阅读说明：本技术 产生类施主效应的碲化铋基热电材料的回收再处理方法 (Recovery and reprocessing method of bismuth telluride-based thermoelectric material generating donor-like effect ) 是由 苏贤礼 陶奇睿 唐新峰 李强 张政楷 于 2021-07-21 设计创作，主要内容包括：本发明公开了一种产生类施主效应的碲化铋基热电材料的回收再处理方法,将产生类施主效应的多晶粉末碲化铋基材料通过区熔法制备碲化铋基热电材料块体,从而得到消除类施主效应的碲化铋基热电材料,从而实现已经产生类施主效应的碲化铋基热电材料的回收再处理。本发明提出了回收再处理已产生类施主效应的碲化铋基热电材料的解决方案,有助于碲化铋基热电材料的大规模商业化应用。(The invention discloses a method for recycling and reprocessing a bismuth telluride-based thermoelectric material generating a donor-like effect, which is characterized in that a polycrystalline powder bismuth telluride-based material generating the donor-like effect is used for preparing a bismuth telluride-based thermoelectric material block by a zone melting method, so that the bismuth telluride-based thermoelectric material eliminating the donor-like effect is obtained, and the recycling and reprocessing of the bismuth telluride-based thermoelectric material generating the donor-like effect is realized. The invention provides a solution for recycling and reprocessing the bismuth telluride-based thermoelectric material which generates the donor-like effect, and is beneficial to large-scale commercial application of the bismuth telluride-based thermoelectric material.)

1. The method for recovering and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect is characterized in that polycrystalline powder bismuth telluride-based material generating the donor-like effect is used for preparing a high-orientation bismuth telluride-based single crystal material through a zone melting method, namely the bismuth telluride-based thermoelectric material eliminating the donor-like effect, so that the recovery and reprocessing of the bismuth telluride-based thermoelectric material generating the donor-like effect are realized.

2. The method of claim 1, wherein the bismuth telluride-based thermoelectric material has a chemical formula of Bi_2-ySb_yTe_3-xSe_x，0≤ x ≤ 1，0 ≤ y≤ 2。

3. The method for recycling and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect according to claim 1, wherein the method comprises the following steps:

(1) the bismuth telluride-based thermoelectric material raw material which generates the donor-like effect is transferred to a quartz tube for vacuum sealing and is melted in a muffle furnace to obtain Bi_2-ySb_yTe_3-xSe_xA bulk material; wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 2;

(2) adding Bi_2-ySb_yTe_3-xSe_xAnd putting the block material into a zone melting furnace, and growing to obtain the high-orientation bismuth telluride-based single crystal material.

4. The method as claimed in claim 3, wherein the melting temperature is 923-.

5. The method as claimed in claim 3, wherein the zone melting temperature is 873-1173K, and the zone melting pulling speed is 3.6-180mm h^-1。

Technical Field

The invention belongs to the technical field of inorganic functional materials, and particularly relates to a recovery and reprocessing method of a bismuth telluride-based thermoelectric material generating donor-like effect.

Background

Bismuth telluride-based thermoelectric materials are by far the only thermoelectric materials commercially available. The preparation method which is researched more and has excellent performance is advantageousPreparation of polycrystalline Bi by powder metallurgy₂Te₃The base compound is combined with structural nanocrystallization, so that the excellent electric transport performance of a sample is kept, the grain boundary scattering is increased, the lattice thermal conductivity is reduced, and the ZT value is greatly improved. In addition, the mechanical properties of the sample are optimized due to the grain refinement and the nano composite phase, and compared with a ZM sample, the mechanical properties of the SPS sintered sample can be improved by 6-7 times. A great deal of research work proves that the method is used for p-type Bi₂Te₃The base compounds are clearly very successful, with ZT values up to 1.96. However, this approach is for n-type Bi₂Te₃For the base compound, the ZT value is still difficult to be greatly improved. Polycrystalline n-type Bi prepared by powder metallurgy₂Te₃After the grains are refined, the grain boundary scattering is enhanced, and the randomly oriented grains in the material cause the reduction of the orientation of the material, so that the mobility is sharply reduced, and the electric transport performance of the material is remarkably deteriorated.

Furthermore, CN112670399A Bi₂Te₃The method for eliminating donor-like effect of base thermoelectric material discloses that the donor-like effect generated in the ingot crushing process can make the carrier concentration of base body be uncontrollable, irreversibly and violently increased, so that the Fermi level can be stabilized in the conduction band, and basically does not change along with the change of base body component (doping, solid solution or compounding), and its performance can be sharply deteriorated. The corresponding disclosed means for eliminating donor-like effect is to utilize the elimination of donor-like effect to generate the required precursor defect, thereby achieving the effect of suppressing donor-like effect before the donor-like effect is not generated, but does not mention how to eliminate donor-like effect for the sample generating donor-like effect.

Due to the generation of the donor-like effect, the electron carrier concentration in the material can be obviously improved, so that the carrier concentration deviates from an optimal interval, and the thermoelectric performance is seriously degraded. However, there is no good solution for eliminating the donor-like effect in the sample which has generated the donor-like effect and recovering the carrier concentration of the substrate to the normal value. Therefore, how to eliminate the donor-like effect in the sample which generates the donor-like effect and turn waste into wealth has very important significance for further large-scale commercial application of the bismuth telluride-based thermoelectric material.

Disclosure of Invention

Aiming at the donor-like effect in the existing bismuth telluride-based thermoelectric material, the method for recycling and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect is provided, the donor-like effect of the material is eliminated, the carrier concentration is in the optimal carrier concentration interval of the bismuth telluride-based thermoelectric material, the dimensionless thermoelectric figure of merit (ZT) is also optimized, and the method is beneficial to large-scale commercial application of the bismuth telluride-based thermoelectric material.

The technical scheme adopted by the invention for solving the problems is as follows:

the method for recovering and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect is characterized in that polycrystalline powder bismuth telluride-based material generating the donor-like effect is used for preparing a high-orientation bismuth telluride-based single crystal material through a zone melting method, namely the bismuth telluride-based thermoelectric material eliminating the donor-like effect is obtained, and thus the recovery and reprocessing of the bismuth telluride-based thermoelectric material generating the donor-like effect are realized.

According to the scheme, the chemical general formulas of the polycrystalline powder bismuth telluride-based thermoelectric material and the bismuth telluride-based thermoelectric material block are Bi_2-ySb_yTe_3-xSe_x，0≤x≤1，0≤y≤2。

The invention relates to a recovery and reprocessing method of a bismuth telluride-based thermoelectric material generating donor-like effect, which comprises the following steps:

(1) the bismuth telluride-based thermoelectric material raw material which generates the donor-like effect is transferred to a quartz tube for vacuum sealing and is melted in a muffle furnace to obtain Bi_2-ySb_yTe_3-xSe_xA bulk material; wherein x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 2;

(2) adding Bi_2-ySb_yTe_3-xSe_xAnd placing the block material into a zone melting furnace, slowly pulling, and growing to obtain the high-orientation bismuth telluride-based single crystal material with the donor-like effect eliminated.

According to the scheme, when the bismuth telluride-based thermoelectric material block is prepared by the zone melting method, the melting temperature is 923-5-24 h; the zone melting temperature is 873-^-1. The zone-melting pulling speed is preferably 5-15mm h^-1。

Since the donor-like effect is more remarkable in the n-type bismuth telluride-based thermoelectric material, the n-type bismuth telluride-based thermoelectric material is selected as the base material in the embodiment. According to the method for recycling and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect, the generated donor-like effect of the bismuth telluride-based thermoelectric material obtained by the method is eliminated, and the highest conductivity of the bismuth telluride-based thermoelectric material at 300K is 9-11 multiplied by 10⁴Sm^-1Simultaneously obtain-195 to-225 mu V K^-1Seebeck coefficient and highest power factor PF_max4.1-4.7 mW m^-1K^-2Finally, the ZT can be 0.90-1.05 at 300K; and the maximum ZT is obtained at 323-373K_max0.95 to 1.15.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides an effective means for recovering and reprocessing the bismuth telluride-based thermoelectric material which generates the donor-like effect, thereby eliminating the generated donor-like effect and being beneficial to the recovery of the carrier concentration in the material to an optimal interval. Compared with a sample generating the donor-like effect, the sample with the donor-like effect eliminated has the carrier concentration remarkably reduced and is in the optimal carrier concentration interval of the bismuth telluride-based thermoelectric material; meanwhile, the absolute value and the power factor of the Seebeck coefficient are both obviously improved, the total thermal conductivity is obviously reduced, and finally the dimensionless thermoelectric figure of merit ZT is also optimized. The invention provides an effective means for recovering and reprocessing the bismuth telluride-based thermoelectric material which generates the donor-like effect, and is beneficial to further large-scale production of the bismuth telluride-based thermoelectric material.

Drawings

FIG. 1 is a graph of conductivity versus temperature for the samples of example 1 and comparative examples 1, 2;

FIG. 2 is a graph of the Seebeck coefficient as a function of temperature for the samples of example 1 and comparative examples 1, 2;

FIG. 3 is a graph of power factor versus temperature for the samples of example 1 and comparative examples 1, 2;

FIG. 4 is a graph of total thermal conductivity as a function of temperature for the samples of example 1 and comparative examples 1, 2;

FIG. 5 is a plot of ZT values versus temperature for the samples of example 1 and comparative examples 1, 2;

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

In the following examples and comparative examples, the samples were cut and then sanded and polished with 400-2000 mesh sandpaper; wherein a cuboid sample with the diameter of 3 multiplied by 12mm is cut out along the growth direction of the zone-melting sample by utilizing the linear cutting, a wafer with the diameter of 6mm is cut out along the growth direction of the zone-melting sample by utilizing the linear cutting, the wafer is respectively placed in an ZEM-3 type thermoelectric performance testing device, the electric conductivity and the Seebeck coefficient in 300-523K are tested in the He atmosphere, and the thermal diffusion coefficient in 300-523K is tested in the LFA-457 laser thermal conductivity instrument in the Ar atmosphere.

In the following examples and comparative examples, both the electrical conductivity and the Seebeck coefficient were measured in a He atmosphere by the standard four-probe method on a thermoelectric property testing apparatus model ZEM-3 manufactured by Japan vacuum engineering, and the test temperature range was 298-.

In the following examples and comparative examples, the thermal conductivity was measured by measuring the heat capacity C of the sample_pThree parameters of thermal diffusion coefficient D and density rho are calculated, namely thermal conductivity kappa is equal to C_pD rho; wherein a Laser Flash method is adopted to measure the thermal diffusion coefficient D of the sample, and the adopted instrument is a Netzsch LFA-457 Laser thermal conductivity instrument produced by Germany Chi Nachi company; heat capacity (C)_p) Obtained by Differential thermal analysis (DSC) (TA DSC Q20); the density ρ is measured by the archimedes method.

Power factor PF ═ S²Alpha, dimensionless thermoelectric figure of merit ZT ═ S²Alpha T/kappa, S is Seebeck coefficient of the material, alpha is conductivity, T is absolute temperature, and kappa is heatAnd (4) conductivity.

In the following examples, the raw material used was a commercial float zone block (Bi)₂Te_2.79Se_0.21) Specific room temperature electrothermal transfer properties are shown in table 1.

TABLE 1 Room temperature electrothermal transfer Performance of commercial zone-melting blocks

Example 1

The method for recycling and reprocessing the bismuth telluride-based thermoelectric material generating the donor-like effect specifically comprises the following steps of:

1) a commercial zone-melting block (Bi) sold by Hangzhou large and thermal-magnetic electronics Limited is prepared by the method disclosed in the literature, "Tuning Multiscale Microstructures to Enhance thermal electric Performance of n-Type Bismuth-Telluride-Based Solutions₂Te_2.79Se_0.21) Ball milling is carried out for 20 minutes at the frequency of 20Hz by using a ball milling method to obtain polycrystalline powder which generates donor-like effect (in the literature, the carrier concentration of the powder obtained by crushing by using the ball milling method is increased sharply relative to a zone-melting ingot body, the Seebeck coefficient is reduced, and the powder is determined to generate obvious donor-like effect);

2) subjecting the polycrystal Bi which is obtained in the step 1) and generates the donor-like effect to₂Te_2.79Se_0.21The powder-based thermoelectric material is used as a raw material and is put into a quartz glass tube to be vacuum-sealed to 10^-6torr；

3) Putting the quartz glass tube obtained in the step 2) into a muffle furnace, heating to the melting temperature of 1123K, and preserving heat for 24h to obtain a bismuth telluride blank material with the donor-like effect initially;

4) putting the bismuth telluride blank material with the donor-like effect obtained in the step 3) into a zone melting furnace, and performing annealing at 1123K for 10mm h^-1The high-orientation bismuth telluride-based single crystal material obtained by the growth at the pulling speed is the bismuth telluride-based thermoelectric material eliminating the donor-like effect.

The test results show that the telluride eliminating donor-like effect obtained in example 1The bismuth-based thermoelectric material sample can obtain higher room-temperature conductivity of 9.24 multiplied by 10⁴S m^-1The conductivity decreases gradually with increasing temperature. The absolute value of the Seebeck coefficient first increases with increasing temperature and subsequently decreases with increasing temperature. Example 1 the bismuth telluride-based thermoelectric material sample with the donor-like effect eliminated obtained a Seebeck coefficient of-222. mu. VK at room temperature^-1. The power factor is gradually reduced along with the temperature rise, and the sample of the bismuth telluride-based thermoelectric material eliminating the donor-like effect obtained in the example 1 has the maximum power factor of 4.6mWm at room temperature^-1K^-2. The total thermal conductivity first shows a decreasing trend with increasing temperature, and then gradually increases with the influence of bipolar thermal conductance. The dimensionless thermoelectric figure of merit ZT of the bismuth telluride-based thermoelectric material sample 300K obtained in example 1 in which the donor-like effect was eliminated was 1.0, and the maximum ZT was obtained at 350K_max＝1.10。

Comparative example 1

Comparative example 1 differs from example 1 in that: omitting steps 2) and 3), and obtaining the polycrystal Bi which generates donor-like effect and is obtained in the step 1)₂Te_2.79Se_0.21And (3) directly sintering and densifying the powder-based thermoelectric material to perform performance test.

Comparative example 1 compared to a raw material commercial zone-melting block (electrothermal transport properties at room temperature can be seen in table 1), although the orientation was significantly reduced, the conductivity at room temperature was drastically increased to 16.67 × 10 due to a large increase in the electron concentration⁴S m^-1It is apparent that comparative example 1 is affected by the donor-like effect as the temperature gradually decreases. The Seebeck coefficient of comparative example 1 is significantly reduced due to the significant increase in electron concentration caused by the donor-like effect, and is only-107. mu. V K at room temperature^-1Its absolute value increases with increasing temperature; the power factor gradually decreased as the temperature increased, but comparative example 1 could obtain the maximum power factor of only 1.9mWm at room temperature due to the significant decrease of the Seebeck coefficient^-1K^-2. The total thermal conductivity firstly shows a decreasing trend along with the increase of the temperature, and then gradually increases along with the influence of the bipolar thermal conductivity, but the temperature which is significantly influenced by the bipolar diffusion is higher due to the significant increase of the carrier concentrationThe temperature intervals are shifted. The total thermal conductivity of comparative example 1 was significantly improved due to the increase in the thermal conductivity of electrons, and a dimensionless thermoelectric figure of merit ZT of 0.32 was obtained at 300K, and a maximum ZT was obtained at 473K_max＝0.54。

Comparative example 2

Comparative example 2 differs from example 1 in that: step 3) is omitted, and the performance test is directly carried out by using the block obtained by melting.

Comparative example 2 the texture was destroyed, but the carrier concentration was greatly increased and the conductivity at room temperature was 16.09X 10⁴S m^-1And gradually decreases with increasing temperature, it is understood that comparative example 2 is still affected by the donor-like effect. The Seebeck coefficient of comparative example 2 is significantly reduced due to the significant increase in electron concentration caused by the donor-like effect, and is only-105. mu. v K at room temperature^-1The absolute value of which increases with increasing temperature. The power factor gradually decreased with increasing temperature, but comparative example 2 could obtain the maximum power factor of only 1.7mWm at room temperature due to a significant decrease in Seebeck coefficient^-1K^-2. The total thermal conductivity firstly shows a decreasing trend along with the increase of the temperature, and then gradually increases along with the influence of the bipolar thermal conductivity, but due to the obvious increase of the carrier concentration, the temperature which is obviously influenced by the bipolar diffusion shifts to a high-temperature interval. The total thermal conductivity of comparative example 2 was significantly improved due to the increase in the electronic thermal conductivity, and the dimensionless thermoelectric figure of merit ZT was 0.31 at 300K and the maximum ZT was obtained at 423K_max＝0.45。

Table 2 room temperature carrier concentration of the final products in example 1 and comparative examples 1 and 2

From the above performance tests, the sample of example 1 has a carrier concentration and Seebeck coefficient similar to those of the raw material commercial zone-melting block (room temperature thermoelectric properties are shown in table 1). Indicating that the donor-like effect in the final product obtained in this example 1 is eliminated. Once the donor-like effect occurs, the electron carrier concentration in the material is greatly increased. The method is embodied in macroscopic performance, and for the n-type bismuth telluride-based thermoelectric material, the carrier concentration is greatly improved and deviates from the optimal interval. Due to the increase of the carrier concentration, the conductivity of the sample can be remarkably increased, the absolute value of the Seebeck coefficient can be greatly reduced, and the power factor is seriously degraded, so that the comparative example 1 and the comparative example 2 can be seen. In example 1, the donor-like effect is eliminated, the carrier concentration is recovered to be a better value, the Seebeck coefficient is basically kept unchanged, the power factor is obviously improved compared with comparative example 1 and comparative example 2, and finally the dimensionless thermoelectric figure of merit ZT is optimized. While it can be seen by comparison with the final product of comparative example 2 that such a zone-melting process is indispensable, the donor-like effect is still present and no bulk is obtained that eliminates the donor-like effect, simply by melting the original material that has already generated the donor-like effect.

CN112670399A Bi₂Te₃Method for eliminating donor-like effect of base thermoelectric material discloses the principle of donor-like effect generated during ingot crushing, which is essentially that oxygen occupies the position of Te, which forms Bi-O-Te cluster in the matrix₂Te_2.79Se_0.21The segregation coefficient in the matrix is very small, and after zone melting, Bi-O-Te clusters and Bi₂Te_2.79Se_0.21The substrate is selectively crystallized to cluster Bi-O-Te with Bi₂Te_2.79Se_0.21Separating the matrix to purify Bi₂Te_2.79Se_0.21The effect of the matrix is to essentially eliminate the donor-like effect. However, CN112670399A is not concerned with mentioning how donor-like effects should be eliminated for samples that have already generated donor-like effects.

In conclusion, through the specific preparation process, the method can eliminate the donor-like effect generated by the bismuth telluride-based thermoelectric material, recover the bismuth telluride-based thermoelectric material sample generating the donor-like effect to eliminate the donor-like effect, recycle the original material without use value, greatly reduce the preparation cost of the bismuth telluride-based thermoelectric material, and is beneficial to large-scale industrial production.

The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, many modifications and changes can be made without departing from the inventive concept of the present invention, and these modifications and changes are within the protection scope of the present invention.