectric device has good application prospects in the aspects of thermoelectric power generation and solid-state refrigeration. Thermoelectric power generation devices have an irreplaceable position in power generation, particularly in the fields of military affairs, space exploration and the like. For example, the radioactive isotope thermoelectric generator provides power to ensure the space detector to work normally; the temperature difference conversion power generation of industrial waste heat and automobile exhaust waste heat is also an important means for improving the energy utilization rate and the atmospheric environment. In the aspect of refrigeration, the thermoelectric refrigeration device has the advantages of variable volume, no noise, no need of refrigeration medium and the like, and is widely applied to the aspects of movable refrigerators, portable air conditioners, chip refrigeration and the like.
The performance of thermoelectric materials is evaluated by a dimensionless thermoelectric figure of merit (ZT), which is expressed as ZT ═ S2σ T/κ. Wherein S is a Seebeck coefficient, σ is electrical conductivity, κ is thermal conductivity, and T is absolute temperature. Therefore, a good thermoelectric material needs to have high seebeck coefficient and electrical conductivity and low thermal conductivity. Fast ion conductor Cu2Se has high electrical conductivity, low thermal conductivity and excellent thermoelectric property, but the Se has poor stability and is difficult to apply in practice; the layered oxygen-containing compound BiCuSeO has a high Seebeck coefficient and a low thermal conductivity, and is excellent in high temperature and chemical stability, but the electrical conductivity is low.
Therefore, the existing thermoelectric materials are in need of improvement.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art. Therefore, an object of the present invention is to provide an in-situ coherent composite thermoelectric material, a preparation method and applications thereof, wherein the in-situ coherent composite thermoelectric material has both excellent thermoelectric performance and high stability.
In one aspect of the invention, an in-situ coherent composite thermoelectric material is presented. According to an embodiment of the present invention, the in-situ coherent composite thermoelectric material has a chemical formula of (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0<a≤0.1，0<b≤0.1。
The in-situ coherent composite thermoelectric material has a chemical formula of (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO, wherein Cu2+xCu with Se being Cu excess x2Se，Bi1-(a+b)PbaCabCuSeO is BiCuSeO with Pb and Ca elements doped in Bi position by a content and b content respectively, and Cu is selected2+xSe (x is more than or equal to 0 and less than or equal to 0.02) and Bi1-(a+b)PbaCabCuSeO(0<a≤0.1，0<b is less than or equal to 0.1), and the two have approximate carrier concentration, so that an effective composite effect is easily generated, thereby effectively scattering phonons, reducing the thermal conductivity, simultaneously not blocking the transport of the carriers, and being beneficial to the improvement of the thermoelectric performance. Meanwhile, Bi in the composite thermoelectric material1-(a+b)PbaCabThe molar fraction of CuSeO is 5-30%, namely y is more than or equal to 0.05 and less than or equal to 0.3, and the inventor finds that if y is less than 0.05, the main phase of the composite sample is Cu with poor stability2Se, the stability of the obtained sample is poor; and if y is more than 0.3, the carrier concentration of the obtained composite sample is too high, so that the Seebeck coefficient is reduced, the thermal conductivity is improved, and the thermoelectric performance is reduced. Thus, Bi of the present application is used1-(a+b)PbaCabCuSeO mole fraction, and the obtained in-situ coherent composite thermoelectric material has more excellent high-temperature and chemical stability. In summary, the in-situ co-generation method of the present applicationThe grid composite thermoelectric material has excellent thermoelectric performance and high stability.
In addition, the in-situ coherent composite thermoelectric material according to the above embodiment of the present invention may also have the following additional technical features:
in some embodiments of the invention, 0.01 ≦ x ≦ 0.02, 0.05 ≦ y ≦ 0.25, 0.03 ≦ a ≦ 0.06, 0.06 ≦ b ≦ 0.1. Therefore, the in-situ coherent composite thermoelectric material has excellent thermoelectric performance and high stability.
In some embodiments of the present invention, 0.05 ≦ y ≦ 0.2. Therefore, the average thermoelectric figure of merit of the in-situ coherent composite thermoelectric material can exceed 1.0 in the medium-high temperature region (473K-973K), the material is suitable for the practical application of waste heat power generation or thermoelectric refrigeration in the medium-high temperature region, and the stability of the material is high.
In some embodiments of the present invention, b is 0.06. Therefore, the in-situ coherent composite thermoelectric material has excellent thermoelectric performance and high stability.
In a second aspect of the invention, the invention provides a method of making the above-described in situ coherent composite thermoelectric material. According to an embodiment of the invention, the method comprises:
(1) mixing Bi powder and Bi2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder and tabletting to obtain a green body;
(2) heating the green body so as to enable the green body to perform self-propagating reaction to obtain an in-situ coherent composite phase forming sample;
(3) and grinding the phase forming sample, and then performing spark plasma sintering to obtain the in-situ coherent composite thermoelectric material.
According to the method for preparing the in-situ coherent composite thermoelectric material, provided by the embodiment of the invention, Bi powder and Bi are mixed2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder, tabletting, heating the green compact obtained by tabletting to generate self-propagating reaction to generate (1-y) Cu2+xSe-yBi1-(a+b)PbaCabThe CuSeO in-situ coherent composite phase forming sample is a loose block and is difficult to be practically applied, and the CuSeO in-situ coherent composite phase forming sample is formed byAnd (4) after the phase sample is ground, performing spark plasma sintering to obtain the compact in-situ coherent composite thermoelectric material. The raw materials used in the method are the existing commercially available simple substance and oxide raw material powder, the raw materials are easy to obtain, the preparation process is simple, the requirements on experimental equipment and places are low, and the method is favorable for large-scale and industrial production. Meanwhile, the in-situ coherent composite thermoelectric material prepared by the method has excellent thermoelectric performance and high stability.
In addition, the method for preparing the in-situ coherent composite thermoelectric material according to the above embodiment of the present invention may further have the following additional technical features:
in some embodiments of the invention, in step (1), the Bi powder, the Bi2O3The molar ratio of the powder, the Se powder, the Cu powder, the PbO powder and the CaO powder is (y (1-a-b)/3): (y (1-a-b)/3): 1: (2+ x-xy-y): ya: yb, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and 0<a≤0.1，0<b is less than or equal to 0.1. Therefore, the obtained in-situ coherent composite thermoelectric material has excellent thermoelectric performance and high stability.
In some embodiments of the present invention, in the step (1), the pressure of the compressed tablet is 3 to 6 MPa. Thereby, the contact between the powders can be made more sufficient, thereby facilitating the self-propagating reaction to occur.
In some embodiments of the present invention, in the step (2), the heating temperature is 400-600 ℃ and the heating time is 1-2 min. Thereby, the self-propagating reaction of the green body is facilitated.
In some embodiments of the invention, in the step (3), the sintering temperature is 873-973K, the sintering pressure is 40-50 MPa, and the heat preservation time is 3-5 min. Therefore, the compact in-situ coherent composite thermoelectric material is obtained.
In a third aspect of the invention, a thermoelectric device is presented. According to an embodiment of the present invention, the thermoelectric device comprises the in-situ coherent composite thermoelectric material described above or the in-situ coherent composite thermoelectric material obtained by the method described above. Therefore, the thermoelectric device has excellent thermoelectric performance and longer service life, and has good application prospects in the aspects of thermoelectric power generation and solid-state refrigeration.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
Drawings
The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
FIG. 1 is a schematic flow diagram of a method for preparing the above-described in situ coherent composite thermoelectric material according to one embodiment of the present invention;
FIG. 2 is an XRD pattern of the product obtained from the preparation of example 1;
FIG. 3 is an XRD pattern of the product obtained from the preparation of example 2;
FIG. 4 is a sectional SEM backscattering view of the product prepared in example 3;
FIG. 5 is the average ZT value of the product prepared in example 4.
Detailed Description
The embodiments described below with reference to the drawings are illustrative and intended to be illustrative of the invention and are not to be construed as limiting the invention.
In a first aspect of the invention, an in-situ coherent composite thermoelectric material is presented. According to the embodiment of the invention, the chemical formula of the in-situ coherent composite thermoelectric material is (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0<a≤0.1，0<b≤0.1。
The inventors found that the chemical formula is (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO, wherein Cu2+xCu with Se being Cu excess x2Se，Bi1-(a+b)PbaCabCuSeO is BiCuSeO with Pb and Ca elements doped in Bi position by a content and b content respectively, and Cu is selected2+xSe (x is more than or equal to 0 and less than or equal to 0.02) and Bi1-(a+b)PbaCabCuSeO(0<a≤0.1，0<b is less than or equal to 0.1) are subjected to in-situ coherent compounding, and the two are connectedThe near carrier concentration is easy to generate effective composite effect, thereby effectively scattering phonons, reducing the heat conductivity, simultaneously not blocking the transport of the carriers and being beneficial to the promotion of thermoelectric performance. Meanwhile, Bi in the in-situ coherent composite thermoelectric material1-(a+b)PbaCabThe molar fraction of CuSeO is 5-30%, namely y is more than or equal to 0.05 and less than or equal to 0.3, and the inventor finds that if y is less than 0.05, the main phase of the composite sample is Cu with poor stability2Se, the stability of the obtained sample is poor; and if y is more than 0.3, the carrier concentration of the obtained composite sample is too high, so that the Seebeck coefficient is reduced, the thermal conductivity is improved, and the thermoelectric performance is reduced. Thus, Bi of the present application is used1-(a+b)PbaCabCuSeO mole fraction, and the obtained in-situ coherent composite thermoelectric material has more excellent high-temperature and chemical stability. In conclusion, the in-situ coherent composite thermoelectric material has excellent thermoelectric performance and high stability.
Further, the in-situ coherent composite thermoelectric material (1-y) Cu2+xSe-yBi1-(a+b)PbaCabIn CuSeO, x is more than or equal to 0.01 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.25, a is more than or equal to 0.03 and less than or equal to 0.06, and b is more than or equal to 0.06 and less than or equal to 0.1. Therefore, the comprehensive performance of the in-situ coherent composite thermoelectric material can be further improved.
Further, the in-situ coherent composite thermoelectric material (1-y) Cu2+xSe-yBi1-(a+b)PbaCabIn CuSeO, y is more than or equal to 0.05 and less than or equal to 0.2. Therefore, the average thermoelectric figure of merit of the in-situ coherent composite thermoelectric material can exceed 1.0 in the medium-high temperature region (473K-973K), the material is suitable for the practical application of waste heat power generation or thermoelectric refrigeration in the medium-high temperature region, and the stability of the material is high.
Further, the in-situ coherent composite thermoelectric material (1-y) Cu2+xSe-yBi1-(a+b)PbaCabIn CuSeO, b is 0.06. Thus, Cu2+xSe and Bi1-(a+b)PbaCabCuSeO can achieve the best composite effect, and the stability of the material is higher.
In a second aspect of the invention, the invention provides a method of making the above-described in situ coherent composite thermoelectric material. According to an embodiment of the invention, with reference to fig. 1, the method comprises:
s100: mixing Bi powder and Bi2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder and tabletting
In the step, Bi powder and Bi are mixed2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder, and tabletting to obtain a green body. The inventors have found that by briquetting the starting powders, more intimate contact between the powders is achieved, thereby facilitating the subsequent self-propagating reaction to occur. Preferably, Bi powder and Bi are mixed2O3Before tabletting of the composite powder obtained by mixing the powder, Se powder, Cu powder, PbO powder and CaO powder, grinding the composite powder in an agate mortar for 15-25 min, preferably 20 min. Therefore, the raw material powders can be fully mixed. Specifically, the tabletting process is carried out in a tabletting machine, and the raw material powder is commercially available simple substance powder or oxide powder, and the purity of the raw material powder is over 99.5 percent. Further, the pressure of the tablet is 3 to 6 MPa. The inventor finds that if the pressure of the tabletting is too low, the pressed block is not compact enough, and the subsequent heating reaction is not sufficient; if the pressure of the tablet is too large, the block is easy to break during demoulding. From this, adopt the preforming pressure of this application to be favorable to follow-up self-propagating reaction abundant, and easily the drawing of patterns.
Further, the above Bi powder and Bi2O3The mol ratio of the powder, Se powder, Cu powder, PbO powder and CaO powder is (y (1-a-b)/3): (y (1-a-b)/3): 1: (2+ x-xy-y): ya: yb, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and 0<a≤0.1，0<b is less than or equal to 0.1. The inventor finds that if the value of x is too large, the carrier concentration of the obtained composite sample is too low, and the conductivity is reduced; meanwhile, if the y value is too small, the main phase of the composite sample is Cu with poor stability2Se, the stability of the obtained sample is poor; and if the value of y is too large, the carrier concentration of the obtained composite sample is too high, so that the Seebeck coefficient is reduced, the thermal conductivity is improved, and the thermoelectric performance is reduced. In addition; if the value a is too large, the carrier concentration of the obtained composite sample is too high, so that the Seebeck coefficient is reduced, the thermal conductivity is improved, and the thermoelectric performance is reduced; and if the value of b is too large, a precipitated phase is easily formed, which affects stability. Thereby the device is provided withBy adopting the molar ratio of the application, the prepared in-situ coherent composite thermoelectric material has excellent thermoelectric property and high stability.
S200: heating the green body
In the step, the green body obtained in the step S100 is heated to a certain time, then self-propagating reaction occurs, then the heating is stopped, and natural cooling is waited to obtain (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO in-situ coherent compounded phase-forming samples. It should be noted that the specific manner of heating is not particularly limited, and those skilled in the art can select the heating according to actual needs, for example, the heating may be performed by using an alcohol burner.
Further, the heating temperature is 400-600 ℃, and the time is 1-2 min. The inventors found that if the heating temperature is too low, the self-propagating reaction cannot be initiated; if the heating temperature is too high, Bi and Se are volatile, and meanwhile, if the heating time is too short, the self-propagating reaction cannot be initiated; if the heating time is too long, Bi and Se are easily volatilized and lost into the air. Therefore, the heating condition of the application is favorable for initiating the self-propagating reaction, and meanwhile, the element loss can be avoided.
S300: grinding the phase-forming sample and then carrying out spark plasma sintering
In the step, the in-situ coherent composite thermoelectric material can be obtained by grinding the phase forming sample and then performing spark plasma sintering. The inventor finds that the phase forming sample obtained in the step S200 is a loose block and is difficult to apply in practice, and the compact in-situ coherent composite thermoelectric material can be obtained by grinding the phase forming sample and then performing spark plasma sintering, which is beneficial to the practical application. Specifically, the above-described spark plasma sintering process is performed in a spark plasma sintering furnace.
Furthermore, the sintering temperature is 873-973K, the sintering pressure is 40-50 MPa, and the heat preservation time is 3-5 min. The inventors found that if the sintering temperature is too low, the sample is not dense; and if the sintering temperature is too high, the sample is easy to melt. Meanwhile, if the sintering pressure is too low, the sample is not compact; and if the sintering pressure is too high, the sample is fragile. In addition, if the heat preservation time is too short, the sample is not compact; and if the heat preservation time is too long, crystal grains grow up, and the thermoelectric performance is influenced. Therefore, the sintering conditions of the method are favorable for obtaining the composite material with high density and thermoelectric performance.
The inventors have found that Bi powder and Bi are mixed2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder, tabletting, heating the green compact obtained by tabletting to generate self-propagating reaction to generate (1-y) Cu2+xSe-yBi1-(a+b)PbaCabThe CuSeO in-situ coherent composite phase forming sample is a loose block and is difficult to apply practically, and the compact in-situ coherent composite thermoelectric material can be obtained by grinding the phase forming sample and then carrying out discharge plasma sintering. The raw materials used in the method are the existing commercially available simple substance and oxide raw material powder, the raw materials are easy to obtain, the preparation process is simple, the requirements on experimental equipment and places are low, and the method is favorable for large-scale and industrial production. Meanwhile, the in-situ coherent composite thermoelectric material prepared by the method has excellent thermoelectric performance and high stability.
In a third aspect of the invention, a thermoelectric device is presented. According to an embodiment of the present invention, the thermoelectric device comprises the in-situ coherent composite thermoelectric material described above or the in-situ coherent composite thermoelectric material obtained by the method described above. Therefore, the thermoelectric device has excellent thermoelectric performance and longer service life, and has good application prospects in the aspects of thermoelectric power generation and solid-state refrigeration. It is to be noted that the features and advantages described above with respect to the in-situ coherent composite thermoelectric material and the method of manufacturing the in-situ coherent composite thermoelectric material described above are equally applicable to the thermoelectric device and will not be described herein again.
The following embodiments of the present invention are described in detail, and it should be noted that the following embodiments are exemplary only, and are not to be construed as limiting the present invention. In addition, all reagents used in the following examples are commercially available or can be synthesized according to methods herein or known, and are readily available to those skilled in the art for reaction conditions not listed, if not explicitly stated.
Example 1
(1) Using Bi powder and Bi2O3Powder, Se powder, Cu powder, PbO powder and CaO powder as raw materials, and then according to (1/3y (1-a-b)): (1/3y (1-a-b)): 1: (2+ x-xy-y): ya: a molar ratio of yb (wherein x is 0; y is 30%; a is 3%; b is 6%) 12g of the raw material powder was weighed;
(2) grinding in an agate mortar for 20min, uniformly mixing, taking out the composite powder, putting the composite powder in a metal grinding tool (with the diameter of 12.5mm) and tabletting in a tabletting machine, wherein the pressure is 5MPa, putting the compacted block in an alumina crucible, heating on the outer flame of an alcohol lamp (the temperature is 600 ℃) for about 30s, carrying out self-propagating reaction, removing the alcohol lamp, and waiting for natural cooling;
(3) grinding the cooled loose block until the loose block is uniform and free of large particles, placing the loose block in a graphite mold, and performing spark plasma sintering at 923K under 40MPa for 3min to obtain the in-situ coherent composite thermoelectric material 0.7Cu2Se-0.3Bi0.91Pb0.03Ca0.06CuSeO。
XRD characterization is carried out on the in-situ coherent composite thermoelectric material prepared in example 1, the XRD spectrum of the in-situ coherent composite thermoelectric material refers to figure 2, and the main phase of the in-situ coherent composite thermoelectric material can be found to be Cu2Se phase and BiCuSeO phase. The conductivity of the obtained sample is 316S/cm at 700 ℃, the Seebeck coefficient is 197 mu V/K, and the ZT value can reach more than 1.5; the sample has no obvious change after being tested for 3 times circularly from room temperature to 700 ℃, and the stability of the sample is excellent.
Example 2
(1) Using Bi powder and Bi2O3Powder, Se powder, Cu powder, PbO powder and CaO powder as raw materials, and then according to (1/3y (1-a-b)): (1/3y (1-a-b)): 1: (2+ x-xy-y): ya: a molar ratio of yb (wherein x is 1%; y is 10%; a is 6%; b is 6%) 12g of the raw material powder was weighed;
(2) grinding in an agate mortar for 20min, uniformly mixing, taking out the composite powder, putting the composite powder in a metal grinding tool (with the diameter of 12.5mm) and tabletting in a tabletting machine, wherein the pressure is 5MPa, putting the compacted block in an alumina crucible, heating on the outer flame of an alcohol lamp (the temperature is 600 ℃) for about 30s, carrying out self-propagating reaction, removing the alcohol lamp, and waiting for natural cooling;
(3) grinding the cooled loose block until the loose block is uniform and free of large particles, placing the loose block in a graphite mold, and performing spark plasma sintering at a sintering temperature of 973K and a pressure of 50MPa for 4min to obtain the in-situ coherent composite thermoelectric material of 0.9Cu2.01Se-0.1Bi0.88Pb0.06Ca0.06CuSeO。
XRD characterization is carried out on the in-situ coherent composite thermoelectric material prepared in example 2, and the XRD spectrum refers to figure 3, so that the main phase of the material is Cu2Se phase and BiCuSeO phase. The conductivity of the obtained sample is 253S/cm at 700 ℃, the Seebeck coefficient is 227 mu V/K, and the ZT value can reach more than 2.0; the sample has no obvious change after being tested for 3 times circularly from room temperature to 700 ℃, and the stability of the sample is excellent.
Example 3
(1) Using Bi powder and Bi2O3Powder, Se powder, Cu powder, PbO powder and CaO powder as raw materials, and then according to (1/3y (1-a-b)): (1/3y (1-a-b)): 1: (2+ x-xy-y): ya: a molar ratio of yb (wherein x is 2%; y is 25%; a is 6%; b is 6%) 12g of the raw material powder was weighed;
(2) grinding in an agate mortar for 20min, uniformly mixing, taking out the composite powder, putting the composite powder in a metal grinding tool (with the diameter of 12.5mm) and tabletting in a tabletting machine, wherein the pressure is 5MPa, putting the compacted block in an alumina crucible, heating on the outer flame of an alcohol lamp (the temperature is 600 ℃) for about 30s, carrying out self-propagating reaction, removing the alcohol lamp, and waiting for natural cooling;
(3) grinding the cooled loose block until the loose block is uniform and free of large particles, placing the loose block in a graphite mold, and performing spark plasma sintering at a sintering temperature of 973K and a pressure of 40MPa for 3min to obtain the in-situ coherent composite thermoelectric material of 0.75Cu2.02Se-0.25Bi0.88Pb0.06Ca0.06CuSeO。
The cross section of the in-situ coherent composite thermoelectric material prepared in example 3 was subjected to back-scattered electron microscopyThe SEM image thereof is shown in FIG. 4. The bright part in the picture is Bi0.88Pb0.06Ca0.06CuSeO, with the dark gray fraction being Cu2.02And (5) Se. The conductivity of the obtained sample is 275S/cm at 700 ℃, the Seebeck coefficient is 210 mu V/K, and the ZT value can reach more than 1.8; the sample has no obvious change after being tested for 3 times circularly from room temperature to 700 ℃, and the stability of the sample is excellent.
Example 4
(1) Using Bi powder and Bi2O3Powder, Se powder, Cu powder, PbO powder and CaO powder as raw materials, and then according to (1/3y (1-a-b)): (1/3y (1-a-b)): 1: (2+ x-xy-y): ya: the starting powders were weighed at yb molar ratios (where x ═ 2%; y ═ 5%, 10%, 15%, 20%; a ═ 6%; b ═ 6%) for a total of 4 parts, 12g each, and the samples were designated α, β, γ, and δ;
(2) grinding in an agate mortar for 20min, uniformly mixing, taking out the composite powder, putting the composite powder in a metal grinding tool (with the diameter of 12.5mm) and tabletting in a tabletting machine, wherein the pressure is 5MPa, putting the compacted block in an alumina crucible, heating on the outer flame of an alcohol lamp (the temperature is 600 ℃) for about 30s, carrying out self-propagating reaction, removing the alcohol lamp, and waiting for natural cooling;
(3) grinding the cooled loose block until the loose block is uniform and free of large particles, placing the loose block in a graphite mold, performing spark plasma sintering at a sintering temperature of 973K and a pressure of 40MPa for 3min to obtain the composite thermoelectric material 0.95Cu2.02Se-0.05Bi0.88Pb0.06Ca0.06CuSeO (. alpha.sample), 0.9Cu2.02Se-0.1Bi0.88Pb0.06Ca0.06CuSeO (. beta.sample), 0.85Cu2.02Se-0.15Bi0.88Pb0.06Ca0.06CuSeO (. gamma.sample), 0.8Cu2.02Se-0.2Bi0.88Pb0.06Ca0.06CuSeO (. delta.sample).
Thermoelectric performance tests were performed on 4 samples prepared in example 4, and the ZT values of the α, β, γ, and δ samples at 700 ℃ were all 2.0 or more. Meanwhile, the average ZT values of the four samples over the temperature range of 473K to 973K were calculated. Referring to fig. 5, the average ZT values for the four samples each exceeded 1.2, with the average ZT value for the α sample being about 1.7. All samples have no obvious change after being tested for 3 times at room temperature to 700 ℃ in a circulating way, and the stability is excellent. The in-situ coherent selenium oxide prepared by the method and the components has excellent thermoelectric property in a medium-high temperature region and has the potential of realizing waste heat power generation or thermoelectric refrigeration application in the temperature region.
Comparative example
The difference from example 4 is that: in the step (1), Bi powder and Bi are used2O3Powder, Se powder and Cu powder as raw materials, then according to 1/3 y: 1/3 y: 1: molar ratio of (2-y) (wherein y is 1%) the raw material powder was weighed, and the rest was the same as in example 4. Finally, the thermoelectric material 0.09Cu is prepared2Se-0.01BiCuSeO, the room-temperature conductivity of the material is 342S/cm, the room-temperature Seebeck coefficient is 148 mu V/K, the ZT value is less than 1.0 at 700 ℃, and the thermoelectric property of the material is obviously reduced compared with that of the sample in the embodiment 4; and the glass fiber has slight deformation after being tested for 3 times circularly from room temperature to 700 ℃, and the stability is poor.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer 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, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.

Claims (10)

1. The in-situ coherent composite thermoelectric material is characterized in that the chemical formula of the in-situ coherent composite thermoelectric material is (1-y) Cu2+xSe-yBi1-(a+b)PbaCabCuSeO, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and y is more than or equal to 0<a≤0.1，0<b≤0.1。
2. The in-situ coherent composite thermoelectric material of claim 1, wherein x is 0.01. ltoreq. x.ltoreq.0.02, y is 0.05. ltoreq. y.ltoreq.0.25, a is 0.03. ltoreq. a.ltoreq.0.06, and b is 0.06. ltoreq. b.ltoreq.0.1.
3. The in-situ coherent composite thermoelectric material of claim 2, wherein y is 0.05. ltoreq. y.ltoreq.0.2.
4. A composite thermoelectric material according to any one of claims 1 to 3, wherein b is 0.06.
5. A method of making the in-situ coherent composite thermoelectric material of any one of claims 1 to 4, comprising:
(1) mixing Bi powder and Bi2O3Mixing the powder, Se powder, Cu powder, PbO powder and CaO powder and tabletting to obtain a green body;
(2) heating the green body so as to enable the green body to perform self-propagating reaction to obtain an in-situ coherent composite phase forming sample;
(3) and grinding the phase forming sample, and then performing spark plasma sintering to obtain the in-situ coherent composite thermoelectric material.
6. The method according to claim 5, wherein in step (1), the Bi powder and the Bi2O3The molar ratio of the powder, the Se powder, the Cu powder, the PbO powder and the CaO powder is (y (1-a-b)/3): (y (1-a-b)/3): 1: (2+ x-xy-y): ya: yb, wherein x is more than or equal to 0 and less than or equal to 0.02, y is more than or equal to 0.05 and less than or equal to 0.3, and 0<a≤0.1，0<b≤0.1。
7. The method according to claim 5 or 6, wherein the pressure of the tablet is 3MPa to 6MPa in step (1).
8. The method according to claim 5 or 6, wherein in the step (2), the heating temperature is 400-600 ℃ and the heating time is 1-2 min.
9. The method according to claim 5 or 6, wherein in the step (3), the sintering temperature is 873-973K, the sintering pressure is 40-50 MPa, and the holding time is 3-5 min.
10. A thermoelectric device comprising the in-situ coherent composite thermoelectric material according to any one of claims 1 to 4 or the in-situ coherent composite thermoelectric material obtained by the method according to any one of claims 5 to 9.
CN202111530297.9A 2021-12-14 2021-12-14 In-situ coherent composite thermoelectric material and preparation method and application thereof Pending CN114203893A (en)

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