Cu2Se-based composite thermoelectric material and preparation and application thereof

Abstract

The invention relates to the technical field of thermoelectric semiconductor materials, in particular to a Cu2Se-based composite thermoelectric material and preparation and application thereof. The Cu2Se-based composite thermoelectric material provided by the invention comprises a main phase Cu1.98 Se and a second phase CoSb3, wherein the chemical general formula of the Cu2Se-based composite thermoelectric material is (1-x) Cu1.98 Se + xCoSb3; wherein x ranges from 0.006 to 0.04. The preparation method comprises the following steps: firstly, uniformly mixing Cu powder and Se powder, and then carrying out ball milling to obtain main phase powder; co powder and Sb powder are evenly mixed and then subjected to ball milling, and second-phase powder is obtained; grinding the main-phase powder and the second-phase powder to obtain mixed-phase powder; and finally, sintering the mixed phase powder to obtain the Cu2Se-based composite thermoelectric material. The Cu2Se-based composite thermoelectric material provided by the invention has the advantages of high stability, good repeatability and excellent performance in a low-temperature region.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric semiconductor materials, and in particular to a Cu2Se-based composite thermoelectric material and its preparation and application. Background Art

[0002] Thermoelectric materials are functional materials that directly convert thermal energy and electrical energy through the movement of charge carriers inside a solid. With the development of science and technology, in the actual production environment, a large amount of energy is inevitably released in the form of waste heat. Thermoelectric materials have shown great development prospects in the technology of converting waste heat into electrical energy. In recent years, Cu2Se-based materials have attracted much attention due to their good electrical properties and ultra-low thermal conductivity. However, due to the easy migration of Cu + ions from the lattice at high temperatures or under large currents, the resulting increase in carrier concentration and decrease in stability limit their practical applications.

[0003] Composite second phases are common strategies for optimizing the thermoelectric performance of Cu2Se, such as introducing nanoscale second phases (such as Cu nanoparticles, Ag2Se) or precipitated phases to reduce lattice thermal conductivity through interface scattering; compounding with graphene or carbon nanotubes to enhance electrical conductivity using highly conductive carbon materials and simultaneously reduce thermal conductivity through interface scattering; however, existing Cu2Se-based composite thermoelectric materials have problems such as poor stability, poor repeatability, and poor performance in the low-temperature region.

[0004] Therefore, it is crucial to provide a technical solution that can solve the above technical problems. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide a Cu2Se-based composite thermoelectric material and its preparation and application. The Cu2Se-based composite thermoelectric material provided by the present invention includes a main phase and a second phase. The main phase is Cu 1.98 Se, and the composite second phase is CoSb3. As the second phase, CoSb3 has a high density of states (DOS) at the valence band top and the degenerate characteristics of light and heavy hole bands. After being compounded with Cu2Se, the band bending at the interface forms an energy barrier, selectively filtering low-energy carriers, thereby enhancing the Seebeck coefficient of the material and avoiding the problem of excessive carrier concentration caused by the superionic state of Cu2Se; while reducing carriers, it enhances interface phonon scattering and reduces lattice thermal conductivity, synergistically optimizing the thermoelectric performance; at the same time, the composite second phase blocks the long-range migration of Cu + ions at high temperatures and under large currents, improving the stability of the material.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] The first object of the present invention is to provide a Cu2Se-based composite thermoelectric material, including a main phase Cu 1.98 Se and a second phase CoSb3, and its chemical general formula is (1-x)Cu 1.98 Se + xCoSb3; wherein, x is 0.006 to 0.04;

[0008] Preferably, x is 0.006, 0.01, 0.02, 0.03, 0.04;

[0009] More preferably, x is 0.02.

[0010] The second object of the present invention is to provide a preparation method of a Cu2Se-based composite thermoelectric material, including the following steps:

[0011] (S1) Mix Cu powder and Se powder and then ball mill to obtain the main phase powder;

[0012] Mix Co powder and Sb powder and then ball mill to obtain the second phase powder;

[0013] (S2) Grind the main phase powder and the second phase powder prepared in step (S1) to obtain a mixed phase powder;

[0014] (S3) Sinter the mixed phase powder obtained in step (S2) to obtain a Cu2Se-based composite thermoelectric material.

[0015] In the present invention, the purities of the Cu powder, Se powder, Co powder and Sb powder used are all 99.99%.

[0016] In an embodiment of the present invention, in step (S1), the molar ratio of Cu powder to Se powder is 1.98:1;

[0017] The molar ratio of Co powder to Sb powder is 1:3.

[0018] In an embodiment of the present invention, in step (S1), during the ball milling process, it is under an argon atmosphere, the rotation speed is 300 to 500 r / min, and the time is 15 to 20 h.

[0019] In an embodiment of the present invention, in step (S2), the molar ratio of the main phase powder to the second phase powder is 0.7 to 0.94:0.06 to 0.3.

[0020] In an embodiment of the present invention, in step (S2), during the grinding process, it is under an argon atmosphere and grind clockwise for 30 to 40 min.

[0021] In an embodiment of the present invention, in step (S3), the sintering treatment is carried out by means of spark plasma sintering.

[0022] In one embodiment of the present invention, in step (S3), during the sintering process, it is in a vacuum state, the pressure is 50 - 60 MPa, the heating rate is 50 - 60 K / min, the temperature is 753 - 803 K, and the time is 3 - 5 min.

[0023] The third object of the present invention is to provide an application of the Cu2Se-based composite thermoelectric material in emerging cross fields, the field of electronics and information technology, or the field of energy and environment.

[0024] In one embodiment of the present invention, the emerging cross fields include thermo-photoelectricity, thermo-catalysis, thermo-electromagnetism, and bio-thermoelectricity;

[0025] The field of electronics and information technology includes 5G / 6G communication, flexible electronic devices, or micro-components;

[0026] The field of energy and environment includes waste heat recovery or solar thermal utilization.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The Cu2Se-based composite thermoelectric material provided by the present invention compositing CoSb3 in Cu 1.98 Se reduces the carrier concentration while appropriately reducing the thermal conductivity through interface scattering. This Cu2Se-based composite thermoelectric material has excellent thermoelectric figure of merit.

[0029] (2) The Cu2Se-based composite thermoelectric material provided by the present invention improves the stability of the Cu2Se-based thermoelectric material, making up for the disadvantage of poor stability of the Cu2Se-based thermoelectric material.

[0030] (3) The preparation method of the Cu2Se-based composite thermoelectric material provided by the present invention is simple in operation, low in raw material cost, and the raw materials are clean. The prepared Cu2Se-based composite thermoelectric material has high stability and good repeatability.

[0031] (4) The Cu2Se-based composite thermoelectric material provided by the present invention improves the thermoelectric performance of the Cu2Se-based thermoelectric material in the low-temperature region, making up for the problem of poor performance in the low-temperature region of this material. Description of the Drawings

[0032] Figure 1 XRD diagrams of Cu 1.98 Se, CoSb3, and the Cu2Se-based composite thermoelectric material ((1 - x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0033] Figure 2For the temperature dependence change diagram of the electrical conductivity (σ) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0034] Figure 3 For the temperature dependence change diagram of the Seebeck coefficient (S) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0035] Figure 4 For the temperature dependence change diagram of the power factor (PF) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0036] Figure 5 For the temperature dependence change diagram of the thermal conductivity (κ) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0037] Figure 6 For the temperature dependence change diagram of the thermoelectric figure of merit (zT) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.006, 0.01, 0.02, 0.03, 0.04 respectively;

[0038] Figure 7 For the time-dependent change diagram of the resistance stability coefficient (R / R0) of the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se + xCoSb3), where x is 0, 0.02 respectively. Detailed implementation manner

[0039] The present invention provides a Cu2Se-based composite thermoelectric material, including a main phase Cu 1.98 Se and a second phase CoSb3, and its chemical general formula is (1-x)Cu 1.98 Se + xCoSb3; where x is 0.006 to 0.04;

[0040] Preferably, x is 0.006, 0.01, 0.02, 0.03, 0.04;

[0041] More preferably, x is 0.02.

[0042] The present invention provides a method for preparing a Cu2Se-based composite thermoelectric material, comprising the following steps:

[0043] (S1) Mix Cu powder and Se powder and then ball-mill them to obtain the main-phase powder;

[0044] Mix Co powder and Sb powder and then ball-mill them to obtain the second-phase powder;

[0045] (S2) Grind the main-phase powder and the second-phase powder prepared in step (S1) to obtain a mixed-phase powder;

[0046] (S3) Sinter the mixed-phase powder obtained in step (S2) to obtain the Cu2Se-based composite thermoelectric material.

[0047] In the present invention, the purities of the Cu powder, Se powder, Co powder and Sb powder used are all 99.99%.

[0048] In an embodiment of the present invention, in step (S1), the molar ratio of Cu powder to Se powder is 1.98:1;

[0049] The molar ratio of Co powder to Sb powder is 1:3.

[0050] In an embodiment of the present invention, in step (S1), during the ball-milling process, it is under an argon atmosphere, the rotation speed is 300 - 500 r / min, and the time is 15 - 20 h.

[0051] In an embodiment of the present invention, in step (S2), the molar ratio of the main-phase powder to the second-phase powder is 0.7 - 0.94:0.06 - 0.3.

[0052] In an embodiment of the present invention, in step (S2), during the grinding process, it is under an argon atmosphere and grind clockwise for 30 - 40 min.

[0053] In an embodiment of the present invention, in step (S3), the sintering treatment is carried out by means of spark plasma sintering.

[0054] In an embodiment of the present invention, in step (S3), during the sintering treatment process, it is under a vacuum state, the pressure is 50 - 60 MPa, the heating rate is 50 - 60 K / min, the temperature is 753 - 803 K, and the time is 3 - 5 min.

[0055] The present invention provides an application of the Cu2Se-based composite thermoelectric material in emerging cross fields, the field of electronics and information technology or the field of energy and environment.

[0056] In one embodiment of the present invention, the new cross - fields include thermoelectric - optoelectronics, thermoelectric catalysis, thermoelectromagnetics, and bio - thermoelectrics;

[0057] The field of electronics and information technology includes 5G / 6G communication, flexible electronic devices or micro - components;

[0058] The field of energy and environment includes waste heat recovery or solar thermal utilization.

[0059] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0060] In the following embodiments, unless otherwise specified, the reagents used are commercially available reagents, and the detection means and methods used are conventional detection means and methods in the art.

[0061] Example 1

[0062] This example provides a preparation method of a Cu2Se - based composite thermoelectric material (0.994Cu 1.98 Se + 0.006CoSb3), which specifically includes the following steps:

[0063] (S1) High - purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) are strictly weighed in a glove box under an argon atmosphere into a ball - milling tank according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g). Then it is placed on a high - energy ball mill, the rotation speed is adjusted to 400 r / min, and ball - milling is carried out for 18 h. After the ball - milling is completed, the ball - milling tank is opened in the glove box under an argon atmosphere to prevent the powder from oxidizing, and the main - phase powder: Cu 1.98 Se (XRD pattern is as Figure 1 shown);

[0064] (S2) High - purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) are strictly weighed in a glove box under an argon atmosphere into a ball - milling tank according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g). Then it is placed on a high - energy ball mill, the rotation speed is adjusted to 400 r / min, and ball - milling is carried out for 18 h. After the ball - milling is completed, the ball - milling tank is opened in the glove box under an argon atmosphere to prevent the powder from oxidizing, and the second - phase powder: CoSb3 (XRD pattern is as Figure 1 shown);

[0065] (S3) Place the matrix phase powder (4.938 g) prepared in step (S1) and the second phase powder (0.062 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain a mixed phase powder;

[0066] (S4) Load the mixed phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then place it in a spark plasma sintering furnace, evacuate, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; wait for the furnace to cool and then take out the mold, and polish the carbon paper on the surface of the sample with sandpaper to obtain a Cu2Se-based composite thermoelectric material (0.994Cu 1.98 Se + 0.006CoSb3, as shown in the XRD pattern Figure 1 .

[0067] Example 2

[0068] This example provides a preparation method for a Cu2Se-based composite thermoelectric material (0.99Cu 1.98 Se + 0.01CoSb3), which specifically includes the following steps:

[0069] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) and place them in a ball milling tank. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling tank in a glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the matrix phase powder: Cu 1.98 Se;

[0070] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) and place them in a ball milling tank. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling tank in a glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second phase powder: CoSb3;

[0071] (S3) Place the primary phase powder prepared in step (S1) (4.898 g, weighed using an electronic balance with a precision of 0.0001 g) and the secondary phase powder prepared in step (S2) (0.102 g, weighed using an electronic balance with a precision of 0.0001 g) in an agate mortar, and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain the mixed phase powder;

[0072] (S4) Place the mixed phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then put it into a spark plasma sintering furnace, evacuate, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; wait for the furnace to cool down and then take out the mold, and polish off the carbon paper on the surface of the sample to obtain the Cu2Se-based composite thermoelectric material (0.99Cu 1.98 Se + 0.01CoSb3, as shown in the XRD pattern Figure 1 .

[0073] Example 3

[0074] This example provides a preparation method for a Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3), which specifically includes the following steps:

[0075] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, weighed using an electronic balance with a precision of 0.0001 g) and place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the primary phase powder: Cu 1.98 Se;

[0076] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, weighed using an electronic balance with a precision of 0.0001 g) and place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the secondary phase powder: CoSb3;

[0077] (S3) Place the matrix phase powder (4.797 g) prepared in step (S1) and the second phase powder (0.203 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain the mixed phase powder;

[0078] (S4) Place the mixed phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then put it into a furnace for spark plasma sintering. Evacuate the air, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; After waiting for the furnace to cool, take out the mold and polish the carbon paper on the surface of the sample with sandpaper to obtain the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3, as shown in the XRD pattern Figure 1 as shown).

[0079] Example 4

[0080] This example provides a preparation method for a Cu2Se-based composite thermoelectric material (0.97Cu 1.98 Se + 0.03CoSb3), which specifically includes the following steps:

[0081] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and the weighing is carried out using an electronic balance with a precision of 0.0001 g) and strictly place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the matrix phase powder: Cu 1.98 Se;

[0082] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and the weighing is carried out using an electronic balance with a precision of 0.0001 g) and strictly place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second phase powder: CoSb3;

[0083] (S3) Place the matrix phase powder (4.699 g) prepared in step (S1) and the second phase powder (0.301 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain the mixed phase powder;

[0084] (S4) Place the mixed phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then put it into a spark plasma sintering furnace, evacuate, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; wait for the furnace to cool and then take out the mold, and polish off the carbon paper on the surface of the sample to obtain the Cu2Se-based composite thermoelectric material (0.97Cu 1.98 Se + 0.03CoSb3, as shown in the XRD pattern Figure 1 ).

[0085] Example 5

[0086] This example provides a preparation method for the Cu2Se-based composite thermoelectric material (0.96Cu 1.98 Se + 0.04CoSb3), which specifically includes the following steps:

[0087] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) and place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the matrix phase powder: Cu 1.98 Se;

[0088] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) and place them in a ball milling jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second phase powder: CoSb3;

[0089] (S3) Place the matrix powder (4.603 g) prepared in step (S1) and the second-phase powder (0.397 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain a mixed-phase powder;

[0090] (S4) Place the mixed-phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then put it into a spark plasma sintering furnace, evacuate, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; wait for the furnace to cool down and then take out the mold, and polish the carbon paper on the surface of the sample with sandpaper to obtain a Cu2Se-based composite thermoelectric material (0.96Cu 1.98 Se + 0.04 CoSb3, as shown in the XRD pattern Figure 1 ).

[0091] Comparative Example 1

[0092] This comparative example provides a preparation method for a Cu2Se-based thermoelectric material (Cu 1.98 Se), which specifically includes the following steps:

[0093] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) and place them in a ball milling tank. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 18 h. After the ball milling is completed, open the ball milling tank in a glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the powder: Cu 1.98 Se;

[0094] (S2) Place the powder prepared in step (S1) into a graphite mold with a diameter of 10 mm in a glove box under an argon atmosphere, then put it into a spark plasma sintering furnace, evacuate, apply a pre-pressure, set the pressure to 55 MPa, the heating rate to 55 K / min, the sintering temperature to 778 K, and sinter for 4 min; wait for the furnace to cool down and then take out the mold, and polish the carbon paper on the surface of the sample with sandpaper to obtain a Cu2Se-based thermoelectric material (Cu 1.98 Se, as shown in the XRD pattern Figure 1 ).

[0095] Performance analysis:

[0096] Figure 1 For Cu 1.98XRD patterns of Se, CoSb3, the Cu2Se-based composite thermoelectric materials prepared in Examples 1-5, and the Cu2Se-based thermoelectric material prepared in Comparative Example 1; by Figure 2 It can be found that all the prepared Cu2Se-based composite thermoelectric materials can well correspond to the diffraction peaks of Cu2Se, and the diffraction peaks of all the Cu2Se-based composite thermoelectric materials do not shift, indicating that CoSb3 does not enter the lattice but exists in the matrix in the form of a second phase. No other impurity phases are found in the composite samples, indicating that CoSb3 does not react with the matrix, and the matrix can still maintain good chemical stability in the presence of CoSb3; when the composite content is small (x < 0.01), due to the small composite content, it is difficult to detect the CoSb3 diffraction peak in the spectrum; when the composite content is large (x > 0.01), with the increase of the content, the CoSb3 diffraction peak gradually becomes significant in the spectrum.

[0097] The Cu2Se-based composite thermoelectric materials prepared in Examples 1-5 and the Cu2Se-based thermoelectric material prepared in Comparative Example 1 were cut into standard rectangular strip samples, and the width (3.5 mm) and thickness (1.5 mm) of the samples were measured, and the electrical conductivity ( Figure 2 ) and Seebeck coefficient test ( Figure 3 ) of the samples were carried out.

[0098] By Figure 2 and Figure 3 It can be found that S increases with the increase of temperature, and S of all composite samples is higher than that of the matrix ( Figure 2 ). σ is opposite to S, decreasing with the increase of temperature, and σ of all composite samples is lower than that of the matrix ( Figure 3 ). At low temperatures, S generally increases with the increase of the composite content, while σ decreases with the increase of the composite amount. This is because the agglomeration of phases in the structure may lead to the formation of large interfaces in the grain boundary region, which is considered to cause strong scattering of carriers; the second phase itself is a p-type material with a low carrier concentration and poor conductivity, resulting in a decrease in the carrier concentration after composite, thus causing an increase in S and a decrease in σ at low temperatures. And CoSb3 has a high density of states (DOS) at the valence band top and the degenerate characteristics of the light and heavy hole bands. After being combined with Cu2Se, the energy band bending at the interface forms an energy barrier, selectively filtering low-energy carriers, thereby improving S, and at the same time optimizing the carrier concentration through interface charge transfer to avoid the problem of excessive carrier concentration caused by the superionic state of Cu2Se.

[0099] The surfaces of the Cu2Se-based composite thermoelectric materials prepared in Examples 1-5 and the Cu2Se-based thermoelectric material prepared in Comparative Example 1 were coated with graphite, and after measuring the sample thickness (1.5 mm), the thermal diffusivity test ( Figures 4 - 6 ) was carried out.

[0100] pass Figure 4 It can be found that Cu2Se based composite thermoelectric materials ((1-x)Cu 1.98 Se+xCoSb3) With the increase of the second phase composite content, the power factor of the matrix is significantly improved in the low and medium temperature regions, and the power factors of all Cu2Se-based composite thermoelectric materials are improved to a certain extent.

[0101] pass Figure 5 It can be found that due to the instability of the matrix, as the temperature rises during the test, Cu + Ions diffuse to the surface, leading to the precipitation of Cu. The precipitated Cu has a larger heat capacity, causing the thermal diffusivity of the matrix to gradually increase at high temperatures. The reduced electrical conductivity after composite formation reduces the contribution of electronic thermal conductivity, resulting in a decrease in the thermal conductivity of all Cu2Se-based composite thermoelectric materials compared to the matrix. Furthermore, the introduction of the second phase, leading to phonon scattering, reduces thermal conductivity to a certain extent.

[0102] pass Figure 6 It can be found that the final zT value obtained by calculation is that the Cu2Se-based composite thermoelectric material ((1-x)Cu 1.98 Se+xCoSb3) obtains a maximum zT of 2.88 at x=0.02 at 973K, and its stability is improved compared with the matrix.

[0103] The Cu2Se-based composite thermoelectric materials prepared in Examples 1 to 5 and the Cu2Se-based thermoelectric material prepared in Comparative Example 1 (rectangular strip samples with a cross section of approximately 3.5 mm × 1.5 mm) were connected to a four-probe fixture at both ends through silver paste and subjected to a constant current density (J = 20-30 A / cm 2 )Continue loading and record the resistance change every half hour ( Figure 7 ).

[0104] pass Figure 7 It can be found that at t = 1800s, the R / R0 curve of the matrix has begun to deviate. As the time of applying current increases, the R / R0 curve of the matrix gradually deviates. 1.98 The R / R0 curve of Cu2Se+0.02CoSb3) shows a high degree of stability in the entire test time interval, and always remains stable near 1. This phenomenon clearly shows that compared with the matrix material, the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se+0.02CoSb3) has better stability under the same current conditions and can effectively resist performance fluctuations caused by long-term application of current.

[0105] In summary, the Cu2Se-based composite thermoelectric material provided by the present invention exhibits excellent comprehensive performance. Compared with the uncomposite matrix, the Cu2Se-based composite thermoelectric material has a more reasonable carrier concentration range, higher electrical properties and lower thermal conductivity; to a certain extent, it improves the thermoelectric performance of the matrix in the low-temperature region. Among them, the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3) has the most excellent thermoelectric figure of merit. At 923K, the zT value is 2.88, and it has higher stability. The Cu2Se-based composite thermoelectric material provided by the present invention can be further applied to emerging cross-cutting fields, the field of electronics and information technology, or the field of energy and environment.

[0106] Example 6

[0107] This example provides a preparation method for the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3), which specifically includes the following steps:

[0108] (S1) High-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) are strictly weighed in a ball milling jar in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10g, and weighing is carried out using an electronic balance with a precision of 0.0001g). Place it on a high-energy ball mill, adjust the rotation speed to 300r / min, and ball mill for 20h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the main phase powder: Cu 1.98 Se;

[0109] (S2) High-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) are strictly weighed in a ball milling jar in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10g, and weighing is carried out using an electronic balance with a precision of 0.0001g). Place it on a high-energy ball mill, adjust the rotation speed to 300r / min, and ball mill for 20h. After the ball milling is completed, open the ball milling jar in the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second phase powder: CoSb3;

[0110] (S3) Place the main phase powder (4.797g) prepared in step (S1) and the second phase powder (0.203g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. In order to ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 30min to obtain the mixed phase powder;

[0111] (S4) Load the mixed-phase powder prepared in step (S3) into a graphite mold with a diameter of 8 mm inside a glove box under an argon atmosphere, then place it in a spark plasma sintering furnace, evacuate the air, apply a pre-pressure, set the pressure to 50 MPa, the heating rate to 50 K / min, the sintering temperature to 753 K, and sinter for 5 min; wait for the furnace to cool down and then take out the mold, and polish the carbon paper on the surface of the sample with sandpaper to obtain the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3).

[0112] Example 7

[0113] This example provides a method for preparing a Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3), which specifically includes the following steps:

[0114] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) into a ball milling jar, place it on a high-energy ball mill, adjust the rotation speed to 500 r / min, ball mill for 15 h, after the ball milling is completed, open the ball milling jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the main-phase powder: Cu 1.98 Se;

[0115] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) into a ball milling jar, place it on a high-energy ball mill, adjust the rotation speed to 500 r / min, ball mill for 15 h, after the ball milling is completed, open the ball milling jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second-phase powder: CoSb3;

[0116] (S3) Place the main-phase powder (4.797 g) prepared in step (S1) and the second-phase powder (0.203 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. In order to ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 40 min to obtain the mixed-phase powder;

[0117] (S4) Load the mixed-phase powder prepared in step (S3) into a graphite mold with a diameter of 12 mm inside a glove box under an argon atmosphere. Then, place it in a spark plasma sintering furnace, evacuate the air, apply a pre-pressure of 60 MPa, set the heating rate at 60 K / min, the sintering temperature at 803 K, and sinter for 3 min. After waiting for the furnace to cool, take out the mold and polish off the carbon paper on the surface of the sample with sandpaper to obtain the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3).

[0118] Example 8

[0119] This example provides a method for preparing a Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3), which specifically includes the following steps:

[0120] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, and the total amount of Cu powder and Se powder is 10 g. The weighing is carried out using an electronic balance with a precision of 0.0001 g) and strictly place them in a ball mill jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 15 h. After the ball milling is completed, open the ball mill jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the main-phase powder: Cu 1.98 Se;

[0121] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, and the total amount of Cu powder and Se powder is 10 g. The weighing is carried out using an electronic balance with a precision of 0.0001 g) and strictly place them in a ball mill jar. Put it on a high-energy ball mill, adjust the rotation speed to 400 r / min, and ball mill for 15 h. After the ball milling is completed, open the ball mill jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second-phase powder: CoSb3;

[0122] (S3) Place the main-phase powder (4.797 g) prepared in step (S1) and the second-phase powder (0.203 g) prepared in step (S2) in an agate mortar and compound the two phases by hand grinding. To ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain the mixed-phase powder;

[0123] (S4) Load the mixed-phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm inside a glove box under an argon atmosphere, then place it in a spark plasma sintering furnace, evacuate the air, apply a pre-pressure, set the pressure to 50 MPa, the heating rate to 60 K / min, the sintering temperature to 753 K, and sinter for 5 min; wait for the furnace to cool down and then take out the mold, and polish the carbon paper on the surface of the sample with sandpaper to obtain the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3).

[0124] Example 9

[0125] This example provides a method for preparing a Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3), which specifically includes the following steps:

[0126] (S1) Weigh high-purity Cu powder (purity 99.99%) and Se powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Cu powder to Se powder is 1.98:1, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) into a ball milling jar, place it on a high-energy ball mill, adjust the rotation speed to 400 r / min, ball mill for 20 h. After the ball milling is completed, open the ball milling jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the main-phase powder: Cu 1.98 Se;

[0127] (S2) Weigh high-purity Co powder (purity 99.99%) and Sb powder (purity 99.99%) strictly in a glove box under an argon atmosphere according to the stoichiometric ratio (the molar ratio of Co powder to Sb powder is 1:3, the total amount of Cu powder and Se powder is 10 g, and weighing is carried out using an electronic balance with a precision of 0.0001 g) into a ball milling jar, place it on a high-energy ball mill, adjust the rotation speed to 400 r / min, ball mill for 20 h. After the ball milling is completed, open the ball milling jar inside the glove box under an argon atmosphere to prevent the powder from oxidizing, and obtain the second-phase powder: CoSb3;

[0128] (S3) Place the main-phase powder (4.797 g) prepared in step (S1) and the second-phase powder (0.203 g) prepared in step (S2) in an agate mortar, and compound the two phases by hand grinding. In order to ensure the same mixing degree for each sample, grind strictly in a clockwise direction for 35 min to obtain the mixed-phase powder;

[0129] (S4) Load the mixed-phase powder prepared in step (S3) into a graphite mold with a diameter of 10 mm inside a glove box under an argon atmosphere, then place it in a spark plasma sintering furnace, evacuate the air, perform pre-pressing, set the pressure to 60 MPa, the heating rate to 50 K / min, the sintering temperature to 803 K, and sinter for 3 min; wait for the furnace to cool down and then take out the mold, and polish off the carbon paper on the surface of the sample with sandpaper to obtain the Cu2Se-based composite thermoelectric material (0.98Cu 1.98 Se + 0.02CoSb3).

[0130] The performance of the Cu2Se-based composite thermoelectric materials prepared in Examples 6 to 9 is basically equivalent to that of the Cu2Se-based composite thermoelectric material prepared in Example 3.

[0131] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative efforts. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the interpretation of the present invention should be within the protection scope of the present invention.

Claims

1. A Cu2Se-based composite thermoelectric material, characterized in that, including a main phase Cu 1.98 Se and a secondary phase CoSb3 Its chemical general formula is (1 - x)Cu 1.98 Se + xCoSb3; where x is from 0.006 to 0.

04.

2. A Cu2Se-based composite thermoelectric material according to claim 1, characterized in that, x is 0.006, 0.01, 0.02, 0.03, 0.

04.

3. A Cu2Se-based composite thermoelectric material according to claim 1, characterized in that, x is 0.

02.

4. A method for preparing a Cu2Se-based composite thermoelectric material according to any one of claims 1 to 3, characterized in that, It includes the following steps: (S1) Mix Cu powder and Se powder evenly and then ball-mill them to obtain the main-phase powder; Mix Co powder and Sb powder evenly and then ball-mill them to obtain the second-phase powder; (S2) Grind the main-phase powder and the second-phase powder prepared in step (S1) to obtain the mixed-phase powder; (S3) Sinter the mixed-phase powder obtained in step (S2) to obtain the Cu2Se-based composite thermoelectric material.

5. The preparation method of a Cu2Se-based composite thermoelectric material according to claim 4, characterized in that, In step (S1), the molar ratio of Cu powder to Se powder is 1.98:1; The molar ratio of Co powder to Sb powder is 1:

3.

6. The preparation method of a Cu2Se-based composite thermoelectric material according to claim 4, characterized in that, In step (S1), during the ball-milling process, it is under an argon atmosphere, the rotation speed is 300 - 500 r / min, and the time is 15 - 20 h.

7. The preparation method of a Cu2Se-based composite thermoelectric material according to claim 4, wherein, In step (S2), the molar ratio of the main-phase powder to the second-phase powder is 0.96 - 0.994:0.006 - 0.

04.

8. The preparation method of a Cu2Se-based composite thermoelectric material according to claim 4, characterized in that, In step (S2), during the grinding process, it is under an argon atmosphere and grind clockwise for 30 - 40 min.

9. The preparation method of a Cu2Se-based composite thermoelectric material according to claim 4, characterized in that, In step (S3), during the sintering process, it is under a vacuum state, the pressure is 50 - 60 MPa, the heating rate is 50 - 60 K / min, the temperature is 753 - 803 K, and the time is 3 - 5 min.

10. Application of a Cu2Se-based composite thermoelectric material as described in any one of claims 1 - 3 in emerging cross fields, electronic and information technology fields, or energy and environmental fields.

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