GB2589238A

GB2589238A - Five-elements n-type thermoelectric material realizing powder allow sintering phase transformation based on crystal topology, and preparation method

Info

Publication number: GB2589238A
Application number: GB2019532.7A
Authority: GB
Inventors: Luo Yiping; Lin Bin
Original assignee: Leizip Guangdong Thermoelectric Technologies Co Ltd; Leizip Guangdong Thermoelectric Tech Co Ltd
Current assignee: Leizip Guangdong Thermoelectric Technologies Co Ltd; Leizip Guangdong Thermoelectric Tech Co Ltd
Priority date: 2018-05-10
Filing date: 2018-10-10
Publication date: 2021-05-26
Anticipated expiration: 2038-10-10
Also published as: GB202019532D0; GB2589238B; GB2589238A8; CN108649115A; CN108649115B; WO2019214158A1

Abstract

A five-elements n-type thermoelectric material realizing powder alloy sintering phase transformation based on crystal topology, and a preparation method. The chemical formula of the n-type thermoelectric material is Bi2-x-ySbxSyTe3-zSez, wherein 0.74 ≤ x ≤ 1.2, 0.04 ≤ y ≤0.06, and 0.2 ≤ z ≤0.45. Compared to other n-type thermoelectric materials, the five-elements n-type thermoelectric material experiences the transformation from a p-type alloy to a p-type powder alloy ingot and then to an n-type thermoelectric material in the preparation process, and the finally obtained five-elements n-type thermoelectric material has the advantages of high Seebeck coefficient, high electrical conductivity, low thermal conductivity coefficient, high ZT value and excellent thermoelectric properties. A thermoelectric chip is manufactured by using a five-elements p-type thermoelectric material and a five-elements n-type thermoelectric material in the five-elements thermoelectric material system, and has good thermoelectric performance and a high thermoelectric conversion rate.

Description

Five-elements N-type Thermoelectric Material Realizing Powder Alloy Sintering Phase Transformation Based on Crystal Topology, and Preparation Method

Cross-reference to Related Application

The present disclosure claims the priority to the Chinese patent application with the filing number 2018104428223 filed on May 10; 2018 with the Chinese Patent Office and entitled "Five-element N-type Thermoelectric Material Realizing Powder Alloy Sintering Phase Transformation Based on Crystal Topology, and Preparation Method", the contents of which are incorporated herein by reference in entirety.

Technical Field

The present disclosure relates to the field of thermoelectric material, in particular, to a five-element n-type thermoelectric material realizing powder alloy sintering phase transformation based on crystal topology, and a preparation method..

Background Art

The thermoelectric material is a functionai material that realizes direct conversion of thermal energy and electrical energy with each other using carrier movement inside a solid. With the rapid development of industrial level, it is necessary to find a sustainable clean energy source. Among numerous new energy sources, devices made of a thermoelectric material not only can be used for thermoelectric power generation, but also c:an be used for thermoelectric refrigeration, without using a transmission component during application, thus having many advantages such as small volume, light weight, and no noise in operation. Most importantly; the thermoelectric materials are not likely to cause environmental pollution, have a long service life, and are easy to control. Thus, the thermoelectric materials have a wide range of application prospects and a huge value of use.

However; applications of the thermoelectric materials currently are still limited; mainly for the following reasons: (1) poor thermoelectric properties and low thermoelectric conversion efficiency of the thermoelectric materials; (2) poor matching property between p-type material and n-type material of thermoelectric chips.

Therefore, it is urgent to provide a method capable of improving the properties of the thermoelectric material and enhancing the matching degree between the n-type material and the p-type material in the art, so as to improve the conversion rate of the thermoelectric chips and promote the application of the thermoelectric chips.

Summary

The objectives of the present disclosure include providing a five-element n-type thermoelectric material, wherein compared with other n-type thermoelectric materials, the five-element n-type thermoelectric material of the present disclosure has the advantages of a high Seebeck coefficient, high electrical conductivity and a low thermal conductivity coefficient, so as to have a high ZT value and excellent thermoelectric properties.

The objectives of the present disclosure further include providing a five-element thermoelectric material system, wherein the thermoelectric material system includes a five-element p-type thermoelectric material and the foregoing five-element n-type thermoelectric material, wherein the p-type material and the n-type material have similar Seebeck coefficients; electrical conductivity and thermal conductivity coefficients; Good matching property, and a high thermoelectric conversion rate.

The objectives of the present disclosure further include providing a preparation method for the foregoing five-element n-type thermoelectric material, wherein the five-element n-type thermoelectric material manufactured thereby has the advantages of a high ZT value and excellent thermoelectric properties; Optionally, in the method of the present disclosure, the production is carried out in a manner of first mixing powder and then smelting the powder, in a preparation process, and compared with the conventional rocking smelting and mixing method, the method of the present disclosure is safer, and easy to realize mass industrial production, with single furnace yield no less than 80 Kg; Optionally, in the sintering process of the method of the present disclosure, a blank is extruded using a thermal expansion aluminum alloy; the migration diffusion of substances and compression of the blank are realized simultaneously, so that the density of the thermoelectric material obtained after the sintering is completed is approximate to the density of the alloy body.

The objectives of the present disclosure further include providing use of the foregoing five-element thermoelectric material system in preparation of a thermoelectric chip, and trends of numerical values of Seebeck coefficients; resistivity and ZT values of the five-element pi-type material and n-type material used in the use of the present disclosure are extremely close to each other at dillerent temperatures, with good matching property, therefore; the manufactured thermoelectric chip has good thermoelectric properties and a high thermoelectric conversion rate.

The objectives of the present disclosure further include providing a thermoelectric chip, of which a p-n galvanic couple arm is prepared by the foregoing five-element thermoelectric material system, and which has the advantages of good thermoelectric properties and a high thermoelectric conversion rate.

In order to achieve at least one of the above objectives of the present disclosure, the following technical solution is adopted: a five-element n-type thermoelectric material, wherein the chemical formula of the n-type thermoelectric material is Bi2_,,"SbxSyTe3_,Se7, where 0.745.x.s'.:1 2, 0.04s:yi.s.:0.06, The five-element n-type thermoelectric material of the present disclosure is a novel thermoelectric material, belonging to a trigonal crystal system, wherein primitive cell is in rhombohedron, with the lattice constant ranging 1.0473-1.0587 nm; and the density ranging 6.8-6.7 Worn 3.

The elements involved in the thermoelectric material of the present disclosure include Bi, Sb, 5, Te and Se, and by adjusting the ratio of the five elements according to differences between atomic radii of respective constituent elements and electronegadvity combination; a five-element solid solution n-type alloy thermoelectric material system with dot and line defects and lattice distortion is obtained. In the above, by adjusting the ratio of the five elements; especially the molar mass ratio of Si and Sb elements, in cooperation with a preparation method for realizing powder alloy sintering phase transformation based on crystal topology, he transformation of p-type alloy to p-type powder alloy blank and then to n-type thermoelectric material is experienced in the preparation process, and finally the hve-element n-type thermoelectric material is obtained. Moreover, Se and S participate in formation of lattice distortion, and especially the addition of S can generate relatively large distortion to the lattice. The thermal conduction is suppressed by adjusting the molar mass ratio of Se and 5, etc., and finally an n-type thermoelectric material with a low thermal conductivity coefficient is obtained Specifically, the n-type thermoelectric material of the present disclosure has a thermal conductivity coefficient of 0.3-0.5 whit K, which is only 30-60% of the conventional n_-type Bi2Te3 thermoelectric material, and an average ZT value greater than 1; which is 30-50% higher than that of the conventional n-type Bi2Te: thermoelectric material.

To sum up, the five-element n-type thermoelectric material provided in the present disclosure exhibits excellent thermodynamic properties; a high Seebeck coefficient, low resistivity and a low thermal conductivity coefficient.

In some specific embodiments, the x is 0.74, 0.95 or 1.2.

In some specific embodiments, the y is 0.04, 0.05 or 0.06.

In some specific embodiments; the z is 0.2, 0.35 or 0.45.

In some specific embodiments, the chemical formula of the n-type thermoelectric material is B10.74Sb1.2So.o6Te2.s5Seo4s.

In some specific embodiments, the chemical formula of the n-type thermoelectric material is Bit0Sb0.9530.05Te2.65Se0.35.

In some specific embodiments, the chemical formula of the n-type thermoelectric material is Bii.225b0.7450.04Te2.808eo.20.

In some specific embodiments, the bandgap of the five-element n-type thermoelectric material is 0_29-0.31 eV.

In some specific embodiments, the bandgap of the five-element n pe thermoelectric material is 0.29 eV, 0.30 eV or 0.31 eV.

The present disclosure further relates to a five-element thermoelectric material system, wherein the thermoelectric material system includes a five-element p-type thermoelectric material and the foregoing five-element n-type thermoelectric material, wherein the chemical formula of the five-element p-type thermoelectric material is Bii2_,""Sb$,Te3_,Sez, where 1.4.sxs1.6, 0.02sys0.15, 0.025szs0.15.

Since the p-type material and the n-type material involved in the present disclosure have similar Seebeck coefficients, electrical conductivity and thermal conductivity coefficients, the five-element thermoelectric material system of the present disclosure has the advantages of good matching property between the p-type thermoelectric material and the n-type thermoelectric material, and a high thermoelectric conversion rate, thus being particularly suitable for preparing thermoelectric chips.

In some specific embodiments, in the five-element p-type thermoelectric material, x is 1.4, 1.5, 1.6, 1.7, 1.8 or 1.9; y is 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13; 0.14, 0.15; and z is 0.025, 0.05, 0.075, 0.1, 0.125; 0.15.

In some specific embodiments, the chemical formula of the five-element p-type thermoelectric material is Bio.eSbi.je2ASeo 380 028.

In some specific embodiments, the chemical formula of the five-element p-type thermoelectric material is BOASb1TP * -2.7-0.15-0.15.

The present disclosure further relates to a preparation method for the foregoing five-element n-type thermoelectric material, and in the method, elemental powder Bi, Sb, S, Te and Se is mixed, smelted, pulverized, cold-pressed and sintered according to the chemical formula Bi2-ySbxSyTe3aSez, so as to obtain a molded n-type thermoelectric material.

Specifically, the preparation method of the present disclosure undergoes the following physical changes in the preparation process: forming a p-type alloy by smelting; pulverizing and cold-pressing the p-type alloy to prepare a p-type powder alloy block; and sintering the p-type powder alloy block to obtain the five-element n-type thermoelectric material.

The method of the present disclosure realizes the powder alloy sintering phase transformation based on crystal topology, and thus realizes the transformation of the p-type thermoelectric material to the n-type thermoelectric material. Specifically; in the method of the present disclosure, first the p-type alloy blank is obtained by mixing, smelting and cold-pressing the elementary substances, and then the p-type alloy thermoelectric material that is homogenous and of the same crystal as the p-type alloy blank is obtained by sintering the p-type alloy blank. In the above, in the sintering process; the method of the present disclosure utilizes spatial topological structure constraints of the alloy rnicropowder particulate material, ratio of surface isolated atoms and associated atoms, density, electronegativity, bond length, bond energy and other surface states, to control the mutual diffusion migration of some atoms in each component between the particles; thereby completing the crystal structure topology and phase transformation, and finally realizing reversing of the conductive polarity of carriers, and thus converting into the n-type thermoelectric material.

In addition, the conventional smelting method of alloy is a rocking smelting and mixing method, and as the boiling point of the elementary substance S is only 445 "C, if the rocking smelting and mixing method is used during high-temperature smelting, the partial pressure of S in the container is easily increased suddenly during the rocking process, causing air pressure oscillation and thus causing explosion. Therefore, in the method of the present disclosure, the powder is mixed first, and then smelted, thus improving the safety of the reaction, and easily realizing mass industrial production, with single furnace yield no less than 80 Kg.

In some specific embodiments, the mixing of the powder includes: adding the elementary substances into a vacuum container in proportion, and rotationally mixing the same under a protective atmosphere.

In some specific embodiments, the rotational speed of the rotational mixing is 30-100 r/min, and the duration is 15-40 h; Preferably, the rotational speed of the rotational mixing is 30 rimin, 40 r/rnin, 50 rimin, 60 rimin, 70 r/min, 80 rimin, 90 rimin or 100 r/rnin; and the duration of the rotational mixing is 15 h, '15 h, 17 h, 18 h, 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h, 28 h, 29 h or h; More preferably, the rotational speed of the rotational mixing is 50 rimin, and the duration of the rotational mixing is 30 h. In some specific embodiments, the elementary substances are all powder.

In some specific embodiments, the purity of the elementary substances is 4 N N. In some specific embodiments, the vacuum container is a vacuum ball mill.

In some specific embodiments, the protective atmosphere is nitrogen or an inert gas; more preferably; the protective atmosphere is an inert gas; and the inert gas is helium, neon or argon; and most preferably, the inert gas is argon.

In some specific embodiments, the smelting specifically includes: smelting the mixed elementary substances in a vacuum sealed state, with the smelting temperature being 660-680 it, the smelting duration being 45-48 h, and after finishing the smelting, naturally cooling the resultant to room temperature, to obtain a thermoelectric material alloy ingot.

In some specific embodiments, the smelting temperature is 660 °C, 670 'C, 680 'C, 690 C or 700 ''C.

In some specific embodiments, the smelting duration is 45 h, 46 h or 48 h. In some specific embodiments, the smelting temperature is 660 CC, and the smelting duration is 45 h. In some specific embodiments, the container for smelting the mixed elementary substances is a quartz tube, one end of the quartz tube is sealed, and after the elementary substances are loaded into the quartz tube, the quartz tube is evacuated, arid the quartz tube is heated until the quartz tube is sealed by melting, and the sealed quartz tube is used for smelting.

In some specific embodiments, an outer diameter of the quartz tube is 30-40 mm, and preferably, an outer diameter of the quartz tube is 35 mm; and the length of the quartz tube is 200-1200 mm, and preferably, the length of the quartz tube is 1000 mm.

In some specific embodiments, the vacuum degree of the quartz tube is less than 10 pa.

In some specific embodiments, the quartz tube is heated at a position at least 10 cm from a sample interface formed by the elementary substances in the quartz tube; so as to form the sealed quartz tube by melting.

In some specific embodiments, the heating furnace is a resistance heating furnace.

In some specific embodiments, the pulverizing specifically includes: coarsely pulverizing the alloy obtained by smelting: and then further crushing the alloy under a protective atmosphere to a particle size thereof of 250-270 meshes, to obtain alloy powder.

In some specific embodiments, the alloy powder has a particle size of 250 meshes, 260 5 meshes or 270 meshes.

In some specific embodiments,he manner or further crushing the alloy is ball milling. In some specific embodiments, the duration of the ball milling is 15-30 h. In some specific embodiments, the duration of the ball milling is 15 h, 16 h, 17 h, 1 19 h, 20 h, 21 h, 22 h, 23 h, 24 h, 25 h, 26 h, 27 h, 28 h, 29 h 01 30 h, In some specific embodiments, the protective atmosphere is nitrogen or an inert gas; more preferably, the protective atmosphere is an inert gas, and the inert gas is helium, neon or argon; and most preferably, the inert gas is argon.

In some specific embodiments, the cold-pressing specifically includes: pressing the pulverized alloy powder into a blank in a manner of cold isostatic pressing.

In some specific embodiments, the cold isostatic pressing is accomplished by a hydraulic press.

In some specific embodiments, after the cold isostatic pressing, the density of th.e blank is no less than 96% of that of the molded n-type thermoelectric material.

In some specific embodiments, the sintering specifically includes: placing the blank into 20 a cavity of a clamp, and placing the clamp into a sintering furnace for sintering and molding.

In some specific embodiments, the temperature of the blank when being sintered is 60-85% of the temperature when being smelted.

In some specific embodiments, the temperature of the blank when being sintered is 25 60%, 65%, 70%, 75%, 80% or 85% of the temperature when being smelted.

In some specific embodiments, the duration of the sintering is 4-6 h. In some specific embodiments, the duration of the sintering is 4 h, 5 h Of 6 h. The present disclosure further relates to use of a five-element p-type thermoelectric material and a five-element n-type material in the preparation of a thermoelectric chip, 30 wherein the chemical formula of the five-element p-type thermoelectric material is Bi2a,_ ySbxSyTe3aSez, where 1.4sxs1.6, 0.02sys0.15, 0.025szs0.15; and the five-element n-type thermoelectric material is the foregoing five-element n Pe thermoelectric material.

The trends of numerical values of Seebeck coefficients, resistivity and ZT values of the five-element p-type thermoelectric material and the five-element n-type thermoelectric material adopted in the use of the present disclosure are extremely close to each other at different temperatures, with good matching property, therefore, the manufactured thermoelectric chip has good thermoelectric properties and a high thermoelectric conversion rate.

In some specific embodiments, the five-element p-type thermoelectric material and the five-element n-type thermoelectric material are used to prepare the p-n galvanic couple arm in the thermoelectric chip.

In some specific; embodiments, the thermoelectric chip is a thermoelectric power generation chip or a thermoelectric refrigeration chip.

The present disclosure further relates to a thermoelectric chip: wherein the chip includes a p-n galvanic couple arm, the p-n galvanic couple arm is prepared by the foregoing five-element thermoelectric material system, and preferably, the thermoelectric chip is a thermoelectric power generation chip or a thermoelectric refrigeration chip.

The present disclosure further relates to a thermoelectric chip, wherein the chip includes a p-n galvanic couple arm; and the p-n galvanic couple arm is prepared by the foregoing five-element thermoelectric material system.

The p-n galvanic couple arm of the thermoelectric chip of the present disclosure is prepared by the foregoing five-element p-type thermoelectric material and five-element n-type thermoelectric material. As the foregoing five-element p-type thermoelectric material and five-element n-type thermoelectric material have good matching property in terms of thermoelectric parameters, the thermoelectric chip of the present disclosure has the advantages of good thermoelectric properties and a high thermoelectric conversion rate.

In some specific embodiments, the thermoelectric chip is a thermoelectric power generation chip or a thermoelectric refrigeration chip.

Compared with the prior art, the beneficial effects of the present d 10 ure at least include: (1) compared with other n-type thermoelectric materials, the five-element n-type thermoelectric material provided in the present disclosure has the advantages of a high Seebeck coefficient, high electrical conductivity and a low thermal conductivity coefficient, therefore, it has a high ZT value and excellent thermoelectric properties; (2) the preparation method for the five-element n-type thermoelectric material provided in the present disclosure obtains the p-type blank in the manner of smelting and cold-pressing, and then completes the crystal structure topology and phase transformation by sintering, thereby realizing the reversing of the conductive polarity of carriers, and thus converting the p-type blank into the n-type thermoelectric material, and the prepared five-element n-type thermoelectric material has the advantages of a high ZT value and excellent thermoelectric properties; meanwhile, in the method of the present disclosure, the production is carried out in a manner of mixing the powder first and then smelting the mixture, thus having the advantages of high safety and easily realizing mass industrial production; moreover, the method of the present disclosure utilizes the thermal expansion aluminum alloy to extrude the blank in the sintering process, and thus realizes the migration diffusion of substances and compression of the blank simultaneously, so that the density of the resulting thermoelectric material is approximate to the density of the alloy body; and (3) the five-element thermoelectric material system provided in the present disclosure is applied to the preparation of the thermoelectric chip, and the foregoing five-element p-type thermoelectric material and five-element n-type thermoelectric material are adopted to prepare the p-n galvanic couple arm, wherein the numerical values of the Seebeck coefficients, resistivity and ZT values of the five-element p-type thermoelectric material and the five-element n-type thermoelectric material are close to each other, with good matching property, therefore, the manufactured thermoelectric chip has good thermoelectric properties, and a high thermoelectric conversion rate.

Brief Description of Drawings

In order to more clearly illustrate technical solutions in specific embodiments of the present disclosure or the prior art, accompanying drawings which need to be used for description of the specific embodiments or the prior art will be introduced briefly below. Apparently, the accompanying drawings in the description below merely show some embodiments of the present disclosure, and those ordinarily skilled in the art still could obtain other accompanying drawings in light of these accompanying drawings, without inventive effort.

FIG. 1 shows a migration mode of substances on a spherical surface in a sintering process of a preparation: method for a five-element n-type thermoelectric material according to an example of the present disclosure; and FIG. 2 shows a clamp used in the method of the present disclosure when sintering the five-element n-type thermoelectric material and the five-element p-type thermoelectric material.

Reference Signs: 1-blank sintering and diffusing mold; 2-high-temperature-resistant high-strength alloy steel jacket; 3-exhaust hole; 4-blank; 5-high-temperature-resistant alloy steel briquetting; 6-thermal expansion aluminum alloy; 7-high-temperature-resistant alloy steel screw; 8-end cap; 9-diffusion barrier layer.

Detailed Description of Embodiments

Embodiments of the present disclosure will be described in detail below in combination with examples, while a person skilled in the an would understand that the following examples are merely used for illustrating the present disclosure, but should not be considered as limitation on the scope of the present disclosure. If no specific conditions are specified in the examples, they are carried out under normal conditions or conditions recommended by manufacturers. If manufacturers of reagents or apparatuses used are not specified, they are conventional products commercially available.

The thermoelectric properties of the thermoelectric material depend on the dimensionless thermoelectric figure of merit ZT (ZT=a2 Ti(kp), where a is Seebeck coefficient; o is resistivity, and K is thermal conductivity coefficient; consisting of two parts, namely, lattice thermal conductivity coefficient and electronic thermal conductivity coefficient, T is absolute temperature, and 02/p is referred to as power factor). The higher the ZT is, the higher the thermoelectric conversion efficiency of the material is. It can be seen from the above equation that in order to improve properties of a thermoelectric conversion material, it is necessary to increase the Seebeck coefficient a or decrease the thermal conductivity coefficient K and the resistivity p. Currently, there are mainly two methods for improving the thermoelectric properties of materials: increasing the electrical conductivity of the materials or decreasing the thermal conductivity coefficient of the materials.

At present, a method for improving the electrical conductivity mainly is carried out by doping donor impurities of halogen compounds such as Se or TeI4, Cul, Agl and CuBr in an n-type material in a manner of donor doping, or by doping metal element acceptor impurities such as Sb, Al, Cu and Ag in a p-type material in a manner of acceptor doping, to increase the carrier concentration and mobility. Although the resistivity can be effectively reduced, the heat transport of carriers is significantly enhanced, so that the thermal conductivity coefficient of the material is also remarkably increased, and meanwhile, the high carrier concentration and mobility necessarily will result in a decreased Seebeck coefficient Currently, the methods for reducing the thermal conductivity coefficient generally include powder metallurgy, nanocrystallization and microcrystallization, and film formation. Although a relatively high Seebeck coefficient and a relatively low thermal conductivity coefficient can be obtained, the resistivity is increased to different extents, finally resulting in a relatively low ZT value. In addition, the nanocrystallization and microcrystallization of the material and film material preparation require hydrothermal reaction/solvent thermal reaction device, melt spinning device, electrochemical deposition, MOCVD or molecular beam epitaxy and other devices, and subsequently vacuum hot press sintering or spark plasma (SPS) sintering devices and the like are further required, thus nigh equipment investment and operation costs are demanded, and it is hard to continuously and stably carry out mass production, then at present it mainly exists in the field of laboratory and scientific researches.

The reasons why the above shortcomings are caused are mainly in the following aspects: (1) the crystal lattice of the three-element thermoelectric material formed by doping is relatively complete and ordered, and the thermal conductivity of the crystal lattice of the material cannot he well reduced, meanwhile, the relatively high carrier concentration and mobility also increase the contribution of the carriers to the thermal conduction; and the problem of a too high thermal conductivity coefficient of the material still cannot be solved; (2) the intrinsic excitation temperature of the commercial three-thermoelectric material prepared by doping is relatively low, resulting in rapid deterioration of material properties with increased temperature; and (3) the three; namely, the Seebeck coefficient, the resistivity and the thermal conductivity coefficient, have extremely complex association and influence, arid the three can hardly be well regulated by the existing technology adapted to mass commercial production (i.e. doped ternary solid solution).

In practical application, both the thermoelectric power generation chip and the thermoelectric refrigeration chip are made by connecting a plurality of pairs of p-n galvanic couple arms in series. In order for the thermoelectric power generation chip or the thermoelectric refrigeration chip to have better properties, the p-type material and the n-type material for manufacturing the chip are not only required to have a relatively high ZT value, but also required to have very good matching property therebetween, that is, the corresponding p-type and n-type materials are required to have as close curve trends and numerical values of Seebeck coefficients, resistivity and ZT values as possible within the range of use temperature. Currently, the optimal thermoelectric material in the low temperature region (room temperature-230 cc) is Bi2Te2-based thermoelectric material; and a common material system is: the n-type material is Bi2Te3s(Sex: and the p-type material is Bi2l-SbJe3. However, the matching property between the common n-type material and the common p-type material is not good enough at present, and the p-type material usually has relatively good thermoelectric properties, but the corresponding n-type material has poor thermoelectric properties, which then affects the properties of the thermoelectric chip.

In order to address at least one of the above problems, examples of the present disclosure provide a five-element n-type thermoelectric material, a preparation method, and use thereof.

In a preparation method for a five-element n-type thermoelectric material in an example of the present disclosure, elemental powder Si, Sb, 5, Te and Se is mixed, smelted, pulverized, cold-pressed and sintered according to a chemical formula Bi2_x_rSbxSyTe3mSe" (where 0.74sxts-1.2, 0.04545.0.06, 0.25,z5,0.45), so as to obtain a molded n-type thermoelectric material. The preparation method of the present disclosure undergoes the following physical changes in the preparation process: forming a p-type alloy by smelting; pulverizing and cold-pressing the p--type alloy to prepare a p-type powder alloy block, and sintering the p-type powder alloy block to obtain the five-element n-type thermoelectric material. FIG. 1 shows a migration mode of substances on a spherical surface in a sintering process of a preparation method for the five-element n-type thermoelectric material according to an example of the present disclosure. Referring to FIG. 1, a migration mode a represents substance migration through a gas phase, such as evaporation or coacervation; a miarabon mode b represents surface diffusion from a planar surface to a neck; a migration mode c represents volume diffusion from the planar surface to the neck; a migration mode d represents volume diffusion form grain boundary between two spheres to the neck; and a migration mode e represents grain boundary diffusion from grain boundary to the neck. Specific examples of the five-element n-type thermoelectric material and a preparation method thereof are as follows.

Example 1

A five-element n-type thermoelectric material, of which a chemical formula is Bio.74Sbi.2S0.061e2.55Se0.45.

(I) Preparing the foreaoing five-element n-type thermoelectric material by the following method (1) Mixing powder Corresponding amounts of Bi, Sb, 5, Te and Sc elemental powder were loaded into a vacuum ball mill according to the chemical formula of the five-element n-type thermoelectric material, argon was introduced as a protective atmosphere, and the materials were mixed at a rotational speed of 50 r/min for 30 h through rotation of the ball mill, wherein the purity of the elementary substances Bi, Sb, 5, Te and Sc was 4 N. (2) Sealing quartz tube by smelting The mixed elemental powder was loaded into a quartz tube, wherein the quartz tube had a length of 1000 mm, and an outer diameter of 35 mm, one end of the quartz tube had been sealed, after the powder was loaded into the quartz tube, the quartz tube was evacuated to a vacuum degree less than 10 pa, and the quartz tube was heated at a position at least 10 cm away from a sample interface formed by the elementary substances in the quartz tube, to form a sealed quartz tube by smelting.

(3) Smelting alloy The sealed quartz tube was placed in a resistance heating furnace, the smelting was carried out at 660 °C for 45 h, and after finishing the smelting, the quartz tube was naturally cooled to room temperature, to obtain a thermoelectric material alloy ingot (4) Pulverizing the alloy ingot After coarsely pulverizing the thermoelectric material alloy ingot obtained in step (3), the coarsely pulverized alloy material was further pulverized using a ball mill in an argon protection state, to a particle size thereof of 250 meshes, so as to obtain alloy powder.

(5) Preparing alloy blank Cold isostatic pressing molding was performed on the alloy powder in step (4) by a 500-ton hydraulic press, to form an alloy blank, wherein the density of the blank is 96% of that of the alloy material finally formed by sintering.

(6) Sintering alloy The blank in step (5) was placed into a clamp (as shown in FIG. 2), and the clamp loaded with the blank was placed in a sintering furnace for sintering, a temperature of the sintering being 60% of the temperature for smelting the alloy, and the duration of the sintering being 4 h, to obtain a molded five-element n-type thermoelectric material after finishing the sintering. FIG. 1 shows a migration mode of substances on a spherical surface in the method of the present disclosure in a sintering process. Referring to FIG. 1, a migration mode a represents substance migration through a gas phase, such as evaporation or coacervation; a migration mode b represents surface diffusion from a planar surface to a neck; a migration mode c represents volume diffusion from the planar surface to the neck; a migration mode d represents volume diffusion form grain boundary between two spheres to the neck; and a migration mode e represents grain boundary diffusion from grain boundary to the neck, (II) Property detection The following detection was carried out in the process of preparing the five-element n-type thermoelectric material, to measure its thermoelectric properties, specifically including: (1) detecting the electrical characteristics of the alloy ingot in step (2) at different temperatures. Specific detection results are shown in Table 1. According to the experimental data shown in Table 1, it can be seen that the alloy ingot in step (2) of the present example still belongs to an n-type material.

Table 1 Electrical Characteristics of Alloy Ingot at Different Temperatures Alloy Ingot Sample Sample 2 Sample Sample 4 Sample i Sample Sample Samples thickness (cm)maanetic field (mT) temperature (°C) 1 -51:3;6---- 3 --blia-a--- 1 control current (mA) --bTffe---- 500 -ITSA------ 500 1 6 7 500 30 500 50 0.138 0.138 0.138 20 40 20 500 I 500 500 20 I

I

1 70 ng

I i

120 20 i Hall voitage (my) 0.00203 0.00198 0.00184 0.00178 0.00176 I 0.00162 0.00148 1244 1251 3747 1251 8749 1 4992 1254

I

Hall coefficient (cn-PIC) 0.28031 0.27341 26 0.25443 0.32953 15 0.32721 I 0.30062 0.27403 17 17 86 35 19

I i

bulk carrier concentration (1cina) 2.23E+ 2.29E+ 2.46E+ 19 1.90E+ 19 I 19 19 1.91E I 2,08E 2.28E+ 19 1 19 19 surface carrier concentration (/cat2) 3.08E+ 3. , E+ 3.39E+ 3.51E+ 18 I 18 18 18 3.53E+ 1 3.85E+ 4.22E+

I

18 18 18 mobility (cm3A/gs) resistivity (Docm) 17.7918 16.7308 2 0.01634 185 15.1000 8 14.0595 2 0.02343 832 13.2701 I 11.6669 10.1494 2 0.01685 1 1 1 1 0.01575 509 004 0.02465 I 0.02576 0.02699 832 1 722 981 ! electrical conductivity (10 -cm) 63.4715 61.1925 59.3470 2 42.6651 7 40.5542 I 388110 3/0373 7 i 6 11 9 i 2 (2) detecting the electrical characteristics of the alloy blank in step (5). Specific detection results are shown in Table 2. According to the experimental data shown in Table 2, it can be seen that the alloy blank in step (5) of the present example still belongs to a p-type material before sintering.

Table 2 Electrical Characteristics of Alloy Blank at Different Temperatures Alloy Ingot Samples thickness (cm) Sample 1 Sample Sample I Sample Sample Sample Sample 0.076 2,.) 5 6 7 0.076.., 1 4 0.-die- -5.-6-76 5167e 0.076- I 6-.677e-

magnetic field

(mT) 500 500 500 500 500 500 500 temperature (oC) 20 30 40 50 60 70 80 control current (mA) 20 20 20 20 20 20 20 Hall voltage 0.00866 0.00789 0.00726 0.00653 0.00612 0.00555 0.00515 (my) 875 375 251 7501 5001 6248 6245 Hall coefficient 0.65882 0.59992 0.55195 0.49685 0.46550 0.42227 0.39187 (crn3/C) bulk earner 49 51 01 01 01 48 46 concentration 9.49E+1 1.04E+1 1.13E+1 1.26E+1 1.34E+1 1.48E+1 1.59E+1 (icm3) 8 9 9 9 9 9 9 surface carrier concentration 7.21E+1 7.92E+1 8.61E+1 9.56E+1 1.02E+1 1.12E+1 1.21E+1 (km') 7 7 7 7 R 8 8 --Rbijiiiii-------------S-4.. 7e7e----f16-ae-6--- 31.e-185---.-:::7e-52----1671ee-0 ----:27.-e773 ----27T2451

-

(crri3Nts) 7 3 1 5 7 4 3 resistivity 0.01894 0.01818 0.01745 0.01669 0.01595 0.01514 0.01438 (uscrn) 936 724 656 228 923 716 118 electrical conductivity 52.7722 54.9831 57.2850 59.9079 62.6596 66.0170 69.5353 4 6 7 2 5 5 4 (/0.cm) (3) detecting the electrical characteristics of the thermoelectric material in step (6) after the sintering at different temperatures. Specific detection results are shown in Table 3. It can be seen from the experimental data in Table 3 that the thermoelectric material exhibits electronegativity after sintering, reversing of carriers has been realized, and a p-type material is converted into an n-type material.

Table 3 Electrical Characteristics of Thermoelectric Material at Different Temperatures Alloy Ingot Sample 1 Sample T§ Sample 4 Sample. Sample Sample 7 Samples _ample 5 6

I 2 13

thickness 0.114 1 (cm) I 0.114 0.114 0.114 0.114 0.114 1 0.114 magnetic 500 500 500 500 500 500 500

field (riT)

temperature (°C) 22 30 40 50 60 70 80 control 20 20 20 20 20 20 20 current (mA) Hall voltage (my) - - - - - - 0.00268 0.00265 0.00262 0.00268 0.00263 0.00261 0.00256 7499 6251 4999 7495 7502 8754 8746 Hail - - - - - - -coefficient (cma/C) 0.30637 49 0.30281 0.29924 0.30637 45 0.30067 0.29353 0.29283 71 26 ao 52 8

-

bulk carrier concentratio n (/crns) surface carrier concentratio n ((cm2) 2,04E+1 9 2.06E+1 2.09E+1 -1---;2, ------------------- 2.08E+1 2.09E+1 2.13E+1 9 ------------.------------m o b i I i ty 2.33E+1 8 9 a 2.04E+1 9 9 9 2.43E 8 (crn3Nc*s) -----------------------------70.6375:.., 2 33E+1 8 2.37E+1 2.39E+1 ----------------- 2.35E+1 2.38E+1 38.9638 7 8, 8 16.0839 1 8 8 -----------r--------------- 69.8630 o6.0020 27.9898 1 20.0191 3 9 1 6 6 resistivity (0-cm) 0.00433 0.00433 0.00453 0.00786 0.01074 ' 0.01491 0.01820 683 7281 4375 3946 3039 229 261 electrical conductivity 1 (/0-cm) 230.559 2 230.713 220.558 127.177 93.0900 67.0573 54.9244 5 8 4 3 2 2 (4) detecting the Seebeck coefficients foregoing alloy ingot, alloy Hank and thermoelectric material, and detecting the thermal conductivity coefficieni. of the thermoelectric material. Specific detection results are shown in Table 4.

Table 4 Seebeck Coefficient and Thermal Conductivity of Alloy Ingot, Alloy Blank and Thermoelectric Material 5: LiV/K (300 K) Thermal Conductivity (w/m*K) alloy ingot 172 undetected alloy blank 210 undetected thermoelectric material -285

Example 2

A five-element n-type thermoelectric material, of which a chemical formula is oSbo.955005Te2 65Seo 35.

(I) Preparing the five-element n-type thermoelectric material by the following method (1) Mixing powder Corresponding amounts of Bi, Sb, 5, Te and Se elemental powder were loaded into a vacuum ball mill according to the chemical formula of the five-element n-type thermoelectric material, argon was introduced as a protective atmosphere, and the materials were mixed at a rotational speed of 50 ['min for 30 h through rotation of the ball mill, wherein the purity of the elementary substances Bi, Sb, 5, Te and Se was 4 N. (2) Sealing quartz tube by smelting The mixed elemental powder was loaded into a quartz tube, wherein the quartz tube had a length of 1000 mm, and an outer diameter of 35 mm, one end of the quartz tube had been sealed, after the powder was loaded into the quartz tube, the quartz tube was evacuated to a vacuum degree less than 10 pa, and the quartz tube was heated at a position at least 10 cm away from a sample interface formed by the elementary substances in the quartz tube, to form a sealed quartz tube by smelting.

(3) Smelting alloy The sealed quartz tube was placed in a resistance heating furnace, the smelting was carried out at 670 eC for 46 h, and after finishing the smelting, the quartz tube was naturally cooled to room temperature, to obtain a thermoelectric material alloy ingot.

(4) Pulverizing the alloy ingot After coarsely pulverizing the thermoelectric material alloy ingot obtained in step (3), the coarsely pulverized alloy material was further pulverized using a ball mill in an argon protection state, to a particle size thereof of 260 meshes, so as to obtain alloy powder.

(5) Preparing alloy blank Cold isostatic pressing molding was performed on the alloy powder in step (4) by a 500-ton hydraulic press, to form an alloy blank, wherein the density of the blank is 97% of that of the alloy material finally formed by sintering.

(6) Sintering alloy The blank in step (5) was placed into a clamp (as shown in FIG. 2), and the damp loaded with the blank was placed in a sintering furnace for sintering, a temperature of the sintering being 70% of the temperature for smelting the alloy, and the duration of the sintering being 6 h, to obtain a molded five-element n-type thermoelectric material after finishing the sintering.

(II) Property detection The following detection was carried out in the process of preparing the five-element n-type thermoelectric material, to measure its thermoelectric properties, specifically including: (1) detecting the electrical characteristics of the alloy ingot in step (2) at different temperatures. Specific detection results are shown in Table 5. According to the experimental data shown in Table 5, it can be seen that the alloy ingot in step ( of the present example still belongs to an n-type material.

Table 5 Electrical Characteristics of Alloy Ingot at Different Temperatures I Alloy Ingot Sample 1 Sample I Sample Sample 4 Sample Sample 6 Sample 7 1 0.085,-, 1 0,085 5 1 0.035 0,035 1 Samples 500, I 3 500 0.085 500 500 I thickness (cm) -I- 500 I- 1 0.085 I 0.085 -,

1 magnetic field 1 1

I (mT) 500 500 1 -I temperature I ("C) 20 30 40 50 60 70 80 I control current 1 20 20. 1 20 20 1 20 20 1 (mA) 0.00478 I --r--- . 1 0.00458 20 0.00462 4994 0.00475 t-I- 0.00438 i 1237 1241 6246 0.00443 1 0.00425 7489 ----- . I Hall voltage 1216 6245 (my) 1,- , 1 Hall coefficient 1 0.40640 51 0.38940 55 0.39312 45 0.40428 09 037665 71 0.36178 08 0.37293 66 I (cms/C) 1.54E+ 9 1.61E+ 19 1.59E+ 19 1.55E+ 19 1.66E+ 19 1.73E+ 19 1.68E+ 19 i 1 bulk carrier 1 concentration 1 (/cm3) i I surface carrier concentration 31E+ 18 I 1.36E+ 18 I 1. E+ 1 1E+ 1.41E+ 18 I 1.47E+ 18 1.42E+ 18 i 2' 18 18 1 (/e CM) 11 mobility 37.4389 1 32.1088 25.7102 20.8817 1 16.2788 2 13.0883 8 11.7218 1 1 (cm3Ahs) i! 0.01085 Q 1 0.01936 0.02313 [ 0.02764 0.03181 r resistivity [ 0.01212 i 0.01529 (2) detecting the electrical characteristics of the alloy blank in step (5). Specific detection results are shown in Table 6. According to the experimental data shown in Table 6, it can be seen that the alloy blank in step (5) of the present example still belongs to a p-type material before sintering.

Table 6 Electrical Characteristics of Alloy Blank at Different Temperatures 1 Alloy ingot Sample 1 Sample 2 Sample 3 I Sample 4 Sample 5 Sample 6 I 1 0.075 0.075 1 0.075 i 1 Samples i thickness 1 1 1 1 I 1 (cm) i 0.075 0.075 0.075

1 magnetic 1 field (mT) 500 500 500 I 500 500 500

1 temperature 1 (°C) 20 40 50 60 70 80 I control 1 20 20 20 20 20 20 1 1 current (mA) 0.007631 252 0.006281 248 + 0.004443 754 0,003999 999 I- 0.572343 9 0.471093 7 a005687 0.004981 0.333281 6 0,3 i Flail voltage 504 253 i 0.426562 I (my) 0.373594 1 1-4-11 8 1 coefficient 1 (cm3/C) i bulk carrier 1.09E+19 1.33E+19 1.47E+19 67E+19 1.88E+19 2.08E+19 i concentration i 1 (icm3) i i surface 8.19E+17 9.95E+17 1.10E+18 1.25E+18 1.41E+18 1.56E+18 1. carrier I 1 concentration 1 1 (/cm2) 1 i mobility I resistivity 26.43549 -6.--thlig-d 59 23.6908 22.52244 20.76627 19.49205 18.55055 1 6.61-67Eie-e-09 675-1-13-g3-9 0.617-6-50 -6.-0170e8-33.

I (cm3/V-s) 46 43 0.016172 1 1 1 1 (0.crn) 03 i 1 ePrrica 46.18812 50.28893 52.79982 55.58512 58.48524 1 le 61.83517 i ^"l 1 i I - - ' i conductivity (ascm) I! 516 1 841 1 061 053 815 559 616 electrical I I I 51.6514 43.2186 36.1721 31.4305 i 92.1221 i 82.4510 i 652996 conductivity i i 1 1 1 3 i 7 8 6 4 7 1 (I.C.)scm) I i I i I i I (i0scm) (3) detecting the electrical characteristics of the thermoelectric material in step (6) after the sintering at different temperatures. Specific detection results are shown in Table 7. It can be seen from the experimental data in Table 7 that the thermoelectric material exhibits eiectronegativity after sintering, reversing of carriers has been realized, and a p-type material is converted into an n-type material.

Table 7 Electrical Characteristics of Thermoelectric Material at Different Temperatures Alloy Ingot Sample 1 I Sample 1 Sample Sample Sample Sample Sample Samples 1 n 3 4 5 6 7 I ' thickness 0.082 I 0.082 1 0.082 0.082 0.082 0.082 0.082 (cm) 500 i 500 500 500 500 500 magneto held (mT) 1 500 1 temperature (°C) 23.06 1 39.97 50 59.99 70.05 80 I 30 1 i control current (mA) 20 1 20 20 20 20 20 Hall voltage 0.17783 75 1 20 - 0.17937 52 0.18860 - - (rnV) I 0.18603 01 0.19372 47 0.18501 25 1 - -ic 11 0.18501 ? -

I

Hall 0,17783 75 1 0,18603 75 - - 0,19372 47 0,18501 25 coefficient (crns/C) 3.51E+1 9 1 - 3.36E+1 0.17937 52 0.18860 3.23E+1 9 3.38E+1 9 -6-illk carrier concentration (icar3) I 0,18501 o._i 3.48E+1 9 01 I 25 3.31E-F1 9 i 3.38E+1 o _) surface carrier concentration (icm2) 2.88E1F1 I 2.77E1F1 16 I 2.75E+1 16 2.86E+1 8 2.72E+1 8 2.65E+1 8 I 2.77E+1 8 8 mobility (crnsiVes) 67.2468 69.7150 69.7289 58.4930 49.8489 38.8286 31.9389 6 7 o 8 2 7 9 resistivity (D*cm) electrical conductivity (/0-cm) 0.00264 0.00265 0.00266 0.00306 0.00378 0.00498 0.00579 4547 3839 8008 6606 3433 9217 2685 378.136 6 376.812 i 7 374.811 326.093 264.310 200.432 172.631 i 5 4 2 3 c i (4) detecting the Seebeck coefficients of the foregoing alloy ingot, alloy blank and thermoelectric material, and detecting the thermal conductivity coefficient of the thermoelectric material. Specific detection results are shown in Table 8.

Table 8 Seebeck Coefficient of Alloy Ingot, Alloy Blank and Thermoelectric Material i 1 Thermal Conductivity

I

i 5: ti1/4//K. (300 K) I Coefficient (win]. K) 1 I 1 alloy ingot 142 -1- undetected alloy blank 196 i undetected thermoelectric material -253 0.425

a Example 3

A five-element n-type thermoelectric material, of which a chemical formula is Bi1.22Sb0.7480.04Te2.80Seo.2e.

(I) Preparing the foregoing fivie-element n-type thermoelectric material by the following method (1) Mixing powder Corresponding amounts of Bi, Sb, 5, Te and Se elemental powder were loaded into a vacuum ball mill according to the chemical formula of the five-element n-type thermoelectric material, argon was introduced as a protective atmosphere, and the materials were mixed at a rotational speed of 50 r/min for 30 h through rotation of the ball mill, wherein the purity of the elementary substances Bi, St), S, Te and Se was 4 NJ.

(2) Sealing quartz tube by smelting The mixed elemental powder was loaded into a quartz tube, wherein the quartz tube had a length of 1000 mm, and an outer diameter of 35 mm, one end of the quartz tube had been sealed, after the powder was loaded into the quartz tube, the quartz tube was evacuated to a vacuum degree less than 10 pa, and the gun tube was heated at a position at least 10 cm away from a sample interface formed by the elementary substances in the quartz tube, to form a sealed quartz tube by smelting.

(3) Smelting alloy The sealed quartz tube was placed in a resistance heating furnace, the smelting was carried out at 680 uC, for 48 h, and after finishing the smelting, the quartz tube was naturally cooled to room temperature, to obtain a thermoelectric material alloy ingot.

(4) Pulverizing the alloy ingot After coarsely pulverizing the thermoelectric material alloy ingot obtained in step (3), the coarsely pulverized alloy material was further pulverized using a ball mill in an argon protection state, to a particle size thereof of 270 meshes, so as to obtain alloy powder.

(6) Sintering alloy The blank in step (5) was placed into a clamp (as shown in FIG. 2), and the clamp loaded with the blank was placed in a sintering furnace for sintering, a temperature of the sintering being 75% of the temperature for smelting the alloy, and the duration of the sintering being 6 h; to obtain a molded five-element n-type thermoelectric material after finishing the sintering.

(II) Property detection The following detection was carried out in the process of preparing the five-element n-type thermoelectric material, to measure its thermoelectric properties; specifically including: (1) detecting the electrical characteristics of the alloy ingot in step (2) at different temperatures. Specific detection results are shown in Table 9. According to the experimental data shown in Table 9; it can be seen that the alloy ingot in step (2) of the present example still belongs to an n-type material.

Table 9 Electrical Characteristics of Alloy Ingot at Different Temperatures 1 Alloy Ingot Sample 1 Sample Sample 3 ----- ----- Sample 7 1 1I - Sample 1 Sample 1 Sample 1 Samples 1 z 1 4 5 6 1 '1 ! 0.133 1 0.133 1 thickness i -------------------500 0.133 1 0.133 0.133 ------------------500 0.133 i 0.133 -------- ---------it -----------------------------i ---------------80 1 (cm) . i 40 500 500 500 i------- ---------- ---4----------I--------------- ------------------t-------------------t-------------------

1 magnetic field 50 60 70

1 500 11 500 1 (mT) i r-----------:---------------------------------I------------------1 temperature I 30 1 CC) 11 Icontrol current 1 1 (mV) 1 1247 1 6248 20 20 20 20 1 20 1 20 20 -0.00481 0.00451 0.00425 0.00405 I (rnA) 1 1 0.00495 8751 8753 0002 6251 I Hall voltage T 0.00533 t 0.00510 6251

I I 1 1

1 0.65918 0.64089 0,60099 0.56525 0.53948 i Hall I 0.70905 I 0.67913 ! coefficient (cm3IC) 59 11 14 38 42 03 13 bulk carrier 1 9.20E+1 9.48E* 16 9.75E+1 8 1.04E+ 1.I 1E-F1 E+1 concentration 1 8.81E+ 1 8 19 9 9 3.) 1 18 I surface carrier I 1.22E+1 1.26E+ 16 1.30E1 1.38E+ 18 47E+1 1.54E+1 i 1.17E+ 8 8 a concentration 1 lcm2) 1 18

I

mobility 1 36.5888 34.0445 7 32.1506 9 30.5124 6 27.9977 1 25 8787 9 24 0821 (cm3N.$) 1 5 ----------------- ------------------- --------------------- -------------- -----------------------------------0.02184 6 ---------------------------+------------- 0.01994 0.02050 0.02100 0.02146 222 0.02240 171 resistivity i 0.01937 829 267 433 585 (0eem) 1901 electrical conductivity (/0 'cm) I 46.7736 6 47.6092 4 46.5856 3 45,7828 9 44.6394 1 51.6022 50.1296 7 1 1 1

I

--I--

(2) detecting the electrical characteristics of the alloy blank in step (5) before sintering. Specific detection results are shown in Table 10. According to the experimental data shown in Table 10, it can be seen that the alloy blank in step (5) of the present example still belongs to a p-type material before sIntenng Table 10 Electrical Characteristics of Al oy Blank at Different Temperatures Alloy Ingot!Sample Sample Sample Sample 4 Sample 5 Sample 6 Sample 7 1,-,, 3 Samples 1,... i

thickness 1 0.078 0.078 1 0.078 0.078 0.078 0.078 0.078

magnetic field 1 500 500 500 500 500 500

1 500 30 40 50 60 70 80 (mT) 1 temperature 1 I 20 (°C) i control current 11 20 20 20 20 20 ---0.00037 ---6 (rnA) I --035 I 0.005-43 -0.00109-0.e00r71 875 20 20 Hall voltage 1 0i007r5T1 8748 1 7498i 375 0,05606 25 5002 --lkifiid-I 0.16136 1 0.11212 0,08531 251 1.11E-F2 0.02925 125 i 23 1 49 7.33E+1 0 017 0.03363 (my) : 8749 1 9 2.14E+2 753 i 3.87E+1 1 5.57E+1 0 1.86E+2 7± 1 0 Hall coefficient i 0.19646 9 1 9 l 1 (cm31C) 24 bulk: carrier 1 1 3.18E4-1 concentration 1 1 9 (//cm3) I surface carrier 1 2.48E+1 3.02E+1 1 4.35E+1 5.71E+1 8.70E+1 1.67E+1 1.45E+1 i concentration 1 8 8 8 8 8 9 : (/cm:2) mobility 7.52372 6.65952 4.93500 3.97980 1 279442 5 1.55976 7 1.91775 (cm?/Vs) 2 2 2 resistivity 0.02611 0.02423 0.02272 0.02143 638 0.02006 227 0.01875 291 0.01754 (0.cm) 239 032 033 01 electrical 41.2706 44.0134 46.6496 7 49.8448 53.3250 7 57.0122 38.2959 1 4 2 conductivity (10..cm) : (3) detecting the electrical characteristics or the thermoelectric material in step (6) after the sintering at different temperatures. Specific detection results are shown in Table 11. It can be seen from the experimental data in Table 11 that the thermoelectric material exhibits eiectronegativity after sintering; reversing of carriers has been realized, and a p-type material is convened into an n-type material.

Table 11 Electrical Characteristics of Thermoelectric Material at Different Temperatures 1 Alloy Ingot Sample 1 ' Sample 2 Sample 3 11 Sample 4 Sample 5 Sample 6 1 Samples 1 i 1 thickness 0.125 0.125 10125 1 0.125 0 125 0.125 i i i (cm) i

1 maanetic I field (mT) 500 500 500 I 500 500

I temperature 1 30.03 1 39.99 I 50 1 500 69.97 80.03 1 (QC) 20. 20 20;I 60 I 20 20 1 control - - - . 20 - 0.002187 505 1 current (mA) 0.002074 998 0.002037 0.002068 - 0.002218 742 0.273438 2 1 Hall voltage - 492 765 0.002199 -II (my) 0.259374 7 - - 999 0.277342 7 1 0.254686 0.258595 -i Hall 4 7 0.274999 I! coefficient 1 (cms/C) 9 1 bulk carrier 11 concentratio 2,41E+19 2.45E+19 2.42E+19 2.27E+19 2.25E+19 2.29E+19 I n (tcrn3) i 1 surface 01E+18 3.07E+18 3.02E+18 2.84E+18 2.82E+18 2.86E+18 II carrier. : I 11 conce.ntratio I* ,:\ II I I 18.04316 16.60238 ! . n Venn) _I I 6-6:15371 07 -- ---- 1 mobility 1 I 19.75197 I 19.15494 65.05727 -5.-01e4-69 I 1 22.25661 I 20.74974 0.013092 1 -6151-256 82 1 (cm3N-s) ! I 15 61 60.71712 I resistivity (0-cm) electrical conductivity (inscm) II 0ff1-18-5-3 I 0.0122574 I I 83 2 1 I I 76 38167 I 69.65435 ! I I 85.8087 I 81.47173 1

I

(4) detecting the Seebeck coefficients of the foregoing alloy ingot, alloy blank and thermoelectric material, and detecting the thermal conductivity coefficient of the thermoelectric material. Specific detection results are shown in Table 12.

Table 12 Seebeck Coefficient of Alloy Ingot, Alloy Blank and Thermoelectric Material Besides, an example of the present disclosure further provides a five-element thermoelectric material system, which includes a five-element p-type thermoelectric material and the five-element n-type thermoelectric material (Bi2..x.ySb"SyTea.,Se,., where 0.74sxs1.2, 0.04sys0.06, 0.2szs0.45) descried in the preceding of the present disclosure, wherein the chemical formula of the five-element p-type thermoelectric material is ySbxSyTe3_.,Sez, where 1.4sxs1.6; 0.02sys0.15, 0.025szs0.15.

As the p-type material and the n-type material involved in the present disclosure have similar Seebeck coefficients, electrical conductivity and thermal conductivity coefficients, the five-element thermoelectric material system of the present disclosure has the advantages of good matching property between the p-type thermoelectric material and the n-type thermoelectric material and a high thermoelectric conversion rate, and is particularly suitable for preparing thermoelectric chips. In some specific embodiments, in the five-element p-type thermoelectric material x is 1.4, 1.5; 1.6, 1.7; 1.8 or 1.9; y is 0.02, 0.03, 0.04, 0.05, 0.06, 0_07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, z is 0.025, 0.05, 0.075; 0.1; 0.125, 0.15.

The five-element p-type thermoelectric material and the five-element n-type thermoelectric material in the five-element thermoelectric material system provided in the examples of the present disclosure may be applied to prepare a thermoelectric chip; the I 5: uV/K (300 K) Thermal Conductivity Coefficient (whim K) alloy ingot I 125 undetected alloy Plank I 185 undetected thermoelectric 1-I

I

material -225 0.467 trends of numerical values of Seebeck coefficients, resistivity and ZT values of the five-element p-type thermoelectric material and the five-element n-type thermoelectric material adopted in the use are extremely close to each other at different temperatures, with good matching property, therefore, the manufactured thermoelectric chip has good thermoelectric properties and a high thermoelectric conversion rate. Specifically, the thermoelectric chip may be a thermoelectric power generation chip or a thermoelectric refrigeration chip. The five-element p-type thermoelectric material and the five-element n-type thermoelectric material in the thermoelectric material system may be used to prepare the p-n galvanic couple arm in the thermoelectric chip. Specific application examples of the thermoelectric material system are as follows.

Application Example 1 A thermoelectric power generation chip, wherein the thermoelectric power generation chip has a hot surface size of 30x30 ram, and a cold surface size of 30,434 ram, and the number of p-n electric dipole pair is 72, wherein the p-n electric dipole is made of a five-element p-type thermoelectric material and a five-element n-type thermoelectric material, wherein the chemical formula of the five-element p-type thermoelectric material is Bi04Sb1 eTe2.7Seo.1580.15, and the five-element n-type thermoelectric material is the n-type thermoelectric material in Example 1.

Application Example 2 A thermoelectric power generation chip, wherein the power generation chip has a hot surface size of 30x30 mm, and a cold surface size of 30x34 mm, and the number of p-n electric dipole pair is 72, wherein the p-n electric dipole is made of a five-element p-type thermoelectric material and a five-element n-type thermoelectric material; wherein the chemical formula of the five-element p-type thermoelectric material is Bio6Sb14Te2ASeo.3S0.325, and the five-element n-type thermoelectric material is the n-type thermoelectric material in Example 1.

It should be understood that the n-type thermoelectric material in Application Examples 1 and 2 may also be selected from the n-type thermoelectric material in Example 2 or 3; x, y, z in the selected p-type thermoelectric material Bi2_,1SbxSjei,i_zSe" may also be selected from the ranges of 1.4sixs1.6, 0.0254s-0.15; 0.025sz0.15.

Experimental Example 'I The thermoelectric conversion rates of the thermoelectric power generation chips according to Application Examples 1-2 of the present disclosure were detected; wherein when the thermoelectric conversion rate was measured, the temperature of the hot surface was 180 'C, and the temperature of the cold surface was 30 "C. The detection results indicate that no-load thermoelectric conversion rates of the thermoelectric power generation chips in Application Examples 1-2 of the present disclosure are 25% and 22%, respectively, and the payload rates are? 7.1%, significantly higher than the thermoelectric conversion rate of the conventional thermoelectric power generation chips existing in the art.

Finally, it should be indicated that the various examples above are merely used for illustrating the technical solutions of the present disclosure, rather than limiting the present disclosure: while the detailed description is made to the present disclosure with reference to various preceding examples, those ordinarily skilled in the art should understand that they still could modify the technical solutions recited in various preceding examples, or make equivalent substitutions to some or all of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the various examples of the present disclosure,

Industrial Applicability

The five-element n-type thermoelectric material provided in the present disclosure and the five-element n-type thermoelectric material made by the preparation method provided in the present disclosure have the advantages of a high Seebeck coefficient; high electrical conductivity and a low thermal conductivity coefficient, thus, they have a high ZT value and excellent thermoelectric properties; and the thermoelectric chips prepared by the five-element thermoelectric material system provided in the present disclosure have good thermoelectric properties and a high thermoelectric conversion rate.

Claims

What is claimed is: 1. A five-element n-type thermoelectric material, characterized in that a chemical formula of the n-type thermoelectric material is Bi2..x.,Sb),S,Te3..7Se7., where 0.74.s.:x.s.:1.2, 0.041:1s:0.06, 0.2rszs0.45.
2, The n-type thermoelectric material according to claim 1, characterized in that the x is 0.74, 0.95 or 1.2, the y is 0.04, 0.05 or 0.06, and the z is 0.2, 0.35 or 0.45.
3. The n-type thermoelectric material according to claim 1, characterized in that bandgap of the n-type thermoelectric material is 0.29-0.31 eV, and preferably; the bandgap of the n-type thermoelectric material is 0.29 eV, 0.30 eV 01 0.31 eV.
4. The n-type thermoelectric material according to claim 1, characterized in that the n-type thermoelectric material has a lattice constant ranging 1.0473-1.0587 rim, and a density ranging 6.8-6.7 gicm3.
5. A five-element thermoelectric material system, characterized in that the thermoelectric material system comprises a five-element p--type thermoelectric material and the five-element n-type thermoelectric material according to any one of claims 1-3, wherein a chemical formula of the five-element p-type thermoelectric material is Bi2.,1Sb,,SyTe:3Se7, where 1.45.xs1.6, 0.02541.50.15, 0.025stzts0.15.
6. A method for preparing the n-type thermoelectric material according to any one of claims 1-4, characterized in that the n-type thermoelectric material is prepared by the method in a manner of realizing powder alloy sintering phase transformation based on crystal topology, wherein the method comprises, mixing, smelting, pulverizing, cold-pressing and sintering elemental powder Bi, Sb, S, Te and Se according to the chemical formula Bi.,a_x_vSbxSvTe3aSez, so as to obtain a molded n-type thermoelectric material; and in the method, the following physical changes happen in a preparation process: forming a p-type alloy by smelting; pulverizing and cold-pressing the p-type alloy to prepare a p-type powder alloy blank; and sintering the p-type powder alloy blank to obtain the five-element n-type thermoelectric material.
7. The method according to claim 6, characterized in that the smelting comprises: smelting mixed elementary substances in a vacuum sealed state, wherein a smelting temperature is 660-680 "C, a smelting duration is 45-48 h, and after finishing the smelting, naturally cooling a resultant to room temperature, to obtain a thermoelectric material alloy ingot; preferably; the smelting temperature is 660 'C, and the smelting duration is 45 h; preferably, a container for smelting the mixed elementary substances is a quartz 35 tube, wherein one end of the quartz tube is sealed, and after the elementary substances are loaded into the quartz tube, the quartz tube is evacuated, and the quartz tube is heated until the quartz tube is sealed by melting, and a sealed quartz tube is used for smelting; more preferably, the quartz tube is heated at a position at least 10 cm from a sample interface formed by the elementary substances in the quartz tube, to form the sealed quartz tube by melting; more preferably, a vacuum degree in the quartz tube is less than 10 pa; and more preferably, the quartz tube is smelted in a heating furnace, for example, a resistance heating furnace.
8. The method according to claim 6 or 7, characterized in that the mixing comprises: adding the elemental powder Bi, Sb, S, To and Se into a vacuum container in proportion, and rotationally mixing the same under a protective atmosphere.
9. The method according to claim 8, characterized in that a rotational speed of the rotational mixing is 30-100 rlmin, and duration is 15-40 h.
10. The method according to claim 8, characterized in that the protective atmosphere is nitrogen or an inert gas.
11. The method according to any one of claims 6-10, characterized in that a purity of the elemental powder Bi, Sb, S, Te and Se is 4 N -5 N.
12. The method according to any one of claims 6-1'1, characterized in that the pulverizing comprises: coarsely pulverizing an alloy obtained by the smelting, and then further crushing the alloy under a protective atmosphere to a particle size of 250-270 meshes, to obtain alloy powder.
13. The method according to claim 12, characterized in that a manner adopted for further crushing the alloy is ball milling.
14. The method according to claim 13, characterized in that a duration of the ball milling is 15-30 h.
15. The method according to any one of claims 6-14, characterized in that the cold-pressing comprises: pressing pulverized alloy powder into a blank in a manner of cold isostatic pressing, for example, by a hydraulic press; and preferably, after the cold isostatic pressing, the blank has a density no less than 96% of that of the molded n-type thermoelectric material.
16. The method according to any one of claims 6-15, characterized in that the sintering comprises: placing a blank into a cavity of a clamp, and then placing the clamp into a sintering furnace for sintering and molding; preferably, a temperature of the blank when being sintered is 60-85% of a temperature when being smelted; preferably, a duration of the sintering is 4-6 h; and preferably, a high-temperature-resistant alloy steel briquetting and aluminum alloy are further placed in the cavity of the damp, wherein the high-temperature-resistant alloy steel briguetting is located between the blank and the aluminum alloy, and in a sintering process, the aluminum alloy compresses the blank through expansion.
17. Use of the five-element thermoelectric material system according to claim 5 in preparation of a thermoelectric chip, preferably, the five-element p-type thermoelectric material and the five-element n--type thermoelectric material are used to prepare a p-n galvanic couple arm in the thermoelectric chip; and more preferably, the thermoelectric chip is a thermoelectric power generation chip or a thermoelectric refrigeration chip.
18. A thermoelectric chip, characterized in that the chip comprises a p-n Galvanic couple arm, wherein the p-n galvanic couple arm is prepared by the five-element thermoelectric material system according to claim 5, and preferably, the thermoelectric chip is a thermoelectric power generation chip or a thermoelectric refrigeration chip.