阅读说明：本技术 一种单质碲基复合热电材料的制备方法 (Preparation method of elemental tellurium-based composite thermoelectric material ) 是由 陈少平 安德成 王文先 樊文浩 吴玉程 孟庆森 于 2019-09-27 设计创作，主要内容包括：一种单质碲基复合热电材料的制备方法,属于热电材料领域,其特征在于该热电材料化学式为Te<Sub>1-x</Sub>(Sb<Sub>2</Sub>Se<Sub>3</Sub>)<Sub>x</Sub>,0≤x≤0.2。本发明所述制备方法包括如下步骤：按上述化学式摩尔分数配比称量各原料组分,将Te块、Sb粉和Se粉真空封装于镀碳石英管中；再将石英管置于垂直管式炉中熔炼；随后进行退火处理；最后将得到的铸锭研磨成细粉,再进行放电等离子烧结成致密的块体具有很低的热导率和较高的热电性能,其热电优值达到0.95。本发明通过熔炼工艺、退火工艺、放电等离子烧结工艺来提高单质碲基复合热电材料的热电性能。与现有技术相比,通过引入硒化锑组元,实现载流子浓度和晶格热导率的协同优化,工艺过程简单可控,成本低。(A preparation method of a simple substance tellurium-based composite thermoelectric material belongs to the field of thermoelectric materials and is characterized in that the thermoelectric material has a chemical formula of Te 1‑x (Sb 2 Se 3 ) x X is more than or equal to 0 and less than or equal to 0.2. The preparation method comprises the following steps: weighing the raw material components according to the molar fraction ratio of the chemical formula, and vacuum packaging the Te block, Sb powder and Se powder in a carbon-plated quartz tube; then putting the quartz tube into a vertical tube furnace for smelting; then carrying out annealing treatment; finally grinding the obtained cast ingot into fine powder, and sintering the fine powder into compact blocks with low density by discharge plasmaThe thermal conductivity and the high thermoelectric performance, and the thermoelectric figure of merit reaches 0.95. The thermoelectric property of the elemental tellurium-based composite thermoelectric material is improved through a smelting process, an annealing process and a discharge plasma sintering process. Compared with the prior art, the synergistic optimization of the carrier concentration and the lattice thermal conductivity is realized by introducing the antimony selenide component, the process is simple and controllable, and the cost is low.)

1. The preparation method of the elemental tellurium-based composite thermoelectric material is characterized in that Sb is regulated and controlled₂Se₃The method comprises the following steps of (1) optimizing a hole carrier concentration range according to the component content, constructing a multi-dimensional defect structure containing zero-dimensional displacement site defects, one-dimensional dislocation, two-dimensional crystal boundaries and a three-dimensional second phase in a Te matrix, reducing the lattice thermal conductivity of the material in the whole working temperature range, and cooperatively optimizing the electric-thermal transport performance of the material, so that the preparation method of the elemental tellurium-based composite thermoelectric material with improved thermoelectric performance based on the Te elemental polycrystal is realized, and comprises the following steps:

(1) adding Te block, Sb powder and Se powder with the purity of not less than 99.99 percent according to Te_1-x(Sb₂Se₃)_xWeighing the raw material components according to the molar fraction ratio, filling the raw material components into a carbon-plated quartz tube, and vacuumizing and packaging the carbon-plated quartz tube;

(2) placing the quartz tube filled with the simple substance raw materials in the step (1) in a vertical tube furnace for heating, slowly heating to a melting temperature to enable the raw materials to fully react in a molten state, and then quenching in water to obtain an initial ingot;

(3) vacuum packaging the initial ingot obtained in the step (2) in a carbon-plated quartz tube again, putting the carbon-plated quartz tube into a vertical tube furnace, heating for annealing, and then quenching to obtain an annealed ingot;

(4) and (4) grinding the annealed ingot obtained in the step (3) into fine powder, filling the fine powder into a graphite mold, performing discharge plasma sintering, and then performing furnace cooling to obtain the compact blocky Te-based composite thermoelectric material.

2. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 1, wherein the process conditions of heating and melting in the step (2) are as follows: heating the quartz tube from room temperature to 600-700 ℃ at a heating rate of 50-80 ℃ per hour, and keeping the temperature for 2-4 days to enable the raw materials to fully react in a molten state.

3. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 2, wherein the heating and melting process in the step (2) is carried out under the conditions that the quartz tube is heated from room temperature to 650 ℃ at a heating rate of 60 ℃ per hour and is kept warm for 3 days.

4. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 1, wherein the process conditions of the temperature-raising annealing in the step (3) are as follows: heating the quartz tube from room temperature to 400-500 ℃ at a rate of 100-200 ℃ per hour, and keeping the temperature for 2-4 days.

5. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 4, wherein the temperature-raising annealing in the step (3) is carried out by raising the temperature of the quartz tube from room temperature to 450 ℃ at a rate of 150 ℃ per hour and maintaining the temperature for 3 days.

6. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 1, wherein the process conditions of spark plasma sintering in the step (4) are as follows: vacuumizing the discharge plasma sintering furnace to below 30Pa, heating to 390-410 ℃ at a heating rate of 70 ℃/min, adjusting the sintering pressure to 40-50 MPa, and keeping constant temperature and constant pressure for 5-10 min to perform discharge plasma sintering.

7. The method for preparing the elemental tellurium-based composite thermoelectric material as claimed in claim 6, wherein the discharge plasma sintering process conditions in the step (4) are that the temperature is raised to 400 ℃ at a heating rate of 70 ℃/min, the sintering pressure is 45MPa, and the heat preservation time is 8 min.

Technical Field

The invention relates to a preparation method of an elemental tellurium-based composite thermoelectric material, belongs to the field of thermoelectric materials, and particularly relates to an elemental tellurium-based composite thermoelectric material which optimizes a hole carrier concentration interval by regulating and controlling the content of Sb2Se3 component and simultaneously constructs a multidimensional defect structure comprising zero-dimensional displacement site defects, one-dimensional dislocation, two-dimensional crystal boundaries and a three-dimensional second phase in a Te matrix and a preparation method thereof.

Background

The thermoelectric energy conversion material is a new energy material which has no pollutant emission, no transmission part, no noise and high reliability, can directly convert heat energy into electric energy by utilizing the directional motion of carriers in a solid based on the Seebeck effect, and is a new-generation green energy technology with great application prospect.

The energy conversion efficiency of thermoelectric materials is generally characterized by a dimensionless thermoelectric figure of merit ZT, ZT = S²σ T/κ, wherein: t is absolute temperature, S is Seebeck coefficient, σ is electrical conductivity, and κ is total thermal conductivity. Total thermal conductivity κ is determined by electronic thermal conductivity κ_eAnd lattice thermal conductivity κ_LTwo parts are formed. The Seebeck coefficient S, the electric conductivity sigma and the electronic thermal conductivity kappa of three physical parameters for determining the thermoelectric figure of merit ZT_eThe strong mutual coupling effect exists between the two materials, so that the thermoelectric performance of the material cannot be effectively improved through single parameter regulation. And the lattice thermal conductivity is a parameter which can be relatively independently regulated and controlled and influences the thermoelectric property of the material. Therefore, the power factor (S) is enhanced by synergistically regulating the relationship between electrical transport and heat transport, i.e., chemical doping²Sigma) and simultaneously constructing a multi-scale defect structure to enhance phonon scattering so as to reduce the lattice thermal conductivity kappa of the material_LAnd further achieving a net increase in ZT values has been a research goal in the field of thermoelectric materials.

Te is an important simple substance thermoelectric energy material, and the high ZT value is obtained at present, and the electric transmission performance of the material is improved mainly through the optimization of the concentration of a current carrier. The Kao-Villa and Kao-Richter subjects in 2017 are sequentially doped with As, Sb and Bi single elements to increase the carrier concentration to 10¹⁹cm^-3. However, the related research on the heat transfer property of Te is relatively few at present, the reduction of the lattice thermal conductivity of Te still faces the challenge, and the preparation of high-performance Te-based thermoelectric material with low thermal conductivity by a proper method has important significance.

Disclosure of Invention

The invention relates to a method for preparing a simple substance tellurium-based composite thermoelectric material, which aims to: overcomes the defects in the prior art, provides a novel elemental Te-based thermoelectric material with low lattice thermal conductivity and a technical scheme of a preparation method thereof, and regulates and controls Sb₂Se₃The method comprises the steps of component content, optimization of a hole carrier concentration range, construction of a multi-dimensional defect structure containing zero-dimensional displacement site defects, one-dimensional dislocation, two-dimensional grain boundaries and a three-dimensional second phase in a Te matrix, reduction of lattice thermal conductivity of materials in the whole working temperature range, cooperative optimization of the electro-thermal transport performance of the materials, and improvement of the thermoelectric performance of the materials based on the Te single substance polycrystal.

The object of the invention can be achieved by the following technical solutions:

the invention relates to a simple substance tellurium-based composite thermoelectric material, which is characterized in that Sb is regulated and controlled₂Se₃The method comprises the following steps of (1) optimizing a hole carrier concentration range according to the component content, constructing a multi-dimensional defect structure containing zero-dimensional displacement site defects, one-dimensional dislocation, two-dimensional crystal boundary and a three-dimensional second phase in a Te matrix, reducing the lattice thermal conductivity of the material in the whole working temperature range, and synergistically optimizing the electric-thermal transport performance of the material, thereby realizing the simple substance tellurium-based composite thermoelectric material with improved thermoelectric performance based on Te simple substance polycrystal, wherein the chemical general formula of the material is Te_1-x(Sb₂Se₃)_xWherein x is more than or equal to 0 and less than or equal to 0.2.

Preferably, x is 0.02 to 0.15, and the hole carrier concentration is relatively preferable in this range.

Further preferably, x is 0.03-0.1, at this time, the hole carrier concentration is optimized, the carrier mobility is high, the electron transport performance is effectively improved, and meanwhile, the lower lattice thermal conductivity can be obtained.

More preferably, when x is 0.05, the thermoelectric figure of merit may reach a peak value of 0.95 at 600K.

The preparation method of the elemental tellurium-based composite thermoelectric material is characterized in that Sb is regulated and controlled₂Se₃The method comprises the following steps of (1) optimizing a hole carrier concentration range according to the component content, constructing a multi-dimensional defect structure containing zero-dimensional displacement site defects, one-dimensional dislocation, two-dimensional crystal boundaries and a three-dimensional second phase in a Te matrix, reducing the lattice thermal conductivity of the material in the whole working temperature range, and cooperatively optimizing the electric-thermal transport performance of the material, so that the preparation method of the elemental tellurium-based composite thermoelectric material with improved thermoelectric performance based on the Te elemental polycrystal is realized, and the method comprises the following steps:

(1) adding Te block, Sb powder and Se powder with the purity of not less than 99.99 percent according to Te_1-x(Sb₂Se₃)_xWeighing the raw material components according to the molar fraction ratio, filling the raw material components into a carbon-plated quartz tube, and vacuumizing and packaging the carbon-plated quartz tube;

(2) placing the quartz tube filled with the simple substance raw materials in the step (1) in a vertical tube furnace for heating, slowly heating to a melting temperature to enable the raw materials to fully react in a molten state, and then quenching in water to obtain an initial ingot;

(3) vacuum packaging the initial ingot obtained in the step (2) in a carbon-plated quartz tube again, putting the carbon-plated quartz tube into a vertical tube furnace, heating for annealing, and then quenching to obtain an annealed ingot;

(4) and (4) grinding the annealed ingot obtained in the step (3) into fine powder, filling the fine powder into a graphite mold, performing discharge plasma sintering, and then performing furnace cooling to obtain the compact blocky Te-based composite thermoelectric material.

Preferably, in the step (1), the preparation method of the carbon-coated quartz tube comprises: and (3) slowly burning the tube body of the quartz tube soaked by the high-purity acetone by using oxyhydrogen flame for later use.

Preferably, in the step (1), the elemental raw materials are sequentially loaded from small to large according to the density when being loaded into the carbon-coated quartz tube.

Preferably, in the step (1), the absolute vacuum degree after vacuum pumping is less than 10^-3Pa。

Preferably, in the step (2), the heating process specifically comprises: heating the quartz tube from room temperature to 600-700 ℃ at a heating rate of 50-80 ℃ per hour, and keeping the temperature for 2-4 days to enable the raw materials to fully react in a molten state.

Further preferably, in the step (2), the heating and melting process specifically includes: the quartz tube was heated from room temperature to 650 ℃ at a ramp rate of 60 ℃ per hour and incubated for 3 days.

Preferably, in the step (3), the temperature-raising annealing process specifically includes: heating the quartz tube from room temperature to 400-500 ℃ at a rate of 100-200 ℃ per hour, and keeping the temperature for 2-4 days.

Further preferably, in the step (3), the temperature-raising annealing process specifically includes: the annealing treatment was performed by heating the quartz tube from room temperature to 450 c at a rate of 150 c per hour and holding for 3 days.

Preferably, in the step (4), the spark plasma sintering process specifically includes: vacuumizing the discharge plasma sintering furnace to below 30Pa, heating to 390-410 ℃ at a heating rate of 70 ℃/min, adjusting the sintering pressure to 40-50 MPa, and keeping constant temperature and constant pressure for 5-10 min to perform discharge plasma sintering.

Further preferably, in the step (4), the process conditions of spark plasma sintering are as follows: the sintering temperature is 400 ℃, the sintering pressure is 45MPa, and the heat preservation time is 8 min.

Compared with the prior art, the preparation method of the elemental tellurium-based composite thermoelectric material has the following remarkable advantages:

the invention mainly researches a Te elementary substance thermoelectric material which has a special energy band structure and a relatively complex quasi-one-dimensional crystal structure, but because the intrinsic lattice thermal conductivity is relatively high, the heat transfer performance still has a large optimization space, which is the main limitation of the thermoelectric performance of the materialFor the reason. The invention optimizes the hole carrier concentration to 2 x 10 by introducing antimony selenide components and chemically doping Te simple substance by using antimony atoms¹⁹cm^-3Left and right; at the same time, the substitution of site defects, lattice distortion dislocation, grain boundary and Sb by selenium atoms is constructed in the Te matrix₂TeSe₂The multidimensional defect microstructure composed of the second phase scatters broadband phonons, so that the lattice thermal conductivity of the multidimensional defect microstructure is greatly reduced to 0.55W/mK, and finally the thermoelectric figure of merit reaches 0.95 at 600K, and the multidimensional defect microstructure becomes a simple substance thermoelectric material with high application value. The method can be specifically summarized as follows:

(1) the adjustment and optimization of the raw material heating melting, high-temperature annealing and discharge plasma sintering process are carried out to obtain the compact elemental Te block thermoelectric material with lower thermal conductivity in the whole working temperature range (300-600K).

(2) By regulating and controlling the content of antimony selenide components, the cooperative optimization of the carrier concentration and the lattice thermal conductivity is realized, so that the hole carrier concentration of the Te matrix reaches an optimized level (to 2 multiplied by 10)¹⁹cm^-3) The electrical transmission performance is significantly improved. Meanwhile, antimony selenide is introduced, a multi-dimensional and multi-size defect structure is formed in a Te matrix, broadband phonon scattering is realized, the lattice thermal conductivity of the material is reduced by about 50%, and under the synergistic effect of increasing the carrier concentration and reducing the lattice thermal conductivity, the thermoelectric figure of merit of the material reaches 0.95 at 600K, and is equivalent to the thermoelectric performance realized by doping Te with toxic arsenic elements. Therefore, the invention has the advantages of environmental protection without pollution and is a high-performance elementary substance thermoelectric material with high application value.

(3) Te provided by the invention_1-x(Sb₂Se₃)_xThe thermoelectric material has high power factor, low heat conductivity, simple preparation process, no volatilization and no segregation in the preparation process, ensures stable performance of the Te elementary substance thermoelectric material, and is suitable for large-scale industrial production.

Drawings

FIG. 1 is a crystal structure diagram of elemental Te;

FIG. 2 shows Te of different compositions_1-x(Sb₂Se₃)_xAn XRD pattern of the thermoelectric material;

FIG. 3 is Te_0.95(Sb₂Se₃)_0.05A fracture SEM and EDS diagram of the thermoelectric material;

FIG. 4 shows Te of different compositions_1-x(Sb₂Se₃)_xA graph of electrical properties of the thermoelectric material versus temperature;

FIG. 5 shows Te of different compositions_1-x(Sb₂Se₃)_xA graph of thermal performance versus temperature for the thermoelectric material;

FIG. 6 shows Te of different compositions_1-x(Sb₂Se₃)_xThermoelectric figure of merit of the thermoelectric material is plotted against temperature.

Detailed Description

The present invention will be described in detail with reference to the accompanying drawings and specific embodiments. The present embodiment is implemented on the premise of the technical solution of the present invention, but the scope of the present invention should include the entire contents of the claims, and is not limited to the following embodiments.

The invention successfully prepares a novel high-performance elemental tellurium-based composite thermoelectric material, and the chemical general formula of the thermoelectric material is Te_1-x(Sb₂Se₃)_xWherein x is more than or equal to 0 and less than or equal to 0.2.

In a preferred embodiment of the present invention, x is 0.02 to 0.15, and the hole carrier concentration is relatively preferable in this range.

In a further preferred embodiment, x is 0.03 to 0.1, and in this case, the hole carrier concentration is optimized, the carrier mobility is high, the electron transport performance is effectively improved, and at the same time, a low lattice thermal conductivity can be obtained.

In a further preferred embodiment, the thermoelectric figure of merit may peak at 0.95 at 600K when x is 0.05.

The preparation method of the elemental tellurium-based composite thermoelectric material comprises the following steps:

(1) adding Te block, Sb powder and Se powder with the purity of not less than 99.99 percent according to Te_1-x(Sb₂Se₃)_xThe raw material components are weighed according to the molar fraction ratio,putting into a carbon-plated quartz tube, and vacuumizing and packaging;

(2) placing the quartz tube filled with the simple substance raw materials in the step (1) in a vertical tube furnace for heating, slowly heating to a melting temperature to enable the raw materials to fully react in a molten state, and then quenching in water to obtain an initial ingot;

(3) vacuum packaging the initial ingot obtained in the step (2) in a carbon-plated quartz tube again, putting the carbon-plated quartz tube into a vertical tube furnace, heating for annealing, and then quenching to obtain an annealed ingot;

(4) and (4) grinding the annealed ingot obtained in the step (3) into fine powder, filling the fine powder into a graphite mold, performing discharge plasma sintering, and then performing furnace cooling to obtain the compact blocky Te-based composite thermoelectric material.

In a preferred embodiment of the present invention, the method for preparing the carbon-coated quartz tube in step (1) specifically comprises: cleaning a quartz tube with deionized water for three times, then cleaning the quartz tube with 95% purity alcohol for three times, placing the quartz tube in an oven, heating the quartz tube to 120 ℃ for 60 minutes; burning and cleaning the quartz tube by using oxyhydrogen flame; pouring high-purity acetone into a quartz tube to soak the tube body, and slowly carbonizing the tube bottom and the tube wall of the quartz tube by oxyhydrogen flame after drying residual acetone liquid; and washing the carbon-plated quartz tube with deionized water for three times, then washing with acetone for three times, and drying to obtain the carbon-plated quartz tube for later use.

In a preferred embodiment of the present invention, the raw material in step (1) is charged into the carbon-coated quartz tube in the order of density from small to large.

In a preferred embodiment of the present invention, the absolute vacuum degree after vacuum pumping in the step (1) is less than 10^-3Pa。

In a preferred embodiment of the present invention, the heating and melting process in step (2) is specifically: heating the quartz tube from room temperature to 600-700 ℃ at a heating rate of 50-80 ℃ per hour, and keeping the temperature for 2-4 days to enable the raw materials to fully react in a molten state. Further preferably, the heating and melting process in the step (2) specifically comprises the following steps: the quartz tube was heated from room temperature to 650 ℃ at a ramp rate of 60 ℃ per hour and incubated for 3 days.

In a preferred embodiment of the present invention, the temperature-raising annealing process in step (3) is specifically: heating the quartz tube from room temperature to 400-500 ℃ at a rate of 100-200 ℃ per hour, and keeping the temperature for 2-4 days. Further preferably, the temperature-raising annealing process in the step (3) specifically comprises: the annealing treatment was performed by heating the quartz tube from room temperature to 450 c at a rate of 150 c per hour and holding for 3 days.

In a preferred embodiment of the present invention, the spark plasma sintering process in step (4) is specifically: vacuumizing the discharge plasma sintering furnace to below 30Pa, heating to 390-410 ℃ at a heating rate of 70 ℃/min, adjusting the sintering pressure to 40-50 MPa, and keeping constant temperature and constant pressure for 5-10 min to perform discharge plasma sintering. Further preferably, in the spark plasma sintering process in the step (4), the sintering temperature is 400 ℃, the sintering pressure is 45MPa, and the heat preservation time is 8 min.