CN111057884A

CN111057884A - N-type antimony-doped scandium-doped tri-magnesiated antimony alloy thermoelectric material and preparation method thereof

Info

Publication number: CN111057884A
Application number: CN201911190219.1A
Authority: CN
Inventors: 裴艳中; 李文; 史雪敏
Original assignee: Tongji University
Current assignee: Tongji University
Priority date: 2019-11-28
Filing date: 2019-11-28
Publication date: 2020-04-24

Abstract

The invention relates to an N-type antimony-doped scandium alloy thermoelectric material with a chemical formula of Mg and a preparation method thereof_3.05‑xSc_xSb_2‑yBi_yWherein, 0<y≤1,0<x is less than or equal to 0.03. Compared with the prior art, the method improves the doping introduction of scandium by solid solution of the bismuth trimagneside, introduces cation electrons, realizes the simultaneous regulation and control of carrier concentration and lattice thermal conductivity, and utilizes tantalum packaging melting to lead N-type Mg₃Sb₂The content of magnesium oxide in the grain boundary of the alloy is reduced, thereby showing higher mobility, which is simpleThe controllable technology can be widely applied to various thermoelectric materials, particularly to materials with a large number of intrinsic defects, and provides a new method for improving thermoelectric performance.

Description

N-type antimony-doped scandium-doped tri-magnesiated antimony alloy thermoelectric material and preparation method thereof

Technical Field

The invention belongs to the technical field of thermoelectric materials, and relates to an N-type antimony-doped scandium-doped tri-magnesiated thermoelectric material and a preparation method thereof.

Background

The thermoelectric semiconductor material isThe material can directly realize the conversion between heat energy and electric energy, has the advantages of no emission and no need of rotating parts, and is favorable for relieving the energy crisis. The bottleneck limiting the large-scale application of thermoelectric semiconductor materials is their relatively low conversion efficiency, which can be generally measured by a dimensionless thermoelectric figure of merit, zT ═ S²σ T/κ, wherein: t is absolute temperature, S is Seebeck coefficient, σ is electric conductivity, κ is thermal conductivity, and k is heat conductivity from electrons_EAnd lattice thermal conductivity κ_LTwo parts are formed.

Due to Seebeck coefficient S, electric conductivity sigma and electronic thermal conductivity kappa_EThere is a strong coupling relationship between them, which negates the trade-off, making it difficult to achieve high thermoelectric performance by simply optimizing a certain parameter. S, σ and κ_EThe strong coupling between them is most pronounced by the carrier concentration. A high carrier concentration results in a high electrical conductivity but at the same time in a high electronic thermal conductivity and a low seebeck coefficient. However, this coupling can always be used to maximize thermoelectric figure of merit by adjusting the carrier concentration to an optimum value. This allows the carrier concentration to be optimized to be the most common and most effective method for improving thermoelectric performance. The carrier concentration required for optimal electrical performance has temperature and band structure dependence, and a common method for adjusting and controlling the carrier concentration is doping by element replacement. In recent years, thermoelectric Mg₃Sb₂Alloys, particularly N-type conducting alloys, are receiving increasing attention for their application in the thermoelectric field due to their multi-valley conduction band, rich composition and less toxicity. However, the high saturated vapor pressure, corrosiveness and high melting point of magnesium often result in the presence of interfacial phases and defects, thereby affecting the transport properties of the material.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide an N-type antimony tri-magnesium scandium-doped alloy thermoelectric material and a preparation method thereof.

The purpose of the invention can be realized by the following technical scheme:

one of the technical schemes of the invention is to provide an N-type antimony-doped scandium-doped tri-magnesiated alloy thermoelectric material which is characterized in that the chemical formula is Mg_3.05-xSc_xSb_2-yBi_yWherein, 0<y≤1,0<x is less than or equal to 0.03. Because magnesium is active in chemical property and easy to volatilize and oxidize, the excess of magnesium is about 1.7 percent, and because magnesium steam is easy to corrode a quartz tube and the saturated steam pressure is very large, generally, the excess of magnesium is 6.7 percent in the prior document.

Further, y is 0.5 to 1, and x is 0.003 to 0.009.

Furthermore, y is 1, and x is 0.003 to 0.005.

Further, x is 0.002 to 0.005. In this case, the carrier concentration is relatively high, and the average thermoelectric figure of merit is relatively high.

Intrinsic antimony trimagneside has a large number of cation vacancies, resulting in too low a concentration (-10) of its hole carriers¹⁷cm^-3) This is one of the main reasons limiting its thermoelectric performance. Vacancies are thermodynamically equilibrium point defects, with the equilibrium concentration of vacancies being fixed for a given material system at a certain temperature. The bismuth trimagneside with the metal semiconductor characteristic is dissolved in the antimony trimagneside in a solid mode, the forbidden bandwidth is reduced, cation vacancies are introduced, and due to the fact that the cation vacancies with too high concentration enable the material to be unstable thermodynamically, and the scandium dissolution is increased. As the valence balance of the introduced trimagnesized bismuthate does not provide a carrier, the dissolved scandium reduces the vacancy which originally provides the carrier and converts the vacancy into electrons which can provide the carrier, the carrier concentration in the alloy is improved, and meanwhile, the mobility of the alloy is improved through the preparation method, and the electrical property is effectively enhanced. Meanwhile, the point defect scattering caused by a large amount of electrons is enhanced, so that the lattice thermal conductivity of the material is greatly reduced to 0.6W/m-K, and a material with high performance is developedMg of (2)_3.05-xSc_xThe thermoelectric figure of merit of the SbBi novel thermoelectric material reaches 0.8 at 300K, reaches 1.3 at 500K, and reaches 1.13 in the range of 300-plus-500K temperature region, thus being a novel thermoelectric material with large-scale application potential.

Scandium ions are in positive trivalent state, and can add one more electron at the position of magnesium ions by doping, so that an n-type semiconductor is manufactured, compared with the conventional yttrium ions, the scandium ion radius (74.5pm) and the magnesium ion radius (72pm) are closest, so that the doping effect is better, and the room temperature thermoelectric property of the material can be increased from 0.6 to 0.8. Compared with tellurium ions, the cation doping adopted by the invention is far lower than anion doping due to defect forming energy, so that the doping efficiency is higher (the tellurium doping efficiency is about 40 percent, and the scandium doping efficiency is about 80 percent), and higher carrier concentration can be achieved.

The second technical scheme of the invention is to provide a preparation method of an N-type antimony-doped scandium-doped tri-magnesiated thermoelectric material, which comprises the following steps:

(1) and (3) vacuum packaging:

weighing simple substance raw materials Mg, Bi, Sb and Sc according to a stoichiometric ratio, filling the simple substance raw materials into a tantalum tube for vacuum packaging, and then putting the sealed tantalum tube into a quartz tube for vacuum packaging;

(2) melting and quenching:

heating a quartz tube of the tantalum tube filled with the elemental raw materials to enable the raw materials to fully react in a molten state, and quenching to obtain a first ingot;

(3) annealing and quenching:

vacuum packaging the first ingot obtained in the step (2) in a quartz tube again, heating, annealing at high temperature, and then quenching to obtain a second ingot;

(4) hot-pressing and sintering:

and (4) shearing the second cast ingot obtained in the step (3), carrying out vacuum hot-pressing sintering, and then cooling to obtain a flaky block material, namely the target product.

Further, the heating process conditions in the step (2) are as follows: heating the quartz tube from room temperature to 1100-1500 ℃ at the rate of 150-200 ℃ per hour, and preserving the temperature for 4-6 hours to ensure that the simple substance raw materials are fully reacted in a molten state.

Further, the heating in step (2) has the following process conditions: the quartz tube was warmed from room temperature to 1100 ℃ at 200 ℃ per hour and incubated.

Further, the annealing process conditions in the step (3) are as follows: heating the quartz tube from room temperature to 575-625 ℃ at the rate of 150-200 ℃ per hour, and keeping the temperature for 2-4 days.

Furthermore, the annealing process conditions in the step (3) are as follows: the quartz tube was annealed by raising the temperature from room temperature to 600 ℃ at 200 ℃ per hour and maintaining the temperature for 3 days.

Further, the process conditions of the hot pressing sintering in the step (4) are as follows: heating to 550-600 ℃ at the rate of 100-300 ℃ per minute by using induction heating, adjusting the pressure to 90-100 MPa, carrying out constant-temperature and constant-pressure treatment, and carrying out vacuum hot-pressing sintering.

Furthermore, in the step (4), the sintering temperature is 577 ℃, and the sintering pressure is 100 MPa.

Further, the absolute vacuum degree of the vacuum in the step (1), the step (3) and the step (4) is not more than 10^- ¹Pa。

Furthermore, the purity of the simple substance raw materials is more than 99.99 percent.

The invention utilizes the vacuum packaging of the tantalum tube to avoid the loss of magnesium caused by overhigh vapor pressure of magnesium and reduce the enrichment of magnesium oxide at the grain boundary, thereby improving the mobility. More importantly, the inherent high mobility successfully enables thermoelectric performance patterns in the best composition to be compared with commercial N-type Bi₂Te₃The alloy is very competitive and performs better than other known N-type thermoelectric materials at operating temperatures. The invention discloses Mg₃Sb₂Alloys are the first candidate for near-room temperature thermoelectric applications.

Compared with the prior art, the invention has the following advantages:

(1) different from the traditional method of regulating and controlling the carrier concentration by doping the aliovalent atoms, the method has the advantages that the carrier concentration and the mobility of the antimony trimagneside base material are greatly improved to approximate optimization levels by introducing anion electrons and artificially regulating a sintering method and driving through thermodynamic equilibrium conditions.

(2) When the carrier concentration is increased, due to a large number of point defects artificially introduced, the enhancement effect on phonon scattering is obvious, so that the lattice thermal conductivity is greatly reduced (to-0.7W/m-K). The combined effect of the carrier concentration increase and the lattice thermal conductivity reduction enables the thermoelectric figure of merit to reach 0.8 at 300K, 1.3 at 500K and 1.13 at 300-500K. It can be seen that the Mg content is higher than that of conventional pure Mg₃Sb₂Thermoelectric material (pure Mg)₃Sb₂The lattice thermal conductivity of the alloy is 1.4W/m-K, the peak value of thermoelectric figure of merit is-0.2), the invention introduces Mg₃Bi₂And Sc makes Mg₃Sb₂The performance of the thermoelectric material is greatly improved.

(3) The technical scheme provided by the invention has the advantages of simple engineering method and simple used dopant, is favorable for material stability, and can realize fine regulation and control of carrier concentration, mobility and lattice thermal conductivity. The regulation and control method has guiding significance for developing novel high-performance thermoelectric materials.

Drawings

FIG. 1 shows Mg of different compositions_3.05-xSc_xSbBi and Mg_3.05-xSc_xSb_1.5Bi_0.5X-ray diffraction patterns of (a);

FIG. 2 is Mg_3.045Sc_0.005Scanning electron microscope pictures and energy spectra of SbBi (best performing samples);

FIG. 3 is Mg_3.045Sc_0.005Scanning electron microscope pictures of the pressed sheets after SbBi (best performing sample) was corroded with dilute aqueous nitric acid;

FIG. 4 shows Mg of different compositions_3.05-xSc_xA plot of doping percentage of SbBi at 300K versus hall carrier concentration (nH);

FIG. 5 shows Mg of different compositions_3.05-xSc_xHall mobility (. mu.) of SbBi_H) Graph against temperature and comparative graph against literature material;

FIG. 6 shows Mg of different compositions_3.05-xSc_xHall carrier concentration (n) of SbBi_H) Temperature dependence;

FIG. 7 shows Mg of different compositions_3.05-xSc_xSbBi Seebeck coefficient (S) and Hall carrier concentration (n)_H) A relationship diagram of (1);

FIG. 8 shows Mg of different compositions_3.05-xSc_xSbBi Hall mobility (μ)_H) And hall carrier concentration (n)_H) A relationship diagram of (1);

FIG. 9 shows Mg of different compositions_3.05-xSc_xEffective mass of SbBi

And deformation potential coefficient (E)_def) Temperature dependence;

FIG. 10 shows Mg of different compositions_3.05-xSc_xA Seebeck coefficient (S) of SbBi as a function of temperature;

FIG. 11 shows Mg of different compositions_3.05-xSc_xA graph of resistivity (ρ) versus temperature for SbBi;

FIG. 12 shows Mg of different compositions_3.05-xSc_xA graph of total thermal conductivity (κ) of SbBi versus temperature;

FIG. 13 shows Mg of different compositions_3.05-xSc_xLattice thermal conductivity (κ) of SbBi taking into account bipolar effect_L+κ_bip) Temperature dependence;

FIG. 14 Mg of samples of the same composition_3.05-xSc_xA plot of seebeck coefficient (S) of SbBi (x ═ 0.003, 0.005) versus temperature for multiple replicates;

FIG. 15 shows Mg of samples of the same composition_3.05-xSc_xResistivity (ρ) versus temperature for SbBi (x ═ 0.003, 0.005) for multiple replicates;

FIG. 16 Mg of samples of the same composition_3.05-xSc_xGraph of thermoelectric figure of merit zT versus temperature for SbBi (x ═ 0.003, 0.005) for multiple replicates;

FIG. 17 is Mg_3.045Sc_0.005Comparing the average thermoelectric figure of merit of SbBi with other preparation methods and other N-type thermoelectric materials;

FIG. 18 shows Mg of different compositions_3.05-xSc_xSound velocity diagram at room temperature of SbBi;

FIG. 19 shows Mg of different compositions_3.05-xSc_xA relation graph of thermoelectric figure of merit and temperature of SbBi;

FIG. 20 shows Mg of the same composition in different hot pressing directions_3.05-xSc_xA graph of seebeck coefficient (S), resistivity (ρ), total thermal conductivity (κ), and thermoelectric figure of merit zT versus temperature for SbBi (x ═ 0.003, 0.005);

FIG. 21 is Mg_3.05-xSc_xSb_1.5Bi_0.5Hall carrier concentration (n) (x ═ 0.015, 0.03)_H) Hall mobility (μ)_H) Seebeck coefficient (S), resistivity (ρ), total thermal conductivity (κ), and thermoelectric figure of merit zT versus temperature.

Detailed Description

The invention is described in detail below with reference to the figures and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the scope of the present invention is not limited to the following embodiments.

In the following embodiments or specific examples, unless otherwise indicated, all materials or processing techniques are conventional in the art.

One of the technical schemes of the invention is to provide an N-type antimony-doped scandium-doped tri-magnesiated alloy thermoelectric material which is characterized in that the chemical formula is Mg_3.05-xSc_xSb_2-yBi_yWherein, 0<y≤1,0<x≤0.03。

In a specific embodiment of the present invention, y is 0.5 to 1, and x is 0.003 to 0.009. In a more specific embodiment, y is 1, and x is 0.003 to 0.005.

(1) and (3) vacuum packaging:

(2) melting and quenching:

(3) annealing and quenching:

(4) hot-pressing and sintering:

In a specific embodiment of the present invention, the process conditions for heating in step (2) are: heating the quartz tube from room temperature to 1000-1100 ℃ at the rate of 150-200 ℃ per hour, and preserving the temperature for 4-6 hours to ensure that the simple substance raw materials are fully reacted in a molten state. In a more specific embodiment, the process conditions for heating in step (2) are: the quartz tube was warmed from room temperature to 1100 ℃ at 200 ℃ per hour and incubated.

In a specific embodiment of the present invention, the annealing conditions in step (3) are: heating the quartz tube from room temperature to 575-625 ℃ at the rate of 150-200 ℃ per hour, and keeping the temperature for 2-4 days. Furthermore, the annealing process conditions in the step (3) are as follows: the quartz tube was annealed by raising the temperature from room temperature to 600 ℃ at 200 ℃ per hour and maintaining the temperature for 3 days.

In a specific embodiment of the present invention, the process conditions of the hot-pressing sintering in step (4) are as follows: heating to 550-600 ℃ at the rate of 100-300 ℃ per minute by using induction heating, adjusting the pressure to 90-100 MPa, carrying out constant-temperature and constant-pressure treatment, and carrying out vacuum hot-pressing sintering. In a more specific embodiment, in the step (4), the sintering temperature is 577 ℃ and the pressure used for sintering is 100 MPa.

In a specific embodiment of the invention, the absolute vacuum degree of the vacuum in the step (1), the step (3) and the step (4) is not more than 10^-1Pa。

In one embodiment of the present invention, the purity of the elemental feedstock is greater than 99.99%.

The above embodiments may be implemented individually, or in any combination of two or more.

The present invention will be further described with reference to the following more specific examples.

Example 1

A antimony trimagneside thermoelectric material with a chemical formula of Mg_3.05-xSc_xSb_2-yBi_yWherein, 0<x≤0.03,0<y is less than or equal to 1, and in the embodiment, by taking x as 0.001, 0.0015, 0.003, 0.005, 0.009, 0.012, 0.015, 0.020, 0.025, 0.03 and y as 0.5 and 1, namely by changing the concentrations of Sc and Mg₃Bi₂To optimize carrier concentration, mobility and reduce lattice thermal conductivity, Mg with different carrier concentrations was prepared according to the following preparation method_3.05-xSc_xSb_2-yBi_yBulk material:

(1) according to the formula of Mg according to different values of y_3.05-xSc_xSb_2-yBi_yWeighing simple substance raw materials Mg, Bi, Sb and Sc with the purity of more than 99.99% according to the stoichiometric ratio of (y is 0.5-1), putting the simple substance raw materials into a tantalum tube, carrying out vacuum packaging by using an arc melting method, and putting the sealed tantalum tube into a quartz tube and carrying out vacuum packaging.

(2) Suspending the quartz tube containing the raw materials in a high-temperature well type furnace, slowly heating to 1100-1170 ℃ at the rate of 150-200 ℃ per hour, preserving heat for 6-8 hours, and then rapidly quenching and cooling to obtain a first ingot; this step of this example was selected to be slowly ramped up to 1150 ℃ at a rate of 200 ℃ per hour and held at 1150 ℃ for 7 hours.

(3) Carrying out heat treatment on the first ingot subjected to high-temperature melting quenching obtained in the step (2), slowly heating to 575-625 ℃ at the rate of 150-200 ℃ per hour, preserving heat for 2-4 days, and then rapidly quenching and cooling to obtain a second ingot; this step of this example was performed by slowly raising the temperature to 600 ℃ at a rate of 200 ℃ per hour and holding the temperature for 3 days.

(4) Shearing the second cast ingot obtained in the step (3) into 2mm fragments, placing the fragments in a graphite mold, heating to 500-600 ℃ at the rate of 100-300 ℃ per minute by using induction heating, adjusting the pressure to 70-100 MPa, keeping the temperature for 15 minutes, performing vacuum high-temperature hot-pressing sintering, and slowly cooling to room temperature at the rate of 20-30K/min to obtain Mg_3.05-xSc_xSb_2-yBi_yThe flaky block material is the antimony trismagnesium alloy thermoelectric material; in the step of this embodiment, the temperature is raised to 577 ℃ at a rate of 200 ℃ per minute, the pressure is adjusted to 100MPa, the temperature is kept for 25 minutes, vacuum high-temperature hot-pressing sintering is performed, and then the material is slowly cooled to room temperature at a rate of 25K/min.

Mg prepared in this example_3.05-xSc_xSb_2-yBi_yAn X-ray diffraction pattern of (X ═ 0.001, 0.0015, 0.003, 0.005, 0.009, 0.012, 0.015, 0.020, 0.025, 0.03, and y ═ 0.5 and 1.0) is shown in fig. 1. The antimony trimagneside alloy prepared by the tantalum tube packaging melting mode basically has no impurity phase precipitation. As shown in fig. 2, the scanning electron microscope and the energy spectrum picture further confirm that the material obtained by the preparation method is the antimony trismagnesium alloy material without impurities.

Mg of different composition_3.05-xSc_xSb_2-yBi_yThe relationship (Pisarenko) of the seebeck coefficient (S) with the hall carrier concentration at room temperature is shown in fig. 7. All samples are in good accordance with the Pisarenko curve of the single parabolic zone model, and the influence on the energy band of the material is very weak when the solid solubility of the bismuth trimagneside is 25-50%.

Mg of different composition_3.05-xSc_xSb_2-yBi_yHall mobility (μ) at room temperature_H) The relationship with hall carrier concentration (Pisarenko) is shown in fig. 8, which graphically shows that as the solid solubility of bismuthyl trimagneside increases from 25% to 50%, the hall mobility of the material also increases, indicating that trimagnesium is enhancedThe improvement of the solid solubility of the bismuth oxide is beneficial to improving the electrical property of the material.

Further, as shown in fig. 13 and 21(c), as the solid solubility of bismuth trimagneside increases, a further decrease in lattice thermal conductivity may be obtained due to the introduction of additional acoustic phonon scattering. Finally, Mg at different solid solubilities were compared_3.05-xSc_xSb_2-yBi_yThe thermoelectric figure of merit ZT of the thermoelectric property is measured, and the effect of 50% solid solution of bismuth trimagneside on improving the thermoelectric property is more obvious.

Therefore, the working selection further optimizes thermoelectric performance on the basis of 50% of solid solution bismuth trimagneside. Prepared Mg_3.045Sc_0.005Scanning electron microscopy of SbBi (best performing sample) ingots (fig. 2) and of tablets after etching with dilute aqueous nitric acid (fig. 3). Verify Mg_3.05-xSc_xCompared with the literature, the crystal grain size of the antimony trimagneside alloy prepared by using the tantalum tube packaging melting mode in SbBi is one of the largest, so that the thermoelectric performance is improved. The relevant references are as follows: (1) kanno, t.; tamaki, h.; sato, h.k.; kang, s.d.; ohno, s.; imasato, k.; kuo, j.j.; snyder, g.j.; miyazaki, y.appl.phys.lett.2018, (3),033903.(2) Imasato, k.; kang, s.d.; snyder, G.J., Energ Environ Sci 2019, DOI 10.1039/C8EE03374A (3) Shi, X.; sun, c.; bu, z.; zhang, x.; wu, y.; lin, s.; li, W.; faghaninia, A.; jain, A.; pei, y., Advanced science 2019,6, (16),1802286.

FIG. 4 shows Mg of different compositions_3.05-xSc_xDoping percentage and Hall carrier concentration (n) of SbBi at 300K_H) According to the relation graph, the doping efficiency of scandium is about 80%, is much higher than that of anion doping, and is similar to that of cation lanthanum.

FIG. 5 shows Mg of different compositions_3.05-xSc_xHall mobility (. mu.) of SbBi_H) The mobility of the magnesium antimonide material prepared by the tantalum tube packaging and high-pressure sintering mode accords with acoustic phonon scattering.

FIG. 6 shows a differenceMg of composition (I)_3.05-xSc_xHall carrier concentration (n) of SbBi_H) With respect to temperature, it can be seen that as the doping content of scandium increases, the carrier concentration increases, indicating effective doping of scandium, and that the carrier concentration is substantially constant with temperature, indicating thermal stability of the material over the test temperature range.

As the carrier concentration is driven to rise by artificially introducing cation electrons, the Seebeck coefficient and the resistivity of the material gradually decrease along with the increase of x, and the total thermal conductivity decreases. When x reaches 0.003 to 0.005, the performance in the vicinity of room temperature is optimized. FIG. 10, FIG. 11 and FIG. 12 are Mg, respectively_3.05-xSc_xAnd the SbBi seebeck coefficient, the resistivity and the total thermal conductivity are plotted along with the temperature change. It can be seen that the thermoelectric figure of merit of the alloy is optimized when x reaches 0.003 and 0.005 (FIG. 19).

FIG. 9 shows Mg of different compositions_3.05-xSc_xDeformation potential constant (E) of SbBi_def) And density of states effective mass (m ×)_DOS) Graphical representation of the change in temperature, the deformation potential constant (E) can be found_def) And density of states effective mass (m ×)_DOS) The change is not obvious in the whole testing temperature range, which shows that the material is stable and has no obvious energy band change.

FIG. 18 shows Mg of different compositions_3.05-xSc_xThe sound velocity of SbBi changes along with the doping of Sc, and the sound velocity is basically kept unchanged along with the change of the doping amount, so that the influence of a small amount of doping on the sound velocity and the thermal conductivity of crystal lattices is eliminated.

FIG. 17 is Mg_3.045Sc_0.005The average thermoelectric figure of merit of SbBi is as high as 1.13(300K-500K) compared with other preparation methods and other N-type thermoelectric materials, and as can be seen from the figure, the high mobility successfully enables the thermoelectric performance in the best composition to exceed that of all N-type thermoelectric materials including bismuth telluride in the working temperature range, and the study reveals that Mg₃Sb₂Alloys are the material of choice for near-room temperature thermoelectric applications.

FIGS. 14, 15 and 16 show the two samples Mg that perform best for example 1_3.05-xSc_xSbBi(x0.003, 0.005) can be repeatedly tested to obtain stable and similar data, which indicates that the sample has stable thermoelectric performance and is beneficial to commercial repeated use.

Mg having the same composition but different hot pressing directions, prepared in the above examples_3.05-xSc_xAs shown in fig. 20, the resistivity (ρ) of SbBi (x ═ 0.003, 0.005), seebeck coefficient (S), total thermal conductivity (κ), and thermoelectric figure of merit zT vary with temperature, and it can be seen that the material has weak anisotropy and is substantially isotropic.

Mg of different composition_3.05-xSc_xSb_1.5Bi_0.5(x ═ 0.015, 0.03) resistivity (ρ), seebeck coefficient (S), total thermal conductivity (κ), and thermoelectric figure of merit zT as a function of temperature are shown in fig. 21 as Mg₃Bi₂In comparison with the sample material with the solid solution amount of 50%, it can be seen that the thermoelectric performance of the material is better when the solid solution amount is 50%.

Example 2

Most of them were the same as in example 1 except that in this example, the sintering temperature in step (4) was 550 ℃ and the pressure used for sintering was 100 MPa.

Example 3

Compared with example 1, the same is most true except that in this example, the sintering temperature in step (4) is 650 ℃ and the sintering pressure is 100 MPa.

Example 4

Compared with the embodiment 1, the method is mostly the same, except that in the step (4) of the embodiment, the temperature is increased to 600 ℃ at the rate of 300 ℃ per minute, the pressure is adjusted to 100MPa, the temperature is kept for 20 minutes, the vacuum high-temperature hot-pressing sintering is carried out, and then the temperature is slowly cooled to the room temperature at the rate of 30K/min.

Example 5

Compared to example 1, most of them are the same except that in this example, in step (2), the temperature is slowly raised to 1100 ℃ at a rate of 150 ℃ per hour and maintained for 6 hours.

Example 6

Most of the same is compared to example 1, except that in this example, in step (2), the temperature is slowly raised to 1500 ℃ at a rate of 175 ℃ per hour and held for 8 hours.

Example 7

Compared with example 1, most of them are the same except that in the step (3), the temperature is slowly raised to 575 ℃ at the rate of 150 ℃ per hour, and the temperature is maintained for 4 days.

Example 8

Most of them were the same as in example 1, except that in this example, in step (3), the temperature was slowly raised to 625 ℃ at a rate of 175 ℃ per hour, and the temperature was maintained for 2 days.

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

Claims

1. An N-type antimony-doped scandium-doped tri-magnesiate thermoelectric material, which is characterized in that the chemical formula is Mg_3.05-xSc_xSb_2-yBi_yWherein, 0<y≤1,0<x≤0.03。

2. The N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 1, wherein y is 0.5 to 1 and x is 0.003 to 0.009.

3. The N-type antimony-doped scandium thermoelectric material as claimed in claim 2, wherein y is 1 and x is 0.003-0.005.

4. The method for preparing an N-type antimony tri-magnesium scandium-doped alloy thermoelectric material as claimed in any one of claims 1 to 3, comprising the steps of:

(1) and (3) vacuum packaging:

(2) melting and quenching:

(3) annealing and quenching:

(4) hot-pressing and sintering:

5. The method for preparing the N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 4, wherein the heating in the step (2) is carried out under the following process conditions: heating the quartz tube from room temperature to 1100-1500 ℃ at the rate of 150-200 ℃ per hour, and preserving the temperature for 4-6 hours to ensure that the simple substance raw materials are fully reacted in a molten state.

6. The method for preparing an N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 5, wherein the heating in the step (2) is performed under the following process conditions: the quartz tube was warmed from room temperature to 1100 ℃ at 200 ℃ per hour and incubated.

7. The method for preparing the N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 4, wherein the annealing in the step (3) is carried out under the following process conditions: heating the quartz tube from room temperature to 575-625 ℃ at the rate of 150-200 ℃ per hour, and keeping the temperature for 2-4 days.

8. The method for preparing an N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 7, wherein the annealing in the step (3) is performed under the following process conditions: the quartz tube was annealed by raising the temperature from room temperature to 600 ℃ at 200 ℃ per hour and maintaining the temperature for 3 days.

9. The method for preparing an N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 4, wherein the process conditions of the hot-pressing sintering in the step (4) are as follows: heating to 550-600 ℃ at the rate of 100-300 ℃ per minute by using induction heating, adjusting the pressure to 90-100 MPa, carrying out constant-temperature and constant-pressure treatment, and carrying out vacuum hot-pressing sintering.

10. The method for preparing an N-type antimony-doped scandium alloy tri-magnesiate thermoelectric material as claimed in claim 9, wherein in the step (4), the sintering temperature is 577 ℃ and the sintering pressure is 100 MPa.