阅读说明：本技术 一种p型碲化铋热电材料及其制备方法 (P-type bismuth telluride thermoelectric material and preparation method thereof ) 是由 刘峰铭 于 2020-08-03 设计创作，主要内容包括：本发明公开了一种P型碲化铋热电材料及其制备方法,所述制备方法以Bi、Sb、Te单质粉末为原料,进行球磨,然后进行等离子体烧结,制备块体材料,即为P型碲化铋热电材料。本发明具有工艺简单、生产周期短和生产效率高的特点,所制备调制的碲化铋基热电块体材料纯度高、热导率低、电导率高、机械强度高。(The invention discloses a P-type bismuth telluride thermoelectric material and a preparation method thereof. The method has the characteristics of simple process, short production period and high production efficiency, and the prepared bismuth telluride-based thermoelectric bulk material has high purity, low thermal conductivity, high electrical conductivity and high mechanical strength.)

1. A preparation method of a P-type bismuth telluride thermoelectric material is characterized by comprising the following steps:

(1) taking Bi, Sb and Te elementary substance powder as raw materials, weighing and proportioning the raw materials according to a stoichiometric ratio, and putting the raw materials into a stainless steel ball-milling tank which is arranged in a glove box protected by inert gas;

(2) taking the stainless steel ball milling tank filled with the materials out of the glove box, and filling the ball milling tank mixed with 5% of H₂Ar-H of (A-A)₂Mixing gas;

(3) putting the ball milling tank into a planetary ball mill, and carrying out ball milling to obtain powder, wherein the obtained powder is pre-synthesized bismuth telluride powder;

(4) transferring the ball milling tank into a glove box protected by inert gas, opening the ball milling tank, and filling the pre-synthesized bismuth telluride powder into a graphite mold;

(5) and (3) placing the graphite mold filled with the powder into a plasma sintering furnace, and placing the graphite mold between graphite gaskets in the plasma sintering furnace for sintering to prepare a block material, namely the P-type bismuth telluride thermoelectric material.

2. The method for preparing a P-type bismuth telluride thermoelectric material as claimed in claim 1, wherein the purity of elementary substance powder of Bi and Sb in the step (1) is not less than 99.99%, and the purity of elementary substance powder of Te is not less than 99.999%.

3. The preparation method of the P-type bismuth telluride thermoelectric material as in claim 1, wherein the ball milling in the step (3) is to mix the original powder for 1-3h under the condition of 100-300rmp/min, and after the original powder is mixed uniformly, the ball milling is carried out for 4-10h under the condition of 250-350rmp/min to realize mechanical alloying, and the ball milling is carried out for 1-2h and the cooling is carried out for 10-30min in the ball milling process.

4. The method for preparing a P-type bismuth telluride thermoelectric material as in claim 1, wherein the sintering process in the step (5) is as follows:

(1) firstly, heating the furnace body to 350-480 ℃ without applying pressure, and preserving heat for 30 min;

(2) then applying axial pressure of 50-100MPa, and extruding the block body at the extrusion speed of 5-10 mm/min;

(3) the whole extrusion process is completed in air or vacuum or inert atmosphere, and the temperature is kept at 350-.

5. The method for preparing a P-type bismuth telluride thermoelectric material as claimed in claim 4, wherein the step (3) of the sintering process is vacuumized to 2-5 Pa.

6. The method for preparing a P-type bismuth telluride thermoelectric material as in claim 1, wherein the bulk material is cylindrical, and has a diameter of 10-60mm and a height of 5-20 mm.

7. The method for producing a P-type bismuth telluride thermoelectric material as claimed in claim 1, wherein the inert gas is Ar or He gas atmosphere.

8. The P-type bismuth telluride thermoelectric material prepared by the preparation method of the P-type bismuth telluride thermoelectric material as claimed in any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of thermoelectric materials, in particular to a P-type bismuth telluride thermoelectric material and a preparation method thereof.

Background

In recent years, the problems of environmental pollution, energy shortage and the like are increasingly prominent, and the human survival and social development are severely restricted, so that the development of clean energy and new energy technology becomes the focus of international social attention at present. The thermoelectric conversion technology is used as an environment-friendly new energy technology, and the Seebeek effect and the Peltier effect of thermoelectric materials can be utilized to realize direct interconversion of heat energy and electric energy. Bi₂Te₃The base compound is a thermoelectric material which is most mature in development and most widely applied at present, and has great potential in the fields of thermoelectric refrigeration and low-temperature thermoelectric power generation. At present, the bulk preparation of n-type and p-type Bi is commercially mainly carried out by the zone-melting method (ZM)₂Te₃The maximum thermoelectric figure of merit ZT of the base compound can reach about 1.0, but the zone-melting material has high preferred orientation and forceThe poor chemical property leads to low yield, more processing defects and easy damage in the using process. In addition, Bi₂Te₃The system experiences large and long-term thermal cycling and vibrational stress when applied to thermoelectric power generation, thereby improving zone-melting Bi₂Te₃The mechanical property and the mechanical processability of the base material have important significance for improving the long-term stability and the reliability of the device and widening the application field of the device.

Chinese patent ZL03150425.6 discloses a preparation method of a high-strength high-performance bismuth telluride-based sintered material, which takes a zone-melting crystal bar as a starting material, and the block material is obtained by powder preparation, screening and discharge plasma (or hot-pressing) sintering. The method has the advantages that the powder preparation process is complex, impurities are easy to introduce, partial powder needs to be eliminated after screening, the utilization rate of materials is reduced, the orientation degree of a sintering material in the direction parallel to the (001) is reduced, the performance figure of merit is reduced, and the refrigeration temperature difference of the refrigeration assembly is much lower than that of the conventional assembly.

At present, about 200 thermoelectric material systems exist, wherein the most widely applied thermoelectric material is a bismuth telluride-based thermoelectric material, but at present, the manufacturing method of the domestic bismuth telluride thermoelectric material, especially the p-type bismuth telluride-based thermoelectric material is single, and because the incomplete reaction possibly exists in the mechanical alloying process, two processes of phase synthesis and sintering exist in the discharge plasma sintering process. Li et al, by mixing 0.4 vol.% of SiC nanoparticles in a BiSbTe matrix, combined with high energy ball milling and spark plasma sintering processes, improved Seebeck coefficient and electrical conductivity, reduced thermal conductivity, and finally achieved a maximum ZT value of 1.33 at 373K. However, when the p-type bismuth telluride-based thermoelectric material is prepared by applying a powder metallurgy process, the lattice thermal conductivity is reduced, and meanwhile, due to the introduction of a large number of crystal boundaries and randomly oriented nano-crystalline grains, the mobility of carriers in the material is also remarkably reduced, so that the resistivity of the material is inevitably increased, and the ZT value is improved to a limited extent.

Disclosure of Invention

The invention aims to provide a preparation method for synthesizing a p-shaped bismuth telluride-based thermoelectric bulk material by adopting Mechanical Alloying (MA) and Spark Plasma Sintering (SPS), so as to solve the problems in the prior art.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a preparation method of a P-type bismuth telluride thermoelectric material, which comprises the following steps:

(1) bi, Sb and Te simple substance powder is taken as raw materials, ingredients are weighed according to the stoichiometric ratio, and the prepared nominal chemical component is Bi_0.4Sb_1.6Te₃The P-type bismuth telluride thermoelectric material is prepared by loading the raw materials into a stainless steel ball-milling tank, and placing the stainless steel ball-milling tank in a glove box protected by inert gas;

(2) taking the stainless steel ball milling tank filled with the materials out of the glove box, and filling the ball milling tank mixed with 5% of H₂Ar-H of (A-A)₂Mixing gas;

(3) putting the ball milling tank into a planetary ball mill, and carrying out ball milling to obtain powder, wherein the obtained powder is pre-synthesized bismuth telluride powder;

(4) transferring the ball milling tank into a glove box protected by inert gas, opening the ball milling tank, and filling the pre-synthesized bismuth telluride powder into a graphite mold;

(5) and (3) placing the graphite mold filled with the powder into a plasma sintering furnace, and placing the graphite mold between graphite gaskets in the plasma sintering furnace for sintering to prepare a block material, namely the P-type bismuth telluride thermoelectric material.

As a further improvement of the invention, in the step (1), the purity of the elementary substance powder of Bi and Sb is more than or equal to 99.99 percent, and the purity of the elementary substance powder of Te is more than or equal to 99.999 percent.

As a further improvement of the invention, the ball milling in the step (3) is to firstly mix the original powder for 1-3h under the condition of 100-.

As a further improvement of the invention, the sintering process of the step (5) is as follows:

(1) firstly, heating the furnace body to 350-480 ℃ without applying pressure, and preserving heat for 30 min;

(2) then applying axial pressure of 50-100MPa, and extruding the block body at the extrusion speed of 5-10 mm/min;

(3) the whole extrusion process is completed in air or vacuum or inert atmosphere, and the temperature is kept at 480 ℃ of 350-.

As a further improvement of the invention, in step (3) of the sintering process, a vacuum is applied to 2-5 Pa.

As a further improvement of the invention, the block material is a cylinder with the diameter of 10-60mm and the height of 5-20 mm.

As a further improvement of the present invention, the inert gas is Ar or He gas atmosphere.

The invention also provides the P-type bismuth telluride thermoelectric material prepared by the preparation method of the P-type bismuth telluride thermoelectric material.

The invention discloses the following technical effects:

in the process of ball milling, collision and grinding are generated between the grinding balls and the powder raw materials, so that the powder is continuously subjected to deformation, cold welding and crushing, in the process, the energy of the grinding balls running at a high speed is gradually transferred to the powder, the increase and the refinement of the powder contact surface provide conditions for the mutual diffusion of atoms, and finally, a new phase is synthesized through the complex physical and chemical process. Because the ball milling is a process of mixing and refining the powder, the raw material powder prepared by the method has fine particles and no macroscopic element segregation, and the secondary ball milling method can ensure that Sb is uniformly dispersed in Bi₂Te₃In the matrix, the subsequent sintering is facilitated to obtain a high-quality block material. In addition, the mechanical alloying process does not involve high temperature, has high safety coefficient, and low-melting-point elements such as Sb, Te and the like are less volatilized, so that the components are more easily controlled. Because the crystal grains are uniformly refined to the same size, the prepared thermoelectric material has stable performance and good repeatability, the ZT value of the p-type bismuth telluride-based thermoelectric bulk material prepared by the invention is larger, the maximum ZT value can be obtained at 373K and is 1.45, the whole operation process is carried out under the inert gas protection atmosphere, and the introduction of oxide impurities is avoided. The thermoelectric polycrystalline block material is prepared by phase synthesis, powdering and block sintering. Wherein the mechanical alloying comprises phase synthesisAnd powdering, and two processes of phase synthesis and sintering exist in the spark plasma sintering process. The method has the characteristics of simple process, short production period and high production efficiency, and the prepared p-type bismuth telluride-based thermoelectric bulk material has high purity, low thermal conductivity, high electrical conductivity and high mechanical strength.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

Fig. 1 is an XRD pattern of the p-type bismuth telluride-based bulk thermoelectric material prepared in example 1 of the present invention;

FIG. 2 is an SEM image of a fracture of a p-type bismuth telluride based polycrystalline bulk thermoelectric material prepared by the method of the present invention;

FIG. 3 is a schematic view of the mechanical alloying process of the present invention.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The compressive strength of the block material in the examples of the present invention was measured using an Instron 5882 electronic universal material universal tester, the samples were strip cylinders measuring 6mm x 3mm, and the data were averaged over 5 samples.