CN113421959B - N-type bismuth telluride-based room temperature thermoelectric material and preparation method thereof - Google Patents
N-type bismuth telluride-based room temperature thermoelectric material and preparation method thereof Download PDFInfo
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- CN113421959B CN113421959B CN202110692841.3A CN202110692841A CN113421959B CN 113421959 B CN113421959 B CN 113421959B CN 202110692841 A CN202110692841 A CN 202110692841A CN 113421959 B CN113421959 B CN 113421959B
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
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- H10N10/851—Thermoelectric active materials comprising inorganic compositions
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Abstract
The invention discloses an n-type bismuth telluride-based room temperature heatThe chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 2‑x Sb x Te 3 Wherein x =0-1.3. The n-type Bi 2‑x Sb x Te 3 The thermoelectric material has better thermoelectric figure of merit near room temperature due to the n-type Bi 2‑x Sb x Te 3 And p-type Bi 2‑x Sb x Te 3 The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged. The preparation method provided by the invention is simple, low in cost and good in repeatability.
Description
Technical Field
The invention relates to the field of thermoelectric materials, in particular to an n-type bismuth telluride-based room-temperature thermoelectric material and a preparation method thereof.
Background
The global energy consumption is huge, the utilization efficiency of the existing energy is low, most of the energy is wasted in the form of waste heat, and the thermoelectric material is widely concerned as a new energy material capable of directly converting heat energy into electric energy.
The thermoelectric material is a material which realizes the mutual conversion of electric energy and heat energy by utilizing three thermoelectric effects. The thermoelectric device is formed by thermally connecting p-type and n-type thermocouple pairs in parallel and electrically connecting the p-type and n-type thermocouple pairs in series. Bismuth telluride is the first thermoelectric material found in the thermoelectric field and has been the only commercial application at present for the longest time. P-type Bi 2-x Sb x Te 3 And n-type Bi 2 Te 3-x Se x Is the basis of the application of the thermoelectric device, and the working efficiency of the thermoelectric device mainly depends on the thermoelectric figure of merit zT, zT = (S) of the thermoelectric material 2 σ/κ) T, where S, σ and κ are the Seebeck coefficient, electrical conductivity and thermal conductivity (including carrier thermal conductivity κ), respectively e And lattice thermal conductivity κ l ) And T is the service temperature of the device.
In commercial application, the thermoelectric material can be used for thermoelectric power generation and room temperature solid state refrigeration, but the thermoelectric power generation efficiency is low, and the room temperature solid state refrigeration has wide application prospect. At present, p-type Bi 2-x Sb x Te 3 zT value of 1.4-1.8, and n-type Bi 2 Te 3-x Se x The zT of the p-type thermoelectric material is 0.8-1.4, the performance of the p-type thermoelectric material and the performance of the n-type thermoelectric material are different, the thermoelectric peak value of the p-type thermoelectric material can be obtained at medium and low temperature, the thermoelectric peak value of the n-type thermoelectric material can be almost obtained only at medium and high temperature, the application temperature zones of the p-type thermoelectric material and the n-type thermoelectric material are not matched, and the service life and the yield of devices are low when the p-type thermoelectric material and the n-type thermoelectric material are used for room-temperature solid-state refrigeration.
Therefore, it is of great significance to develop an n-type bismuth telluride-based thermoelectric material with a better thermoelectric figure of merit near room temperature.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide an n-type bismuth telluride-based room temperature thermoelectric material and a preparation method thereof, aiming at solving the problems that the application temperature regions of the existing p-type thermoelectric material and the existing n-type thermoelectric material are not matched, and the service life and the yield of devices are low when the n-type bismuth telluride-based room temperature thermoelectric material is used for room temperature solid state refrigeration.
The technical scheme of the invention is as follows:
in a first aspect of the present invention, an n-type bismuth telluride-based room-temperature thermoelectric material is provided, wherein the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material is Bi 2-x Sb x Te 3 Wherein x =0-1.3.
Optionally, the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 1.5 Sb 0.5 Te 3 Or Bi 1.4 Sb 0.6 Te 3 。
In a second aspect of the present invention, there is provided a method for preparing an n-type bismuth telluride-based room temperature thermoelectric material, comprising the steps of:
according to the chemical formula Bi 2-x Sb x Te 3 Weighing Bi metal blocks, sb metal blocks and Te metal blocks according to the stoichiometric ratio of the elementsSmelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot block;
ball-milling the alloy ingot to obtain alloy powder;
and sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material.
Optionally, the specific steps of smelting the Bi metal block, the Sb metal block, and the Te metal block include:
putting the Bi metal block, the Sb metal block and the Te metal block into a smelting furnace, heating to 600-700 ℃ at a heating rate of 2-4 ℃/min, and preserving heat for 2-4h;
then heating to 900-1000 ℃ at the heating rate of 2-4 ℃/min, and preserving the heat for 10-20h.
Optionally, the Bi metal blocks, the Sb metal blocks and the Te metal blocks are put into a smelting furnace in the order of melting point from high to low.
Optionally, the specific step of ball milling the alloy ingot comprises:
and putting the alloy ingot into a ball milling tank, adding steel balls with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.
Optionally, steel balls with diameters of 15mm, 12mm, 7mm and 5mm are added.
Optionally, the number ratio of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1.
Optionally, the specific step of sintering the alloy powder includes:
placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;
placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.
Optionally, the diameter of the first graphite mold is 10-20mm, and the diameter of the second graphite mold is 12.7-25mm.
Has the beneficial effects that: the invention providesAn n-type bismuth telluride-based room-temperature thermoelectric material and a preparation method thereof, wherein the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material is Bi 2-x Sb x Te 3 It has a better thermoelectric figure of merit at around room temperature due to n-type Bi 2-x Sb x Te 3 And p-type Bi 2-x Sb x Te 3 The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged.
Drawings
FIG. 1 shows n-type Bi in example 1 of the present invention 2-x Sb x Te 3 The Seebeck coefficient test result chart.
FIG. 2 shows n-type Bi in example 2 of the present invention 1.5 Sb 0.5 Te 3 The zT values of (a) are shown in the test results.
FIG. 3 shows n-type Bi in example 2 of the present invention 1.5 Sb 0.5 Te 3 Graph of zT values test results when performing repeatable tests.
FIG. 4 shows n-type Bi in example 2 of the present invention 1.5 Sb 0.5 Te 3 The expansion coefficient test result of (2).
FIG. 5 shows n-type Bi in example 2 of the present invention 1.5 Sb 0.5 Te 3 The results of the compression and bending tests.
Detailed Description
The invention provides an n-type bismuth telluride-based room temperature thermoelectric material and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The embodiment of the invention provides an n-type bismuth telluride-based room temperature thermoelectric material, wherein the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 2-x Sb x Te 3 Wherein x =0-1.3.
In the field of bismuth telluride, p-type Bi 2-x Sb x Te 3 N-type Bi 2 Te 3-x Se x The method is almost a custom cognition, the thermoelectric peak value of the p-type bismuth telluride-based thermoelectric material can be obtained at a medium-low temperature, the thermoelectric peak value of the n-type bismuth telluride-based thermoelectric material can be obtained at a medium-high temperature, and when the bismuth telluride device is used for room-temperature solid-state refrigeration, the application temperature regions of the p-type bismuth telluride-based thermoelectric material and the n-type bismuth telluride-based thermoelectric material are not matched, so that the efficiency of the device is low. Therefore, the method is particularly important for developing the high-performance n-type bismuth telluride-based thermoelectric material near room temperature, and no researchers are available to prepare the high-performance n-type Bi near room temperature 2-x Sb x Te 3 The invention relates to a thermoelectric material, in particular to an n-type bismuth telluride-based room-temperature thermoelectric material, namely n-type Bi, prepared by a simple preparation method 2-x Sb x Te 3 Wherein x =0-1.3, from p-type Bi 2-x Sb x Te 3 Thermoelectric material to n-type Bi 2- x Sb x Te 3 Transformation of thermoelectric material, and the n-type Bi 2-x Sb x Te 3 Has good thermoelectric property near room temperature, the zT value near room temperature is larger than that of most n-type thermoelectric materials, n-type Bi 2-x Sb x Te 3 With the prior art p-type Bi 2-x Sb x Te 3 The two elements are composed of the same element, so that the two elements are more matched in mechanical thermodynamics, and the service life and the yield of the thermoelectric device can be greatly improved.
In one embodiment, the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 1.5 Sb 0.5 Te 3 Or Bi 1.4 Sb 0.6 Te 3 。
The embodiment of the invention also provides a preparation method of the n-type bismuth telluride-based room-temperature thermoelectric material, which comprises the following steps:
s1, according to the chemical formula Bi 2-x Sb x Te 3 Weighing a Bi metal block, an Sb metal block and a Te metal block according to the stoichiometric ratio of the elements, smelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot;
s2, performing ball milling on the alloy ingot to obtain alloy powder;
s3, sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material.
In this embodiment, the Bi metal block to be weighed is composed of a plurality of small metal blocks, and similarly, the Sb metal block and the Te metal block to be weighed are also composed of a plurality of small metal blocks. Of course, if the mass of the prepared n-type bismuth telluride-based room temperature thermoelectric material is small, there is a case where there is only one Bi metal block or Sb metal block or Te metal block, that is, the present embodiment does not limit the block size of the Bi metal block, sb metal block or Te metal block.
In the prior art, an n-type bismuth telluride-based thermoelectric material Bi 2 Te 3-x Se x The boiling point and the evaporation energy of the element Se are far lower than those of the element Te, the Se is extremely easy to volatilize in the smelting process, so that the V-group element is excessive and deviates from the normal atomic ratio, and the Se content is changed by adopting different equipment or different experimenters, so that the repeatability is extremely low (the repeatability is poor, n-type Bi is adopted 2 Te 3-x Se x The pain point which is difficult to solve in the preparation process) does not meet the requirement of industrial production. And if it is desired to obtain high-performance n-type Bi 2 Te 3-x Se x The preparation method is complex and the cost is high. Compared with the prior art, the n-type Bi in the embodiment 2- x Sb x Te 3 The method does not contain Se, does not have the problem of Se volatilization in the prior art, has good repeatability, adopts a technical route of smelting, ball milling and sintering in the embodiment, and has simple preparation method and low cost.
In the ball milling process, according to the formation rule of the inversion defects, after Sb is added, the number of the inversion defects can be increased, and donor-like effect can occur, so that Bi 2-x Sb x Te 3 The conductive material has n-type conductivity, but the Sb content is increased continuously, the number of the inversion defects is more than required, and the generated vacancies can be compounded with electrons, so that the carrier concentration is reduced to be within an optimal range. And Bi 2-x Sb x Te 3 Has an energy band degeneracy higher than Bi 2 Te 3-x Se x The degeneracy of the energy band is improvedThe effect of the aspect is favorable for n-type Bi 2-x Sb x Te 3 Good electrical properties are obtained. An increase in Sb content only slightly reduces the forbidden bandwidth, which is beneficial to keep the zT peak at room temperature. In addition, the sintering process involves thermal deformation, and phonons with different frequencies are scattered by alloy scattering and different defects generated by the thermal deformation, so that the lattice thermal conductivity is reduced, and a higher zT value is obtained. The point defect model of the donor-like effect is shown in the following formula (1), wherein,
and
is Bi and Te vacancies produced during thermal deformation, bi' Te The crystal growth process generates inversion defects, the interaction of vacancies generated in the thermal deformation process and the inversion defects generated in the crystal growth process generates additional electrons e', the generated additional electrons continuously exist in the thermal deformation process, and the electron concentration is increased. Thus, the donor-like effect during ball milling and hot deformation increases n-type Bi 2-x Sb x Te 3 Electrical properties of (2).
In step S1, bi is expressed by the chemical formula 2-x Sb x Te 3 The Bi metal block, the Sb metal block, and the Te metal block are weighed according to the stoichiometric ratio of the respective elements, and when x =1, the Bi metal block, the Sb metal block, and the Te metal block are weighed according to the molar ratio of 1.
In one embodiment, the specific steps of melting the Bi metal block, the Sb metal block, and the Te metal block include:
putting the Bi metal block, the Sb metal block and the Te metal block into a smelting furnace, heating to 600-700 ℃ at a heating rate of 2-4 ℃/min, and preserving heat for 2-4h;
then the temperature is raised to 900-1000 ℃ at the temperature raising speed of 2-4 ℃/min, and the temperature is preserved for 10-20h.
Keeping the temperature for 2-4h at 600-700 ℃, wherein the three metal blocks are melted, then raising the temperature to 900-1000 ℃ at the temperature raising speed of 2-4 ℃/min, and keeping the temperature for 10-20h, namely keeping the temperature for a long time at high temperature so as to ensure that the melted metal blocks are uniformly mixed to form solid solution and no second phase is generated.
In one embodiment, the Bi metal blocks, sb metal blocks, and Te metal blocks are put into a smelting furnace in order from high melting point to low melting point. Since the melting point of Sb is higher than that of Te and higher than that of Bi, in this embodiment, the Sb metal block is first put into a melting furnace, the Te metal block is then put into the melting furnace, and finally the Bi metal block is put into the melting furnace.
In one embodiment, the Sb metal block is put into a quartz tube, the Te metal block is put into the quartz tube, the Bi metal block is put into the quartz tube, the quartz tube is vacuumized and sealed by hydrogen flame, and then the vertical (the Sb metal block, the Te metal and the Bi metal block are arranged in sequence from bottom to top of the quartz tube) is put into a resistance furnace for smelting.
In step S2, in one embodiment, the step of ball-milling the alloy ingot includes:
and putting the alloy ingot into a ball milling tank, adding a steel ball with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.
In one embodiment, steel balls with diameters of 15mm, 12mm, 7mm, 5mm are added.
In this step, steel balls with diameters of 15mm, 12mm, 7mm and 5mm are required to be added simultaneously, the steel balls with diameters of 15mm and 12mm are helpful for crushing alloy ingots, and the steel balls with diameters of 7mm and 5mm are helpful for grinding fine powder, so that alloy powder is obtained. The ball milling time is not suitable to be too long or too short, the too long affects the vacancy number generated in the n-type bismuth telluride material, the carrier concentration is finally affected, and the too short powder is not fine enough.
In one embodiment, the number ratio of steel balls with diameters of 15mm, 12mm, 7mm, 5mm is 1.
In one embodiment, the number of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1, 3, 10 and 22 respectively. In specific implementation, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm are added into a ball milling tank to ball mill the alloy ingot.
In one embodiment, the ball mill pot is selected from one of a stainless steel ball mill pot and an agate ball mill pot, but is not limited thereto.
In one embodiment, after the ball milling of the alloy ingot to obtain the alloy powder, the method further comprises: sieving with a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns.
In step S3, in one embodiment, the step of sintering the alloy powder includes:
placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;
placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.
In the embodiment, the sintering temperature and pressure are not suitable to be too low, the temperature is too low, the donor-like effect in the n-type bismuth telluride material is not strong enough, the carrier concentration is difficult to optimize, the performance is low, the temperature is close to the melting point of the bismuth telluride solid solution at 500 ℃, the improvement of the thermoelectric performance is most beneficial, the n-type bismuth telluride-based room-temperature thermoelectric material sintered at too low pressure is not compact, the mechanical performance is poor, the n-type bismuth telluride-based room-temperature thermoelectric material sintered at too high pressure is too compact, the thermal conductivity is increased due to the improvement of the density, and the improvement of the thermoelectric figure of merit is not beneficial.
In this embodiment, the diameter of the first graphite mold is smaller than the diameter of the second graphite mold, and thermal deformation can be achieved. The thermal deformation is favorable for enhancing the texture of the n-type bismuth telluride-based room-temperature thermoelectric material, improving the mobility and improving the electrical property, particularly because of the layered structure and weak-Te of the bismuth telluride 1 -Te 1 -bond toThe bismuth telluride based thermoelectric material can easily slide along a basal plane vertical to the c axis of the crystal to form a strong texture, the bismuth telluride based thermoelectric material can be continuously extruded in the thermal deformation process, the texture is easy to generate, and the texture is favorable for electron transportation and improves the electron mobility. In addition, the defects of multiple scales are introduced into the n-type bismuth telluride-based room temperature thermoelectric material through thermal deformation, a multi-scale scattering center is formed, phonons of different frequencies are scattered, the lattice thermal conductivity is reduced, the thermoelectric performance is improved, the strong donor-like effect of the n-type bismuth telluride-based room temperature thermoelectric material can be improved through the thermal deformation, and the carrier concentration is improved.
In specific implementation, the alloy powder is placed in a first graphite die and then is placed in a plasma discharge sintering furnace to be sintered for 5min at 500 ℃ and 40-50 MPa; and taking out the block after sintering, cleaning the surface of the block, removing the graphite paper, putting the block into a second graphite mold with the diameter larger than that of the first graphite mold, and then putting the block into a plasma discharge sintering furnace to be sintered for 5min at the temperature of 500 ℃ and the pressure of 40-50MPa, thereby realizing the thermal deformation process.
In one embodiment, the first graphite mold has a diameter of 10 to 20mm, and the second graphite mold has a diameter of 12.7 to 25mm.
In specific implementation, a first graphite mold with the diameter of 10mm and a second graphite mold with the diameter of 12.7mm can be selected to realize the thermal deformation process; or a first graphite die with the diameter of 12.7mm and a second graphite die with the diameter of 15mm can be selected to realize the thermal deformation process; the thermal deformation process can also be realized by selecting a first graphite mold with the diameter of 15mm and a second graphite mold with the diameter of 20 mm; the thermal deformation process can also be realized by selecting a first graphite mold with the diameter of 20mm and a second graphite mold with the diameter of 25mm.
The invention is further illustrated by the following specific examples.
Example 1
n-type Bi 2-x Sb x Te 3 Preparation of room temperature thermoelectric materials
According to the chemical formula Bi 2-x Sb x Te 3 The stoichiometric ratio of the elements in the formula (2-x): x:3 (which isWherein x is 0, 0.1, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3) and weighing Bi metal blocks, sb metal blocks and Te metal blocks with corresponding mass. Then putting the Sb metal block into a quartz tube, putting the Te metal block into the quartz tube, finally putting the Bi metal block into the quartz tube, vacuumizing, sealing by using hydrogen flame, then vertically putting the vertical (the Sb metal block, the Te metal and the Bi metal block are sequentially arranged from bottom to top of the quartz tube) into a high-temperature box-type resistance furnace, gradually increasing the temperature from room temperature to 650 ℃ at the temperature rise speed of 2 ℃/min, preserving heat for 2h, then increasing the temperature to 900 ℃ at the temperature rise speed of 4 ℃/min, preserving heat for 10h, and cooling to obtain the alloy ingot block. Then adding the alloy ingot, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm into a stainless steel ball milling tank, ball milling for 20min at the rotating speed of 1200r/min, and sieving by using a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns. Placing the alloy powder in a graphite die with the diameter of 15mm, and then sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50 MPa; taking out the block after sintering, cleaning the surface of the block, removing graphite paper, putting the block into a graphite mold with the diameter of 20mm, and sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50MPa to obtain the n-type Bi 2-x Sb x Te 3 Thermoelectric material, wherein x is 0, 0.1, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3. For Bi 2-x Sb x Te 3 The thermoelectric material is subjected to Seebeck coefficient (seebeck coefficient) test, the results are shown in figure 1, the Seebeck coefficients of all samples are negative numbers, and the Bi prepared by the method is proved 2-x Sb x Te 3 The thermoelectric material is n-type.
Example 2
n-type Bi 1.5 Sb 0.5 Te 3 Preparation of room temperature thermoelectric materials
According to the chemical formula Bi 2-x Sb x Te 3 The stoichiometric ratio of each element in the formula (I) is 1.5:0.5:3, weighing Bi metal blocks, sb metal blocks and Te metal blocks with corresponding mass. Then placing Sb metal block into quartz tube, and then placing Te goldThe metal block is put into a quartz tube, finally a Bi metal block is put into the quartz tube, the quartz tube is vacuumized and sealed by hydrogen flame, then the metal block is vertically put into a high-temperature box type resistance furnace (the quartz tube is sequentially provided with a Sb metal block, a Te metal and a Bi metal block from bottom to top), the temperature is gradually increased from room temperature to 650 ℃ at the temperature rising speed of 2 ℃/min, the temperature is kept for 2h, then the temperature is increased to 900 ℃ at the temperature rising speed of 4 ℃/min, the temperature is kept for 10h, and the alloy ingot block is obtained after cooling. Then adding the alloy ingot, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm into a stainless steel ball milling tank, ball milling for 20min at the rotating speed of 1200r/min, and sieving by using a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns. Placing the alloy powder in a graphite die with the diameter of 15mm, and sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50 MPa; taking out the block after sintering, cleaning the surface of the block, removing graphite paper, putting the block into a graphite mold with the diameter of 20mm, and sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50MPa to obtain n-type Bi 1.5 Sb 0.5 Te 3 A room temperature thermoelectric material.
Testing the zT value:
for n-type Bi in example 2 1.5 Sb 0.5 Te 3 The result of the zT value test of the thermoelectric material is shown in fig. 2, where HD represents the thermal deformation and it can be seen that n-type Bi is around 330K 1.5 Sb 0.5 Te 3 The room temperature performance of the thermoelectric material is higher than that of most n-type thermoelectric materials, but is slightly lower than that of Bi doped or subjected to multiple thermal deformation or other more complex processes 2 Te 3- x Se x From this, it is known that n-type Bi 1.5 Sb 0.5 Te 3 The room temperature thermoelectric material has a better thermoelectric figure of merit near room temperature.
And (3) repeatability testing:
the preparation steps of example 2 are repeated for 4 times, and the obtained 4 samples are subjected to a zT value test, the results of which are shown in fig. 3, the highest performance of all the samples is 330-350K, and the original performance can be maintained after multiple times of preparation and multiple tests.
And p-type Bi 1.5 Sb 0.5 Te 3 The matching test of (2):
for n-type Bi in example 2 1.5 Sb 0.5 Te 3 P-type Bi in the prior art 1.5 Sb 0.5 Te 3 And n-type Bi 2 Te 2.7 Se 0.3 The results of the expansion coefficient test are shown in FIG. 4. As can be seen from FIG. 4, the n-type Bi in example 1 is not lower than 300K and not lower than 360K at low temperature 1.5 Sb 0.5 Te 3 Are all than n type Bi 2 Te 2.7 Se 0.3 Is more matched with p-type Bi 1.5 Sb 0.5 Te 3 。
For n-type Bi in example 2 1.5 Sb 0.5 Te 3 P-type Bi in the prior art 1.5 Sb 0.5 Te 3 And n-type Bi 2 Te 2.7 Se 0.3 The results of the compression and bending resistance tests are shown in FIG. 5. As can be seen from FIG. 5, n-type Bi in example 2 1.5 Sb 0.5 Te 3 Higher compression resistance than p-type Bi 1.5 Sb 0.5 Te 3 And n-type Bi 2 Te 2.7 Se 0.3 Bending resistance of the material is also equal to that of p-type Bi 1.5 Sb 0.5 Te is more matched.
In summary, the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material and the preparation method thereof provided by the invention is Bi 2-x Sb x Te 3 Where x =0-1.3, which has a better thermoelectric figure of merit around room temperature due to n-type Bi 2-x Sb x Te 3 And p-type Bi 2-x Sb x Te 3 The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged. The preparation method provided by the invention is simple, low in cost and good in repeatability.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.
Claims (7)
1. A preparation method of an n-type bismuth telluride-based room temperature thermoelectric material is characterized by comprising the following steps:
according to the chemical formula Bi 2-x Sb x Te 3 Weighing a Bi metal block, an Sb metal block and a Te metal block according to the stoichiometric ratio of the elements, smelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot;
ball-milling the alloy ingot to obtain alloy powder;
sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material;
the specific steps of smelting the Bi metal block, the Sb metal block and the Te metal block comprise:
putting the Bi metal block, the Sb metal block and the Te metal block into a smelting furnace, heating to 600-700 ℃ at a heating rate of 2-4 ℃/min, and preserving heat for 2-4h;
then heating to 900-1000 ℃ at the heating rate of 2-4 ℃/min, and preserving heat for 10-20h;
putting the Bi metal block, the Sb metal block and the Te metal block into a smelting furnace in the sequence of high melting point to low melting point;
the specific steps of ball milling the alloy ingot comprise:
and putting the alloy ingot into a ball milling tank, adding steel balls with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.
2. The method according to claim 1, wherein steel balls having diameters of 15mm, 12mm, 7mm, and 5mm are added.
3. The method for preparing the steel ball according to claim 2, wherein the number ratio of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1.
4. The method according to claim 1, wherein the step of sintering the alloy powder comprises:
placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;
placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.
5. The method of claim 4, wherein the first graphite mold has a diameter of 10 to 20mm, and the second graphite mold has a diameter of 12.7 to 25mm.
6. An n-type bismuth telluride-based room-temperature thermoelectric material characterized by being prepared by the preparation method of any one of claims 1 to 5.
7. The n-type bismuth telluride-based room temperature thermoelectric material as defined in claim 6, wherein the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 1.5 Sb 0.5 Te 3 Or Bi 1.4 Sb 0.6 Te 3 。
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