CN109671840B - Antimony tellurium selenium matrix alloy construction method for thermoelectric material and antimony tellurium selenium matrix thermoelectric material - Google Patents

Antimony tellurium selenium matrix alloy construction method for thermoelectric material and antimony tellurium selenium matrix thermoelectric material Download PDF

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CN109671840B
CN109671840B CN201811517348.2A CN201811517348A CN109671840B CN 109671840 B CN109671840 B CN 109671840B CN 201811517348 A CN201811517348 A CN 201811517348A CN 109671840 B CN109671840 B CN 109671840B
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朱铁军
李贝贝
翟仁爽
赵新兵
吴勇军
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Zhejiang University ZJU
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    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
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Abstract

The invention discloses a thermoelectric deviceThe method for constructing the antimony tellurium selenium matrix alloy comprises the following steps: chemical formula Sb for constructing matrix alloy2Te3‑xSexWherein x is more than or equal to 0 and less than or equal to 3, calculating the energy band structure of the matrix alloy according to the first principle, selecting the matrix alloy with the highest degeneracy through the energy band structure, and taking the corresponding chemical formula as Sb2Te3‑x′Sex′Wherein x' is more than or equal to 0 and less than or equal to 3; preparation of Sb by zone melting method2Te3‑x″Sex″The value of x 'is x' -0.5-x 'and x' + 0.7; base alloy Sb prepared by testing2Te3‑x″Sex″Further determining the matrix alloy with the highest degeneracy as the matrix alloy for preparing the antimony tellurium selenium-based thermoelectric material. The invention also discloses an antimony tellurium selenium-based thermoelectric material which comprises a matrix alloy Sb2TeSe2And a doping agent M, wherein M is selected from one or a combination of at least two of Ag, Cu, Sn and Pb; sb represents the Sb of Te-Se based thermoelectric material2‑yMyTeSe2Wherein y is more than or equal to 0.8 and less than or equal to 1.965. The antimony tellurium selenium-based thermoelectric material provided by the invention has the optimal thermoelectric figure of merit of at least 0.4 within the temperature range of 500-800K, and is improved by at least 100% compared with antimony tellurium selenium-based alloy.

Description

Antimony tellurium selenium matrix alloy construction method for thermoelectric material and antimony tellurium selenium matrix thermoelectric material
Technical Field
The invention belongs to the field of semiconductor thermoelectric materials, and particularly relates to a construction method of an antimony tellurium selenium matrix alloy for a thermoelectric material and the antimony tellurium selenium based thermoelectric material.
Background
With rapid development of science and technology and economy in the world, global energy demand is continuously increasing. Solving the contradiction between energy supply and demand, and realizing sustainable development is the development direction of the human society at the present stage. The thermoelectric material realizes the mutual conversion between heat energy and electric energy through the transportation and the interaction of current carriers and phonons. The device made of thermoelectric material has the advantages of small volume, no noise, no pollution, simple structure and the like, and has important application prospect in thermoelectric refrigeration and waste heat power generation.
The choice of thermoelectric materials can be divided into three categories depending on their operating temperature:
(1) bismuth telluride and alloys thereof: this is a material that is widely used in thermoelectric coolers at their optimum operating temperature<Lead telluride and its alloys at 450 ℃, (2) which are widely used in thermoelectric generators with an optimum operating temperature of about 1000 ℃, (3) silicon germanium alloys, which are also commonly used in thermoelectric generators with an optimum operating temperature of about 1300 ℃, (500K-900K) most of the waste heat sources are generally in the medium temperature region, and thus, the study of the medium temperature thermoelectric materials is particularly important2σ/(κe+κl) T, wherein α, σ, κeAnd kappalAnd the Seebeck coefficient, the electrical conductivity, the carrier thermal conductivity and the lattice thermal conductivity are respectively, and T is the service temperature of the material.
There are generally two ways to increase the zT of thermoelectric materials, one is to increase their power factor (α)2Sigma), or reduce its thermal conductivity (k), the physical mechanisms that influence power factor include four items, scattering parameters, energy state density, carrier mobility, and fermi level, the main method to experimentally improve power factor is to adjust the fermi level by changing the doping concentration to reach the maximum α2The value of sigma. The thermal conductivity (k) of solid material includes the thermal conductivity (k) of crystal latticeL) And electron thermal conductivity (κ)e) I.e. k ═ kL+κe. The thermal conduction of the thermoelectric material is mostly conducted through the crystal lattice. Lattice thermal conductivity (κ)L) Proportional to the specific heat capacity (C) of the sampleV) Three physical quantities, namely, the speed of sound and the mean free path. At present, phonon engineering is a main way for improving the thermal performance of materials, and is mainly realized by means of introducing a multi-scale micro-nano structure, reducing the grain size of the materials so as to increase grain boundary scattering and the like.
In the field of thermoelectricity, oriented polycrystal is prepared mainly by a zone melting method, polycrystal is prepared by smelting, ball milling and sintering molding (SPS or HP), and materials obtained by the two preparation methods have different characteristics. The material obtained by the zone melting method has stronger texture, and is beneficial to the anisotropic material to obtain good electrical property. However, the oriented polycrystal prepared by the zone-melting method has higher lattice thermal conductivity, thereby limiting further improvement of thermoelectric performance. The powder metallurgy method can introduce a large amount of crystal boundaries, effectively scatter phonons, and reduce lattice thermal conductivity, thereby improving the thermoelectric figure of merit of the material. But the smelting-ball milling-sintering molding (SPS or HP) method has higher preparation cost, so that the method cannot be industrially produced in large scale and stays in the laboratory research stage all the time.
Disclosure of Invention
The invention aims to provide a method for constructing an antimony tellurium selenium matrix alloy for thermoelectric materials, which optimizes the matrix alloy and provides the antimony tellurium selenium matrix alloy with higher degeneracy for preparing the thermoelectric materials; the invention also provides an antimony tellurium selenium-based thermoelectric material, the optimal value of the thermoelectric figure of merit of the antimony tellurium selenium-based thermoelectric material in the temperature range of 500-800K is at least 0.4, the thermoelectric figure of merit is at least 100 percent higher than that of the antimony tellurium selenium-based alloy, and the antimony tellurium selenium-based thermoelectric material is suitable for being used as a thermoelectric material in a medium-temperature region.
A method for constructing an antimony tellurium selenium matrix alloy for thermoelectric materials comprises the following steps:
(1) chemical formula Sb for constructing matrix alloy2Te3-xSexWherein x is more than or equal to 0 and less than or equal to 3, calculating the energy band structure of the matrix alloy through a first principle, selecting the matrix alloy with the highest degeneracy through the energy band structure, and the corresponding chemical formula is Sb2Te3-x′Sex′Wherein x' is more than or equal to 0 and less than or equal to 3;
(2) preparation of Sb by zone melting2Te3-x″Sex″The value of x 'is x' -0.5-x 'and x' +0.7, and the prepared base alloy Sb2Te3-x″Sex″The matrix alloy with the highest degeneracy is selected as the matrix alloy for preparing the antimony tellurium selenium-based thermoelectric material.
In the step (1), the principal theoretical basis of theoretical calculation of the first principle is the fundamental equation and relativistic effect of quantum mechanics, the actual system formed by polyatomic atoms is understood to be a multi-particle system formed by electrons and atoms, and the problem is subjected to non-empirical processing to the greatest extent by applying the basic physical principles such as quantum mechanics. Three approximations are applied in the calculation of the first principle: a non-relativistic approximation; a Born-Oppenheimer approximation, a kernel-fixed approximation; single electron approximation. Can be calculated by Materials Studio, including: model construction, energy calculation and analysis, and energy band calculation and analysis.
In step (2), Sb is produced by a float zone method2Te3-x″Sex″The value of x ' is x ' -0.5-x ' and x ' +0.7, including the base alloy with the highest degeneracy and the base alloy with the value near x ';
in step (1), the matrix alloy with the highest degree of degeneracy selected by the band structure is Sb2TeSe2(ii) a In step (2), the base alloy Sb2Te3-x″Sex″Wherein the value of x' is more than or equal to 1.5 and less than or equal to 2.7.
In the step (2), Sb is selected as the base alloy with the highest degeneracy2TeSe2。
The step (1) is theoretical calculation, the crystal structure of the antimony tellurium selenium alloy based thermoelectric material belongs to a rhombohedral crystal system, the space group is R-3m, and tellurium selenium based series alloy (Sb) is calculated2TeSe2) Has higher degeneracy, and is beneficial to improving the electrical property. However, the theoretical calculation value and the actual calculation value are different, so that the base alloy with the highest degeneracy is finally determined by preparing the thermoelectric properties of the base alloy corresponding to the theoretical calculation value and the values near the theoretical calculation value. In the present invention, the theoretical value is the same as the actual value, and is Sb2TeSe2。
The performance of the thermoelectric material can be optimized by: the degeneracy of the matrix alloy is improved, and the carrier concentration is improved. The invention further improves the thermoelectric property by constructing a matrix alloy with higher degeneracy and adjusting the concentration of current carriers by doping agents.
The band engineering can effectively improve the electrical transport property of the material, and mainly comprises the steps of introducing a resonance energy level, converging an energy band, increasing a band gap and the like. When the energy difference between the energy bands and kBWhen T is equal, the energy band converges, resulting in degeneracy (N)v) Is increased. When the inter-valley scattering is weakThe carrier mobility is not lost.
Figure BDA0001902332960000041
Figure BDA0001902332960000042
As can be seen from the above formula, the degree of band degeneracy (N)v) The larger the number of valleys involved in transport, the greater the density of states, the greater the effective mass m, and consequently the greater the seebeck coefficient α2TeSe2And a doping agent M, wherein M is selected from one or a combination of at least two of Ag, Cu, Sn and Pb; the Sb, Te and Se-based thermoelectric material is expressed as Sb2-yMyTeSe2Wherein y is more than or equal to 0.8 and less than or equal to 1.965.
The antimony tellurium selenium-based thermoelectric material provided by the invention is of a P type.
Thermoelectric parameters (α, sigma, kappa) determining thermoelectric properties of the materialeAnd kappal) Are coupled to each other by the carrier concentration of the material. Too low or too high a carrier concentration may deteriorate the material properties. Optimizing the carrier concentration of a material is one of the most important means to adjust thermoelectric performance. Carrier concentration modulation is typically optimized by doping to introduce charged extrinsic point defects. The doped atoms can occupy lattice positions after entering the lattice to form replacement type defects; or occupy van der waals bond gaps, forming gap-type defects. Therefore, the carrier concentration of the base alloy can be adjusted to be theoretically optimal by the doping agent, thereby improving the thermoelectric performance of the base alloy.
Ag. Cu, Sn and Pb are oftenThe compound is used as a doping agent for thermoelectric semiconductor materials, and can effectively improve the carrier concentration. With different dopants, different carrier concentrations are obtained, which are related to the solid solubility and ionization energy of the dopant atoms in the material. For the base alloy Sb2TeSe2The calculated theoretical optimum carrier concentration is 1.0 × 1020-2.0×1020。
Preferably, the doping agent is Sn, and the antimony tellurium selenium-based thermoelectric material is Sb2-nSnnTeSe2Wherein n is more than or equal to 0.08 and less than or equal to 0.12. Sn is commonly used as a doping agent for antimony tellurium selenium congeneric solid solution alloy, and the carrier concentration can be effectively optimized. This range is chosen in order to adjust the carrier concentration to a theoretical optimum.
Preferably, the doping agent is Ag, and the antimony tellurium selenium-based thermoelectric material is Sb2-yAgyTeSe2Wherein y is more than or equal to 0.005 and less than or equal to 0.03. The Ag has smaller atomic radius and higher doping efficiency, and can effectively improve the hole concentration. The number of carriers provided by Ag can be calculated theoretically, and the range is selected in order to adjust the carrier concentration to reach a theoretical optimal value.
The thermoelectric figure of merit of the P-type antimony tellurium selenium-based thermoelectric material is improved by 20 percent to the maximum extent near 750K.
More preferably, the antimony tellurium selenium-based thermoelectric material is Sb2-yAgyTeSe2Wherein y is more than or equal to 0.02 and less than or equal to 0.03. Under the doping concentration range, Ag doping reaches a solid solution limit, carrier concentration as much as possible is provided, and the prepared antimony tellurium selenium-based thermoelectric material has excellent thermoelectric performance.
More preferably, the doping agent is Ag and Cu, and the antimony tellurium selenium-based thermoelectric material is Sb1.98-zAg0.02CuzTeSe2Wherein z is more than or equal to 0.005 and less than or equal to 0.015. And on the basis that the single-doped Ag reaches the solid solution limit, Cu doping is carried out on the basis of Ag in order to further improve the carrier concentration. This range is chosen in order to adjust the carrier concentration to a theoretical optimum.
More preferably, the doping agent is Ag and Pb, and the antimony tellurium selenium-based thermoelectric material is Sb1.98-mAg0.02PbmTeSe2Wherein m is more than or equal to 0.005 and less than or equal to 0.015. And on the basis that the single-doped Ag reaches the solid solution limit, Pb doping is carried out on the basis of Ag in order to further improve the carrier concentration. This range is chosen in order to adjust the carrier concentration to a theoretical optimum.
The thermoelectric figure of merit of the antimony tellurium selenium-based thermoelectric material is at least 0.4 within the temperature range of 500-800K, and is at least 100% higher than that of the antimony tellurium selenium-based alloy.
The preparation method of the antimony tellurium selenium matrix alloy provided by the invention comprises the following steps:
(1) crushing Sb blocks, Te blocks and Se blocks;
(2) according to the chemical formula Sb2Te3-xSexWeighing the raw materials in the step (1) according to the stoichiometric ratio of each element, wherein x is more than or equal to 1.5 and less than or equal to 2.7, and filling the raw materials into a cleaned quartz tube;
(3) pumping the vacuum degree of the quartz tube in the step (2) to be less than or equal to 10-3After Pa, burning the quartz tube wall by oxyhydrogen flame, and sealing the quartz tube wall;
(4) placing the sealed quartz tube in a rotary smelting furnace to be smelted for 10-12 h to obtain a polycrystalline ingot;
(5) and (4) placing the polycrystalline ingot obtained in the step (4) into a vertical zone melting furnace for zone melting growth, and cutting the polycrystalline ingot after preparing the oriented polycrystalline ingot to obtain the P-type antimony tellurium selenium matrix alloy.
The washing process of the quartz tube in the step (2) comprises the following steps: pouring a dilute nitric acid solution (65% nitric acid: water: 1) into a quartz tube, ultrasonically oscillating for 15-20 min, cleaning with clear water, cleaning with absolute ethyl alcohol, and drying the quartz tube.
The smelting temperature in the step (4) is 750-850 ℃.
The conditions of zone-melting growth in the step (5) are as follows: the zone melting temperature is 600-700 ℃, the growth speed is 8-10 mm/h, the temperature gradient of the solid-liquid surface is 25-40K/cm, and the width of the melting zone is 2-3 cm.
The method of the antimony tellurium selenium based thermoelectric material provided by the invention comprises the following steps: adding a doping agent in the step (2).
The antimony tellurium selenium base P-type thermoelectric material provided by the invention obtains a matrix alloy with higher degeneracy through calculation and experimental verification, and provides a new idea for the performance optimization of the thermoelectric material; the carrier concentration is adjusted, so that the medium-temperature section has excellent performance and can be applied to medium-temperature waste heat power generation; the preparation method provided by the invention adopts a zone melting method, has low cost and can be directly applied in commercialization.
Drawings
FIG. 1 is a band calculation chart of an antimony tellurium selenium matrix alloy prepared in example 1;
FIG. 2 is a flow chart of a method for preparing an antimony tellurium selenium-based thermoelectric material provided by the present invention;
FIG. 3 is a graph showing the Seebeck coefficient of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature;
FIG. 4 is a graph of the electrical conductivity of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature;
FIG. 5 is a graph of the power factor of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature;
FIG. 6 is a graph of the thermal conductivity of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature;
FIG. 7 is a graph of thermoelectric figure of merit as a function of temperature for the antimony tellurium selenium matrix alloy prepared in example 1;
FIG. 8 is a graph of the thermoelectric figure of merit of the antimony tellurium selenium based P-type thermoelectric material containing Ag dopant prepared in example 2 as a function of temperature;
FIG. 9 is a graph showing the thermoelectric figure of merit of the Sb-Te-Se-based P-type thermoelectric material containing Ag, Cu and Pb as dopants, as a function of temperature, prepared in example 3;
FIG. 10 is a graph of the thermoelectric figure of merit of the Sb-Te-Se-based P-type thermoelectric material containing Sn dopant prepared in example 4 as a function of temperature.
Detailed Description
In order to better understand the present invention, the following examples are further provided to illustrate the content of the present invention, but the content of the present invention is not limited to the following examples.
Example 1
(1) Crushing Sb blocks, Te blocks and Se blocks with commercial purity of 5N;
(2) pouring a dilute nitric acid solution into a quartz tube with one end sealed and the inner diameter of about 12mm, ultrasonically cleaning for 15-20 min, then cleaning twice with clear water and once with absolute ethyl alcohol, and then putting the quartz tube into an oven to dry for 8h at 100 ℃;
(3) according to the chemical formula Sb2Te3-xSexWeighing 80g of the raw materials in the step (1) according to the stoichiometric ratio of the elements, and putting the raw materials into a dried quartz tube, wherein x is 1.5, 1.8, 1.9, 2.0, 2.1, 2.4 and 2.7;
(4) pumping the vacuum degree of the quartz tube in the step (3) to 10-3Pa, and sealing the other end of the quartz tube by using oxyhydrogen flame;
(5) putting the quartz tube obtained in the step (4) into a rotary smelting furnace at 800 ℃ to be smelted for 10 hours, rotating all the time in the smelting process to ensure that the raw materials are fully mixed, and cooling to room temperature to obtain a polycrystalline ingot;
(6) and (5) placing the polycrystalline ingot obtained in the step (5) on a vertical zone melting furnace for zone melting growth, wherein the zone melting temperature is 600 ℃, the growth speed is 8mm/h, and after zone melting from beginning to end, cooling to room temperature to obtain the oriented polycrystalline ingot.
(7) And cutting one end of the quartz tube filled with the oriented single crystal ingot, pouring out the oriented single crystal ingot, and cutting off the tip part of the oriented single crystal ingot by using linear cutting to obtain the antimony tellurium selenium base p-type thermoelectric semiconductor crystal bar ingot with the length of about 70mm and uniform and stable performance.
Fig. 1 is an energy band diagram of the antimony tellurium selenium matrix alloy when x is 1, x is 2, and x is 0, and it can be seen from fig. 1 that the degeneracy of the antimony tellurium selenium matrix alloy is the highest when x is 2; the dotted line in fig. 1 represents the assumed fermi level, and it can be seen in fig. 1 that the top of the four valence bands is cut when x is 2. When the fermi level cuts more energy band tops at the same time, more energy bands participating in transportation at the same time, namely the degeneracy is higher.
In fig. 3 to 7, x ═ 1.5, 1.8, 1.9, 2.0, 2.1, 2.4, and 2.7 represent the antimony tellurium selenium based P-type thermoelectric materials in the present example, where x ═ 1.5, 1.8, 1.9, 2.0, 2.1, 2.4, and 2.7.
FIG. 3 shows the conductivity response of Sb-Te-Se matrix alloy prepared in example 1Graph of temperature change. FIG. 4 is a graph of the Seebeck coefficient of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature. The seebeck coefficient of the material increases and then decreases with increasing temperature, with a distinct peak around 500K due to band degeneracy. FIG. 5 is a graph of the power factor of the Sb-Te-Se matrix alloy prepared in example 1 as a function of temperature. Fig. 6 is a graph of the thermal conductivity of the antimony tellurium selenium matrix alloy prepared in example 1 as a function of temperature. Fig. 7 is a graph showing the thermoelectric figure of merit of the Sb-te-Se matrix alloy prepared in this example as a function of temperature, and it can be seen from the graph that as the Se content in the material increases, the zT value increases first and then decreases, and when x is 2, the prepared material Sb is Sb2TeSe2The zT value is about 0.2 at 500K to 600K. Namely Sb is further determined as the matrix alloy with the highest degeneracy2TeSe2。
When x is 2.4 in this example, Sb, a material is obtained2Te0.6Se2.4As shown in fig. 7, the zT value of 500K to 600K is only about 0.1, which is mainly due to the fact that the thermoelectric performance of the material is deteriorated by severe intrinsic excitation caused by extremely low carrier concentration; and the component is prepared with obvious impurity phase, thus deteriorating thermoelectric performance.
In this example, when x is 2, the obtained material Sb was prepared2TeSe2The carrier concentration is at a lower level, and the theoretical optimal carrier concentration obtained by calculation is (1.5 multiplied by 10)20) (ii) a The thermal conductivity is 1.25Wm at 500K-1K-1This is due to the higher thermal conductivity of the materials obtained by the zone-melting process; in conclusion, there is still room for improvement in the properties of the composition.
Example 2
As shown in fig. 2, the preparation method of the antimony tellurium selenium-based thermoelectric material is as follows:
(1) crushing Sb blocks, Ag blocks, Te blocks and Se blocks with commercial purity of 5N;
(2) pouring a dilute nitric acid solution into a quartz tube with one end sealed and the inner diameter of about 12mm, ultrasonically cleaning for 15-20 min, then cleaning twice with clear water and once with absolute ethyl alcohol, and then putting the quartz tube into an oven to dry for 8h at 100 ℃;
(3) adding a doping agent Ag according to the chemical formula Sb2-yAgyTeSe2Weighing 80g of the raw materials in the step (1) according to the stoichiometric ratio of the elements, and placing the raw materials in a dried quartz tube, wherein y is 0.005-0.03;
(4) pumping the vacuum degree of the quartz tube in the step (3) to 10-3Pa, and sealing the other end of the quartz tube by using oxyhydrogen flame;
(5) putting the quartz tube obtained in the step (4) into a rotary smelting furnace at 800 ℃ to be smelted for 10 hours, rotating all the time in the smelting process to ensure that the raw materials are fully mixed, and cooling to room temperature to obtain a polycrystalline ingot;
(6) and (5) placing the polycrystalline ingot obtained in the step (5) on a vertical zone melting furnace for zone melting growth, wherein the zone melting temperature is 600 ℃, the growth speed is 8mm/h, and after zone melting from beginning to end, cooling to room temperature to obtain the oriented polycrystalline ingot.
(7) And cutting one end of the quartz tube filled with the oriented single crystal ingot, pouring out the oriented single crystal ingot, and cutting off the tip part of the oriented single crystal ingot by using linear cutting to obtain the antimony tellurium selenium base p-type thermoelectric semiconductor crystal bar ingot with the length of about 70mm and uniform and stable performance.
Fig. 8 is a graph of the thermoelectric figure of merit of the P-type sb-te-se based thermoelectric material prepared in this example as a function of temperature, and when y is 0.02, the thermoelectric figure of merit of the novel P-type sb-te-se based thermoelectric material prepared in this example is improved by 100% due to the existence of band degeneracy and further optimization of carrier concentration, and the zT value around 700K to 800K is about 0.4.
Example 3
(1) Crushing Sb blocks, Ag blocks, Pb blocks, Cu blocks, Te blocks and Se blocks with commercial purity of 5N;
(2) pouring a dilute nitric acid solution into a quartz tube with one end sealed and the inner diameter of about 12mm, ultrasonically cleaning for 15-20 min, then cleaning twice with clear water and once with absolute ethyl alcohol, and then putting the quartz tube into an oven to dry for 8h at 100 ℃;
(3) adding Ag block, Pb block, Cu block, and Sb1.98-zAg0.02CuzTeSe2、Sb1.98- mAg0.02PbmTeSe2Weighing 80g of the raw materials in the step (1) according to the stoichiometric ratio of the elements, and placing the raw materials in a dried quartz tube, wherein z is 0.005-0.015, and m is 0.005-0.015;
(4) pumping the vacuum degree of the quartz tube in the step (3) to 10-3Pa, and sealing the other end of the quartz tube by using oxyhydrogen flame;
(5) putting the quartz tube obtained in the step (4) into a rotary smelting furnace at 800 ℃ to be smelted for 10 hours, rotating all the time in the smelting process to ensure that the raw materials are fully mixed, and cooling to room temperature to obtain a polycrystalline ingot;
(6) and (5) placing the polycrystalline ingot obtained in the step (5) on a vertical zone melting furnace for zone melting growth, wherein the zone melting temperature is 600 ℃, the growth speed is 8mm/h, and after zone melting from beginning to end, cooling to room temperature to obtain the oriented polycrystalline ingot.
(7) And cutting one end of the quartz tube filled with the oriented single crystal ingot, pouring out the oriented single crystal ingot, and cutting off the tip part of the oriented single crystal ingot by using linear cutting to obtain the antimony tellurium selenium base P-type thermoelectric semiconductor crystal bar ingot with the length of about 70mm and uniform and stable performance.
Fig. 9 is a graph showing the thermoelectric figure of merit of the P-type sb-te-se based thermoelectric material prepared in this embodiment as a function of temperature, and when m is 0.010, the thermoelectric figure of merit of the novel P-type sb-te-se based thermoelectric material prepared in this embodiment is improved due to the optimization of carrier concentration, and the zT value around 700K to 800K is about 0.5.
Example 4
(1) Crushing Sb blocks, Sn blocks, Te blocks and Se blocks with commercial purity of 5N;
(2) pouring a dilute nitric acid solution into a quartz tube with one end sealed and the inner diameter of about 12mm, ultrasonically cleaning for 15-20 min, then cleaning twice with clear water and once with absolute ethyl alcohol, and then putting the quartz tube into an oven to dry for 8h at 100 ℃;
(3) adding doping agent Sn block according to the chemical formula Sb2-nSnnTeSe2Weighing 80g of the raw materials in the step (1) according to the stoichiometric ratio of each element, and placing the raw materials into a dried quartz tube, wherein n is 0.08, 0.09, 0.11 and 0.12.
(4) Pumping the vacuum degree of the quartz tube in the step (3) to 10-3Pa, and sealing the other end of the quartz tube by using oxyhydrogen flame;
(5) putting the quartz tube obtained in the step (4) into a rotary smelting furnace at 800 ℃ to be smelted for 10 hours, rotating all the time in the smelting process to ensure that the raw materials are fully mixed, and cooling to room temperature to obtain a polycrystalline ingot;
(6) and (5) placing the polycrystalline ingot obtained in the step (5) on a vertical zone melting furnace for zone melting growth, wherein the zone melting temperature is 600 ℃, the growth speed is 8mm/h, and after zone melting from beginning to end, cooling to room temperature to obtain the oriented polycrystalline ingot.
(7) And cutting one end of the quartz tube filled with the oriented single crystal ingot, pouring out the oriented single crystal ingot, and cutting off the tip part of the oriented single crystal ingot by using linear cutting to obtain the antimony tellurium selenium base P-type thermoelectric semiconductor crystal bar ingot with the length of about 70mm and uniform and stable performance.
Fig. 10 is a graph showing the thermoelectric figure of merit of the P-type sb-te-se based thermoelectric material prepared in this embodiment as a function of temperature, and when n is 0.010, the thermoelectric figure of merit of the novel P-type sb-te-se based thermoelectric material prepared in this embodiment is improved due to the optimization of carrier concentration, and the zT value around 700K to 800K is about 0.5.

Claims (10)

1. A method for constructing an antimony tellurium selenium matrix alloy for thermoelectric materials comprises the following steps:
(1) chemical formula Sb for constructing matrix alloy2Te3-xSexWherein x is more than or equal to 0 and less than or equal to 3, calculating the energy band structure of the matrix alloy through a first principle, selecting the matrix alloy with the highest degeneracy through the energy band structure, and the corresponding chemical formula is Sb2Te3-x′Sex′Wherein x' is more than or equal to 0 and less than or equal to 3; the first principle of principle applies three approximations in the calculation: a non-relativistic approximation; a Born-Oppenheimer approximation, a kernel-fixed approximation; single electron approximation;
(2) preparation of Sb by zone melting2Te3-x″SexThe value of x 'is x' -0.5-x 'and x' +0.7, and the matrix alloy Sb prepared by the test2Te3-x″Sex"the matrix alloy with the highest degree of degeneracy is selected as the matrix alloy for preparing the antimony tellurium selenium-based thermoelectric material.
2. The method of claim 1, wherein in the step (1), the matrix alloy with the highest degeneracy selected by the band structure is Sb2TeSe2(ii) a In step (2), the base alloy Sb2Te3-x″SexThe value of x in the' is more than or equal to 1.5 and less than or equal to 2.7.
3. The method for constructing an antimony tellurium selenium matrix alloy for thermoelectric materials as claimed in claim 2, wherein in the step (2), the matrix alloy with the highest degree of degeneracy is selected as Sb2TeSe2。
4. An Sb-Te-Se-based thermoelectric material, characterized in that the Sb-Te-Se-based thermoelectric material comprises the matrix alloy Sb obtained by the construction method as set forth in claim 32TeSe2And a doping agent M, wherein M is selected from one or a combination of at least two of Ag, Cu, Sn and Pb; the Sb, Te and Se-based thermoelectric material is expressed as Sb2-yMyTeSe2Wherein y is more than or equal to 0.8 and less than or equal to 1.965.
5. The Sb-Te-Se-based thermoelectric material as claimed in claim 4, wherein the dopant is Sn and the Sb-Te-Se-based thermoelectric material is Sb2-nSnnTeSe2Wherein n is more than or equal to 0.08 and less than or equal to 0.12.
6. The Sb-Te-Se-based thermoelectric material as claimed in claim 4, wherein the dopant is Ag and the Sb-Te-Se-based thermoelectric material is Sb2-yAgyTeSe2Wherein y is more than or equal to 0.005 and less than or equal to 0.03.
7. The Sb-Te-Se-based thermoelectric material as claimed in claim 6, wherein the Sb-Te-Se-based thermoelectric materialIs Sb2-yAgyTeSe2Wherein y is more than or equal to 0.02 and less than or equal to 0.03.
8. The Sb-Te-Se-based thermoelectric material as claimed in claim 4, wherein the dopant is Ag and Cu, and the Sb-Te-Se-based thermoelectric material is Sb1.98-zAg0.02CuzTeSe2Wherein z is more than or equal to 0.005 and less than or equal to 0.015.
9. The Sb-Te-Se-based thermoelectric material as claimed in claim 4, wherein the dopant is Ag and Pb, and the Sb-Te-Se-based thermoelectric material is Sb1.98-mAg0.02PbmTeSe2Wherein m is more than or equal to 0.005 and less than or equal to 0.015.
10. The Sb-Te-Se-based thermoelectric material as claimed in claim 4, wherein the thermoelectric figure of merit of the Sb-Te-Se-based thermoelectric material is 0.4-0.5 at a temperature range of 500-800K.
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