GCM / bismuth telluride-based composite thermoelectric material and preparation method and application thereof

Abstract

The invention relates to a GCM / bismuth telluride-based composite thermoelectric material and a preparation method and application thereof, the structural formula of the composite thermoelectric material is shown as Gd (Co < 0.433 > Mn < 0.567 >) < 2 > / Bi < 0.3 > Sb < 1.7 > Te3, and the composite thermoelectric material is obtained by introducing a magnetic second phase GCM (Gd (Co < 0.433 > Mn < 0.567 >) < 2 >) into a bismuth telluride matrix Bi < 0.3 > Sb < 1.7 > Te3. Compared with the prior art, due to the introduction of the magnetic second phase GCM, a generated built-in magnetic field and magnetic scattering, the mobility is reduced, the Seebeck coefficient is increased, due to the diffusion of the GCM, the carrier concentration is increased, the prepared composite thermoelectric material has high electrical performance, meanwhile, due to the introduction of the GCM, phonon scattering is increased, and the performance of the composite thermoelectric material is improved. According to the GCM / bismuth telluride-based composite thermoelectric material, the crystal lattice thermal conductivity of the composite material is effectively reduced, the GCM / bismuth telluride-based composite thermoelectric material has high conductivity, low thermal conductivity and high thermoelectric performance, and the average zT value of the composite material is increased by 39% within the temperature range of 300-500 K. Wide application prospects are realized.

Description

Technical Field

[0001] The present invention relates to the field of preparation of thermoelectric materials, and in particular to a GCM / bismuth telluride-based composite thermoelectric material, a preparation method thereof, and an application thereof. Background Art

[0002] The continuous increase in the global consumption of fossil energy and environmental deterioration have led to a substantial increase in the demand for sustainable clean energy and its conversion technologies. Thermoelectric materials can directly convert thermal energy into electrical energy, and thus have great potential in solving environmental problems and energy crises. The performance of thermoelectric materials is evaluated by the dimensionless figure of merit thermoelectric figure of merit ZT = α 2 σT / κ, where α, σ, T, and κ are the Seebeck coefficient, electrical conductivity, absolute temperature, and total thermal conductivity, respectively. Excellent thermoelectric materials must have large α, high σ, and low κ at the same time. However, these parameters are strongly correlated, so improving thermoelectric performance to meet actual needs is a process of trade-off. Since the 1950s, Bi2Te3-based compounds (bismuth telluride-based compounds) have been the best thermoelectric materials at room temperature and have been commercially applied. However, its actual potential is still limited and still faces a major challenge.

[0003] Most industrial materials release waste heat between 373 and 473 K, but the highest performance of thermoelectric materials occurs slightly below this range. This is attributed to the premature onset of intrinsic excitation, which has an adverse effect on the Seebeck coefficient and causes heat transport through electron-hole recombination. Therefore, the zT of Bi2Te3-based thermoelectric materials drops sharply above 400 K.

[0004] For example, Chinese Patent CN116281881A discloses a bismuth telluride-based thermoelectric material with the chemical formula Ag 0.01 Bi2Te 2.7 Se 0.3-x MoSe2. Among them, MoSe2 forms a phonon scattering center as a nano second phase, improves the carrier mobility, reduces the lattice thermal conductivity, and the two cooperate to improve the thermoelectric performance of the bismuth telluride-based thermoelectric material. The highest zT can reach 1.28 (375 K), but it still drops sharply after 400 K, and zT is close to 0.9 at 473 K, and its thermoelectric performance still needs to be improved.

[0005] Therefore, it is very important to find a simple and effective method to realize the synergistic optimization of electrothermal transport performance and prepare high-performance Bi2Te3-based thermoelectric materials. Summary of the Invention

[0006] The object of the present invention is to provide a GCM / bismuth telluride-based composite thermoelectric material, its preparation method and application. The prepared composite thermoelectric material effectively solves the problem of poor electrothermal transport performance and has high electrical performance and thermoelectric performance.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] On the one hand, the present invention provides a GCM / bismuth telluride-based composite thermoelectric material, including a bismuth telluride matrix, in which a magnetic second phase GCM is compounded. The chemical formula of the bismuth telluride matrix is Bi 0.3 Sb 1.7 Te3, and the chemical formula of the GCM is Gd(Co 0.433 Mn 0.567 )2. The structural formula of the composite thermoelectric material is expressed as Gd(Co 0.433 Mn 0.567 )2 / Bi 0.3 Sb 1.7 Te3.

[0009] Preferably, the content of GCM in the bismuth telluride matrix is 0.3-1.0 wt%.

[0010] More preferably, the content of GCM in the bismuth telluride matrix is 0.4 wt%.

[0011] On the second hand, the present invention also provides a preparation method of the above-mentioned GCM / bismuth telluride-based composite thermoelectric material, including the following steps:

[0012] S1: Mix three single-element raw materials of Bi, Sb and Te according to the molar ratio of each element in the chemical formula of Bi 0.3 Sb 1.7 Te3, melt and prepare a Bi 0.3 Sb 1.7 Te3 ingot, and obtain Bi 0.3 Sb 1.7 Te3 powder after crushing and grinding;

[0013] S2: Mix three single-element raw materials of Gd, Co and Mn according to the molar ratio of each element in the chemical formula of Gd(Co 0.433 Mn 0.567 )2, and obtain a Gd(Co 0.433 Mn 0.567 )2 ingot by arc melting. Then, through annealing, quenching, crushing and grinding, obtain Gd(Co 0.433 Mn 0.567 )2 powder;

[0014] S3: Mix Gd(Co 0.433 Mn 0.567) 2 powders and Bi 0.3 Sb 1.7 Te3 powders are mixed in proportion and ground under the protection of an inert gas to prepare a uniformly mixed composite powder;

[0015] S4: The composite powder is subjected to vacuum hot pressing and sintering to obtain the GCM / bismuth telluride-based composite thermoelectric material.

[0016] Preferably, in step S1, the purity of the three elemental raw materials of Bi, Sb, and Te is greater than 99.5%. The melting process conditions are as follows: melting temperature 873 - 1273K, heating rate 30 - 50K / min, holding time 8 - 12h. The particle size of the Bi 0.3 Sb 1.7 Te3 powder obtained after crushing and grinding is 100 - 200μm.

[0017] Further preferably, in step S1, the molar ratio between the three elemental raw materials of Bi, Sb, and Te is 0.3:1.7:3, which helps to obtain a high-performance matrix.

[0018] Further preferably, in step S1, the melting temperature is 1073K, the heating rate is 40K / min, and the holding time is 10h.

[0019] Further preferably, in step S1, the melting is carried out in a muffle furnace.

[0020] Further preferably, in step S1, after melting, it is cooled with the furnace.

[0021] Preferably, in step S2, the purity of the three elemental raw materials of Gd, Co, and Mn is greater than 99.5%; the arc melting means melting in an argon atmosphere at 1500 - 1800°C for 3 - 5 minutes, then flipping and remelting, repeating this process 3 - 5 times to obtain a Gd(Co 0.433 Mn 0.567 )2 ingot.

[0022] Further preferably, in step S2, the temperature of the arc melting needs to be higher than the highest melting point among the three metals of Gd, Co, and Mn.

[0023] Further preferably, in step S2, the molar ratio between the three elemental raw materials of Gd, Co, and Mn is 1:0.866:1.134, which helps to obtain a pure second phase.

[0024] Further preferably, in step S2, the Mn elemental raw material needs to be in excess to make up for the weight loss caused by its evaporation during the melting process.

[0025] Further preferably, in step S2, the mass of the Mn elemental raw material is additionally added by 5-15% on the basis of the calculated dosage as a supplement.

[0026] Preferably, in step S2, the annealing refers to annealing the Gd(Co 0.433 Mn 0.567 )2 ingot at 773-1173K for 12-16 days.

[0027] Further preferably, in step S2, the annealing refers to annealing the Gd(Co 0.433 Mn 0.567 )2 ingot at 973K for 14 days.

[0028] Preferably, in step S2, the quenching refers to water quenching.

[0029] Preferably, in step S2, the particle size of the Gd(Co 0.433 Mn 0.567 )2 powder obtained after crushing and grinding is 50-100μm.

[0030] Further preferably, in step S2, the surface oxide layer needs to be removed before crushing and grinding.

[0031] Preferably, in step S3, the inert gas refers to high-purity argon, the purity of the high-purity argon is 99.999%, and the particle size of the composite powder obtained after grinding is 100-200μm.

[0032] Further preferably, in step S3, the grinding time is 20-40min.

[0033] Preferably, in step S4, the vacuum hot pressing sintering is carried out in a vacuum hot pressing device, and the process conditions of the vacuum hot pressing sintering are: the sintering temperature is 623-673K, the axial pressure is 45-60MPa, the heating rate is 30-50K / min, and the heat preservation is 10-14min.

[0034] Further preferably, in step S4, the vacuum hot pressing sintering is a sintering method integrating high temperature and pressure. Under the action of pressure, grain boundary slip makes the powder particles rearrange and fill the relatively large voids in the sample. As the temperature rises, in the high-temperature and high-pressure environment, the particles break, atomic diffusion occurs, and the sample becomes dense and forms.

[0035] Further preferably, in step S4, the vacuum hot pressing device mainly consists of a furnace body, a hydraulic system, a vacuum system, a temperature system, etc. A graphite mold can be placed in the furnace body, pressurization is carried out through a hydraulic press head (hydraulic system), and heating is carried out through a resistance wire (temperature system) to realize the sintering of the sample. The whole process is carried out in a vacuum environment. The specific equipment is as Figure 1as shown

[0036] Further preferably, in step S4, before the vacuum hot-pressing sintering, the composite powder obtained in step S3 needs to be loaded into a graphite mold with a diameter of 8-12 mm for tablet pressing, and the powder is sintered by a vacuum hot-pressing device (HP).

[0037] In the present invention, Gd(Co 0.433 Mn 0.567 )2 powder and Bi 0.3 Sb 1.7 Te3 powder are mixed according to a mass ratio and tablet-pressed by using a graphite mold, which can make the contact of each material powder closer and more sufficient, thus contributing to more sufficient combination of the composite powder during vacuum sintering.

[0038] Further preferably, the method for preparing the GCM / bismuth telluride-based composite thermoelectric material includes the following steps:

[0039] S1: After mixing Bi grains, Sb blocks and Te grains, a BST (Bi 0.3 Sb 1.7 Te3) ingot is prepared by a melting method, and after being broken and ground, BST powder is obtained.

[0040] In this step, commercially available Bi grains, Sb blocks and Te grains with a purity greater than 99.5% are weighed as raw materials according to a molar ratio of Bi grains, Sb blocks and Te grains of 0.3:1.7:3. After mixing the above materials evenly, they are kept in a muffle furnace at 1073 K for 10 h, and after cooling with the furnace, a BST ingot is obtained, and after being broken and ground, the matrix powder of BST is obtained.

[0041] S2: Gd(Co 0.433 Mn 0.567 )2 magnetic second phase is prepared by arc melting Gd blocks, Co blocks and Mn sheets to obtain a GCM ingot. After annealing for 14 days, it is quenched and broken and ground to obtain GCM powder.

[0042] In this step, a ternary GdCoMn magnetic alloy (Gd(Co 0.433 Mn 0.567 )2 magnetic second phase) with a nominal composition of Gd(Co 0.433 Mn 0.567 )2 is prepared by arc melting. A small amount of excess Mn is added before melting to make up for the weight loss caused by its evaporation during the melting process. It is flipped and melted four times in an argon atmosphere to ensure uniformity. Subsequently, the obtained ingot is annealed in a vacuum quartz tube at 973 K for two weeks, and then quenched in water. After removing the surface oxide layer, the annealed ingot is crushed to obtain GCM magnetic second phase powder.

[0043] S3: Mix the Gd(Co 0.433 Mn 0.567 )2 powder with Bi 0.3 Sb 1.7 Te3 powder in a mass ratio, and then grind it for 30 min under the protection of an inert gas to obtain a uniformly mixed composite powder;

[0044] In this step, weigh the BST powder and the GCM magnetic second-phase powder with different mass fractions (0.4 wt%, 0.6 wt%, 0.8 wt%, 1.0 wt%) in a high-purity argon atmosphere, put the mixed powder into an agate mortar and grind it for 30 min to ensure that the BST powder and the GCM powder are fully and uniformly mixed.

[0045] S4: Vacuum hot-press sinter the composite powder to obtain a GCM / bismuth telluride-based composite thermoelectric material.

[0046] Subsequently, load the mixed powder into a graphite mold with a diameter of 10 mm, and sinter the powder through a self-built vacuum hot-press equipment (HP). The sintering temperature is 623 - 673 K, the pressure is 45 - 60 MPa, and the heat preservation time is 10 - 14 min. Finally, cut the sintered cylindrical sample into appropriate shapes and sizes according to the requirements of thermoelectric performance testing.

[0047] Thirdly, the present invention also provides an application of the described GCM / bismuth telluride-based composite thermoelectric material in a thermoelectric refrigeration device.

[0048] The present invention provides a GCM / bismuth telluride-based composite thermoelectric material, which has high electrical properties, low thermal conductivity and high thermoelectric performance. The average zT value of the GCM / bismuth telluride-based composite thermoelectric material is 1.21.

[0049] Based on Bi 0.3 Sb 1.7 Te3, the present invention composites GCM, which can effectively improve the electrical conductivity of the Bi 0.3 Sb 1.7 Te3 thermoelectric material. Due to the diffusion of GCM, the carrier concentration of the composite thermoelectric material is increased. At the same time, as a magnetic second phase, GCM increases the magnetic scattering and built-in magnetic field, thereby increasing the Seebeck coefficient and making the prepared composite thermoelectric material have high electrical properties. In addition, the introduction of the GCM magnetic second phase also enhances the phonon scattering at the interface, reducing the lattice thermal conductivity of the material. Thus, the GCM / bismuth telluride-based composite thermoelectric material realizes the synergistic optimization of the electrothermal transport performance, has high electrical properties, low thermal conductivity and high thermoelectric performance.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] (1) The present invention prepares a GCM / bismuth telluride-based composite thermoelectric material by introducing Gd(Co 0.3 Sb 1.7 Te3) with Gd(Co 0.433 Mn 0.567 )2 as the magnetic second phase, optimizing the electrothermal transport performance, and the GCM / bismuth telluride-based composite thermoelectric material has high electrical and thermoelectric properties.

[0052] (2) The Gd(Co 0.433 Mn 0.567 )2 introduced in the present invention as the magnetic second phase can, on the one hand, regulate the mobility and carrier concentration through the magnetic effect (magnetic scattering and built-in magnetic field) and diffusion effect, thereby increasing the Seebeck coefficient and improving the electrical properties. On the other hand, it enhances the phonon scattering at the interface, reducing the lattice thermal conductivity and achieving the synergistic optimization of the electrothermal transport performance, so that the prepared composite thermoelectric material has high thermoelectric properties.

[0053] (3) In the temperature range of 300 - 500K, the average zT value of this composite material is increased by 39% compared with (Bi 0.3 Sb 1.7 Te3), and its average zT value is 1.21.

[0054] (4) The present invention has wide temperature range applicability and stability. When the content of GCM in the bismuth telluride matrix is 0.4wt%, at 425K, the thermoelectric figure of merit zT can reach up to 1.27 at most. Between 373 - 473K, its thermoelectric figure of merit zT is close to or not lower than 1.1, effectively solving the problem that the zT of the existing Bi2Te3-based thermoelectric material drops sharply above 400K.

[0055] (5) The process of the present invention is simple, with low requirements for experimental equipment and sites, which is conducive to large-scale and industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 is a physical diagram of a vacuum hot pressing device;

[0057] Figure 2 is the XRD pattern of the bulk samples of Examples 1 - 4 and Comparative Example 1;

[0058] Figure 3 is a schematic diagram showing the relationship between the conductivity and temperature of the bulk samples of Examples 1 - 4 and Comparative Example 1;

[0059] Figure 4 is a schematic diagram showing the relationship between the Seebeck coefficient and temperature of the bulk samples of Examples 1 - 4 and Comparative Example 1;

[0060] Figure 5 Schematic diagram of the relationship between the power factor and temperature of the bulk samples of Examples 1-4 and Comparative Example 1;

[0061] Figure 6 Schematic diagram of the relationship between the thermal conductivity and temperature of the bulk samples of Examples 1-4 and Comparative Example 1;

[0062] Figure 7 Schematic diagram of the relationship between the thermoelectric figure of merit and temperature of the bulk samples of Examples 1-4 and Comparative Example 1. Detailed implementation manners

[0063] This embodiment is implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given, but the protection scope of the present invention is not limited to the following embodiments.

[0064] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present invention are conventional reagents, methods, instruments and equipment in the art. Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0065] A GCM / bismuth telluride-based composite thermoelectric material, comprising a bismuth telluride matrix, in which a magnetic second phase GCM is compounded. The chemical formula of the bismuth telluride matrix is Bi 0.3 Sb 1.7 Te3, and the chemical formula of the GCM is Gd(Co 0.433 Mn 0.567 )2. The structural formula of the composite thermoelectric material is expressed as Gd(Co 0.433 Mn 0.567 )2 / Bi 0.3 Sb 1.7 Te3. The content of GCM in the bismuth telluride matrix is 0.3-1.0 wt%.

[0066] The preparation method of the GCM / bismuth telluride-based composite thermoelectric material includes the following steps:

[0067] S1: Mix the three elemental raw materials of Bi, Sb and Te according to the molar ratio of each element in the chemical formula of Bi 0.3 Sb 1.7 Te3, melt and prepare to obtain a Bi 0.3 Sb 1.7 Te3 ingot, and after crushing and grinding, obtain Bi 0.3 Sb 1.7 Te3 powder;

[0068] S2: According to Gd(Co 0.433 Mn 0.567)2 The molar ratio of each element in the chemical formula: Mix the three elemental raw materials of Gd, Co, and Mn, and obtain Gd(Co 0.433 Mn 0.567 )2 ingot by arc melting. Subsequently, through annealing, quenching, crushing and grinding, obtain Gd(Co 0.433 Mn 0.567 )2 powder;

[0069] S3: Mix the Gd(Co 0.433 Mn 0.567 )2 powder and Bi 0.3 Sb 1.7 Te3 powder in proportion, and grind under the protection of inert gas to prepare a uniformly mixed composite powder;

[0070] S4: Carry out vacuum hot pressing sintering on the composite powder to obtain the GCM / bismuth telluride-based composite thermoelectric material.

[0071] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0072] Example 1: 0.4wt% GCM / BST composite thermoelectric material

[0073] (1) Use Bi grains, Sb blocks and Te grains as raw materials, and then weigh 10 g of raw material particles according to the molar ratio of 0.3:1.7:3; put the raw material particles into a clean quartz tube, seal the quartz tube in advance with a sealing device and then take it out of the glove box, and connect it to the tube sealing device. After evacuating and washing the gas three times, light the hydrogen torch to heat and melt the glass plug in the quartz tube to complete the tube sealing. Put the quartz tube into a muffle furnace, set the heating rate to 2 K / min, the holding temperature to 1273 K, and the holding time to 10 h. After cooling with the furnace, obtain a BST ingot. After crushing, grinding and sieving, obtain the matrix powder of BST.

[0074] (2) Use Gd blocks, Co blocks and Mn sheets as raw materials, and then weigh 3 g of raw material particles according to the molar ratio of 1:0.866:1.134. The Mn sheet should be added 10% more on the original basis to make up for the weight loss caused by evaporation during melting. The ingot is turned over and remelted four times in an argon atmosphere to ensure uniformity. Subsequently, the obtained ingot is annealed in a vacuum quartz tube at 973 K for two weeks, and then quenched in water. After removing the surface oxide layer, the annealed ingot is crushed to obtain the GCM second-phase powder.

[0075] (3) Homogenize the BST and GCM powders. Using the GCM powder prepared in the previous two steps, weigh 0.024 g of GCM powder and 5.976 g of BST powder and mix them evenly in a high-purity argon atmosphere. Pour the mixture into a graphite mold with an inner diameter of 10 mm, and use a self-built vacuum hot-pressing equipment (HP) to sinter the powder into a block. The sintering process is as follows: the heating rate is 55 K / min, and the axial pressure is set to 7.6 kN (60 MPa). When the temperature rises to 473 K, keep it warm for about 2 minutes to evaporate the moisture in the sample and avoid cracks in the sample caused by thermal stress. Continue to heat up, the holding temperature is 673 K, and the holding time is 12 minutes to obtain a 0.4 wt% GCM / BST composite thermoelectric material.

[0076] Example 2: 0.6 wt% GCM / BST composite thermoelectric material

[0077] The difference between Example 2 and Example 1 is as follows: in step (3), weigh 0.036 g of GCM powder and 5.964 g of BST powder and mix them evenly. A 0.6 wt% GCM / BST composite thermoelectric material is prepared.

[0078] Example 3: 0.8 wt% GCM / BST composite thermoelectric material

[0079] The difference between Example 3 and Example 1 is as follows: in step (3), weigh 0.048 g of GCM powder and 5.953 g of BST powder and mix them evenly. A 0.8 wt% GCM / BST composite thermoelectric material is prepared.

[0080] Example 4: 1.0 wt% GCM / BST composite thermoelectric material

[0081] The difference between Example 4 and Example 1 is as follows: in step (3), weigh 0.06 g of GCM powder and 5.94 g of BST powder and mix them evenly. A 1.0 wt% GCM / BST composite thermoelectric material is prepared.

[0082] Comparative Example 1

[0083] (1) Using Bi grains, Sb blocks and Te grains as raw materials, then weigh 10 g of raw material particles according to a molar ratio of 0.3:1.7:3; put the raw material particles into a clean quartz tube, seal the quartz tube in advance with a sealing device and then take it out of the glove box, and connect it to the tube sealing device. After evacuating and washing the gas three times, ignite the hydrogen torch to heat and melt the glass plug in the quartz tube to complete the tube sealing. Put the quartz tube into a muffle furnace, set the heating rate to 2 K / min, the holding temperature to 1273 K, and the holding time to 10 h. After cooling with the furnace, a BST ingot is obtained, which is crushed, ground and sieved to obtain the matrix powder of BST.

[0084] (2) Sintered material: Under a high-purity argon atmosphere, approximately 6 g of the substrate powder from the previous step was poured into a graphite mold with an inner diameter of 10 mm, and the powder was sintered into a block using a self-built hot-pressing equipment (HP). The sintering process was as follows: the heating rate was 55 K / min, and the axial pressure was set to 7.6 kN (60 MPa). When the temperature reached 473 K, it was held for about 2 min to evaporate the moisture in the sample and avoid cracks in the sample caused by thermal stress. Then, the temperature was continuously increased, the holding temperature was 673 K, and the holding time was 12 min to obtain a series of BST dense bulk materials with a diameter of 10 mm and a thickness of about 10 mm.

[0085] XRD phase characterization was carried out on the GCM / BST composite thermoelectric materials prepared in Comparative Example 1 and Examples 1-4, and the XRD patterns are as Figure 2 shown. It can be seen from the figure that both the pure-phase BST sample and GCM / BST were successfully prepared.

[0086] Thermoelectric performance tests were carried out on the GCM / BST composite thermoelectric materials prepared in Comparative Example 1 and Examples 1-4, and the test results are as shown in Appendices Figure 3 、 4 、5, 6, and 7, and the specific parameter values are shown in Table 1.

[0087] It can be seen from Table 1 that the conductivity, Seebeck coefficient, and power factor of the GCM / BST composite thermoelectric materials prepared in Examples 1-4 of the present invention are all greater than those of BST in Comparative Example 1, the thermal conductivity is close to that of BST, and the thermoelectric figure of merit is higher than that of BST. Therefore, from the above data, it can be seen that the GCM / BST composite thermoelectric materials prepared by the present invention have high electrical performance, low thermal conductivity, and high thermoelectric performance.

[0088] From Figure 7 it can be seen that the GCM / BST composite thermoelectric materials prepared in Examples 1-4 of the present invention also have a high zT value even in the temperature range above 400 K. The GCM / BST composite thermoelectric material prepared in Example 1 has the best thermoelectric performance. At 425 K, the zT value can reach 1.27, and the minimum zT value between 373 and 473 K is close to or not lower than 1.1, effectively solving the problem that the zT of the existing Bi2Te3-based thermoelectric materials drops sharply above 400 K, and having wide temperature range applicability and stability.

[0089] Table 1 Thermoelectric performance parameters of Examples 1-4 and Comparative Example 1 at 425 K

[0090]

[0091]

[0092] In summary, a GCM / bismuth telluride-based composite thermoelectric material is prepared by the present invention, achieving a synergistic optimization of the electrothermal transport performance. Between 373 and 473 K, it has high electrical properties, low thermal conductivity, and high thermoelectric performance. The process is simple, with low requirements for experimental equipment and sites, facilitating large-scale and industrial production, and can be widely applied to the preparation of thermoelectric refrigeration devices.

[0093] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. Obviously, those familiar with the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative effort. 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 disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A GCM / bismuth telluride-based composite thermoelectric material, characterized in that, It includes a bismuth telluride matrix, in which a magnetic second phase GCM is compounded. The chemical formula of the bismuth telluride matrix is Bi 0.3 Sb 1.7 Te3, and the chemical formula of the GCM is Gd(Co 0.433 Mn 0.567 )2. The structural formula of the composite thermoelectric material is expressed as Gd(Co 0.433 Mn 0.567 )2 / Bi 0.3 Sb 1.7 Te3.

2. The GCM / bismuth telluride-based composite thermoelectric material according to claim 1, characterized in that, The content of GCM in the bismuth telluride matrix is 0.3-1.0 wt%.

3. The GCM / bismuth telluride-based composite thermoelectric material according to claim 2, characterized in that, The content of GCM in the bismuth telluride matrix is 0.4 wt%.

4. A method for preparing a GCM / bismuth telluride-based composite thermoelectric material according to any one of claims 1-3, characterized in that, It includes the following steps: S1: According to Bi 0.3 Sb 1.7 Mix the three elemental raw materials of Bi, Sb and Te according to the molar ratio of each element in the chemical formula of Bi 0.3 0.3 Sb 1.7 Sb 0.3 Sb 1.7 Te3 ingot, and obtain Bi 0.3 0.3 Sb 1.7 Te3 powder after crushing and grinding; S2: Mix the three elemental raw materials of Gd, Co, and Mn according to the molar ratio of each element in the chemical formula of Gd(Co 0.433 Mn 0.567 )₂, and obtain an ingot of Gd(Co 0.433 Mn 0.567 )₂ by arc melting. Subsequently, through annealing, quenching, crushing, and grinding, obtain Gd(Co 0.433 Mn 0.567 )₂ powder; S3: Mix the Gd(Co 0.433 Mn 0.567 )2 powder with Bi 0.3 Sb 1.7 Te3 powder in proportion, grind it under the protection of inert gas, and prepare a uniformly mixed composite powder; S4: Vacuum hot-press sinter the composite powder to obtain the GCM / bismuth telluride-based composite thermoelectric material.

5. The preparation method of a GCM / bismuth telluride-based composite thermoelectric material according to claim 4, wherein, In step S1, the purity of the three elemental raw materials of Bi, Sb, and Te is greater than 99.5%. The process conditions for melting are as follows: the melting temperature is 873 - 1273 K, the heating rate is 30 - 50 K / min, and the heat preservation time is 8 - 12 h. The particle size of the Bi 0.3 Sb 1.7 Te3 powder obtained after crushing and grinding is 100 - 200 μm.

6. The preparation method of a GCM / bismuth telluride-based composite thermoelectric material according to claim 4, characterized in that In step S2, the purity of the three elemental raw materials of Gd, Co and Mn is greater than 99.5%; the arc melting means melting at 1500 - 1800 °C for 3 - 5 min in an argon atmosphere, then flipping and remelting, repeating this process 3 - 5 times to obtain a Gd(Co 0.433 Mn 0.567 )2 ingot.

7. The preparation method of a GCM / bismuth telluride-based composite thermoelectric material according to claim 4, characterized in that, In step S2, the annealing means annealing the Gd(Co 0.433 Mn 0.567 )2 ingot at 773 - 1173 K for 12 - 16 days; the quenching means water quenching; the particle size of the Gd(Co 0.433 Mn 0.567 )2 powder obtained after crushing and grinding is 50 - 100 μm.

8. The preparation method of a GCM / bismuth telluride-based composite thermoelectric material according to claim 4, characterized in that In step S3, the inert gas refers to high-purity argon, the purity of the high-purity argon is 99.999%, and the particle size of the composite powder obtained after grinding is 100-200 μm.

9. The preparation method of a GCM / bismuth telluride-based composite thermoelectric material according to claim 4, characterized in that, In step S4, the vacuum hot-press sintering is carried out in a vacuum hot-press equipment, and the process conditions of the vacuum hot-press sintering are: the sintering temperature is 623-673 K, the axial pressure is 45-60 MPa, the heating rate is 30-50 K / min, and the heat preservation is 10-14 min.

10. Application of a GCM / bismuth telluride-based composite thermoelectric material according to any one of claims 1-3 in a thermoelectric refrigeration device.

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