GeTe-based / SiC high-entropy composite thermoelectric ceramic and preparation method thereof

Abstract

The invention provides GeTe-based / SiC high-entropy composite thermoelectric ceramic and a preparation method thereof, belongs to the technical field of composite materials, and aims to solve the problem of poor thermoelectric performance of materials. The thermoelectric performance of the material is improved by adopting the design that the high-entropy material is combined with the material composite structure. The preparation method comprises the following steps: firstly, preparing Ge < 1-0.2 x > Ag < 0.2 x > Bi < 0.2 x > Pb < 0.2 x > Sb < 0.2 x > Te < 1-y > Se < y > high-entropy thermoelectric nano powder (0.02 lt; x is less than or equal to 0.15, 0.1 lt; y < = 0.3); and obtaining the GeTe-based / SiC high-entropy composite thermoelectric ceramic by using an oscillation pressure sintering method. The GeTe-based / SiC high-entropy composite thermoelectric ceramic prepared by the invention has relatively high thermoelectric performance, and the maximum ZT value reaches 1.35. The GeTe-based / SiC high-entropy composite thermoelectric ceramic prepared by the method can be used in the fields of refrigeration of integrated circuit chips, refrigeration of light emitting diodes and light detectors and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic materials, and particularly relates to a high-performance thermoelectric composite ceramic. Background Art

[0002] Due to its unique direct thermal-electric conversion characteristics, thermoelectric conversion materials have shown broad application prospects in the power supply systems of deep space detectors, energy supply modules of flexible wearable devices, geothermal power generation devices, and industrial waste heat recovery. However, there are complex mutual constraints among the thermoelectric performance parameters (Seebeck coefficient S, electrical conductivity σ, thermal conductivity κ) of the materials, resulting in significant challenges in improving the thermoelectric figure of merit. On the premise of a determined energy band structure, the key to achieving a breakthrough in the zT value lies in precisely regulating the balance relationship among the carrier concentration (n), carrier mobility (μ), and lattice thermal conductivity (κL).

[0003] Currently, the optimization of thermoelectric materials mainly adopts a heavy doping strategy. Although it can effectively adjust the carrier concentration and reduce the lattice thermal conductivity, excessive doping atoms will introduce strong point defect scattering centers, significantly reducing the carrier mobility. In contrast, low-concentration doping has less impact on the carrier transport characteristics, but it is difficult to achieve the co-optimization of the carrier concentration and the lattice thermal conductivity. Therefore, developing a new type of dilute doping control technology to maximize the retention of carrier mobility while achieving the optimization of carrier concentration and the suppression of lattice thermal conductivity has become a key scientific issue in improving the zT value of thermoelectric materials.

[0004] GeTe-based thermoelectric materials have good electrical properties, but their high thermal conductivity limits the further improvement of their thermoelectric performance. Patent Publication No. CN 111592357 A discloses a germanium telluride-based thermoelectric material with high structural stability and high thermoelectric performance and its preparation method. The chemical general formula of the germanium telluride-based thermoelectric material is Ge 1-x-y-z M 2x N y Mn z Te, where M is an element of Cu or Ag, N is an element of Sb or Bi, 0 < x ≤ 0.03, 0 < y ≤ 0.1, 0 < z ≤ 0.2. This patent improves the thermoelectric performance by atomic doping, but still has the above problems. Summary of the Invention

[0005] Aiming at the problem of low performance of thermoelectric ceramics, the present invention proposes a GeTe-based / SiC high-entropy composite thermoelectric ceramic and its preparation method. The prepared GeTe-based / SiC high-entropy composite thermoelectric ceramic has good thermoelectric performance.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A preparation method of GeTe-based / SiC high-entropy composite thermoelectric ceramics, characterized by comprising the following steps:

[0008] (1) First, prepare high-entropy thermoelectric material Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y nano-powders, 0.02 < x ≤ 0.15, 0.1 < y ≤ 0.3;

[0009] (2) Mix and ball-mill the high-entropy thermoelectric nano-powders of Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y with SiC powder, and then press into a sheet to obtain a ceramic sheet;

[0010] (3) Sinter the ceramic sheet to prepare GeTe-based / SiC high-entropy composite thermoelectric ceramics.

[0011] The steps for the high-entropy thermoelectric material Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y are as follows: Calculate and weigh the raw material powders Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, Na2Se according to the stoichiometric ratio, disperse and dissolve them with the basic reagent and the morphology regulator in the solvent, and then carry out microwave hydrothermal reaction.

[0012] The mass ratio of the raw material powder, the morphology regulator, the basic reagent and the solvent is 1:(1 - 1.3):(1 - 1.7):(2.4 - 2.9).

[0013] The morphology regulator is polyvinylpyrrolidone; the basic reagent is sodium hydroxide; the solvent is water and / or ethanol.

[0014] The temperature of the microwave hydrothermal reaction is 235 - 250 °C, the time is 600 - 850 min, the microwave heating frequency is 2450 MHz, and the microwave power is 1000 - 1350 W.

[0015] In the step (2), the content of SiC in Ge 1-0.2x Ag 0.2x Bi 0.2x Pb0.2x Sb 0.2x Te 1-y Se y 0.5 - 2.5% of the sum of the masses of

[0016] In step (2), SiC accounts for 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y 1 - 2% of the sum of the masses of

[0017] The sintering is vibration pressure sintering.

[0018] The vibration pressure sintering method is as follows: Place the ceramic sheet into a vibration pressure sintering furnace. When the temperature in the furnace is below 300 °C, the heating rate is 3 - 5 °C / min, the pressure in the furnace is increased to 22 - 25 MPa, and it is kept at 300 °C for 100 - 200 min; then the temperature is raised to 350 - 420 °C, the heating rate is 1 - 2 °C / min, and on the basis of the pressure of 22 - 25 MPa, a vibration pressure of 25 - 35 MPa is applied, the vibration frequency is 1 - 3 Hz, and it is kept at temperature for 50 - 180 min; then the vibration pressure is unloaded, a constant pressure of 22 - 25 MPa is maintained, and it is cooled at a cooling rate of 1 - 3 °C / min. When the temperature in the furnace cools to 200 - 260 °C, the constant pressure is unloaded, and after cooling to room temperature, it is taken out to obtain the GeTe - based / SiC high - entropy composite thermoelectric ceramic.

[0019] Advantages of the present invention: The present invention improves the performance of the composite thermoelectric ceramic by using the high - entropy ceramic method in combination with the second - phase composite method. On the one hand, the electrical properties of the GeTe - based thermoelectric ceramic material are improved by doping with high - entropy ceramics. The high - entropy ceramic material can promote the transformation of its crystal structure from low symmetry to high symmetry, thereby increasing the energy - level degeneracy, and thus obtaining a high effective mass of the density of states and a high Seebeck coefficient. At the same time, it can also increase the lattice distortion degree of the thermoelectric material and reduce its thermal conductivity. On the other hand, introducing SiC nano - powder increases phonon scattering and reduces the thermal conductivity of the composite ceramic, thereby further improving its thermoelectric performance. Moreover, a high - density and nano - sized composite thermoelectric ceramic is obtained by using the vibration pressure sintering process. The above processes act synergistically to improve the performance of the GeTe - based / SiC high - entropy composite thermoelectric ceramic. The prepared composite ceramic has a high thermoelectric figure of merit. The GeTe - based / SiC high - entropy composite thermoelectric ceramic prepared by this method has the advantages of low cost, nano - sized particles, and excellent thermoelectric performance. The maximum ZT value reaches 1.35, showing good application prospects in the fields of refrigeration of integrated circuit chips, refrigeration of photodetectors, etc. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0021] Figure 1 SEM image of the high-entropy composite thermoelectric ceramic prepared for Example 1.

[0022] Figure 2 Thermal conductivity graph of the high-entropy composite thermoelectric ceramic prepared for different examples at 500 °C.

[0023] Figure 3 Thermoelectric figure of merit graph of the high-entropy composite thermoelectric ceramic prepared for different examples at 500 °C. Detailed implementation manners

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

[0025] Example 1

[0026] A GeTe-based / SiC high-entropy composite thermoelectric ceramic and its preparation method are as follows:

[0027] (1) Preparation of Ge by microwave hydrothermal method 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y Process for preparing high-entropy thermoelectric nanometer powder (x = 0.02, y = 0.01) nanometer powder is as follows: Calculate and weigh Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, and Na2Se according to the stoichiometric ratio. Then, mix the raw materials, polyvinyl alcohol, KOH, and water in a mass ratio of 1:1:1:2.4, stir well, and then transfer to a hydrothermal reaction kettle and place it in a microwave reactor for reaction. The heating rate of the microwave reactor is 1 °C / min, the temperature of the microwave hydrothermal reaction is 235 °C, and the time is 850 min. The microwave heating frequency is 2450 MHz, and the microwave power is 1000 W. Then take out the sample, immediately wash and dry the sample with deionized water and alcohol, and initially obtain the prepared Ge1- 0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High-entropy thermoelectric nano-powders.

[0028] (2) Mix the nano-powders using a ball mill: Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The mass percentage content of the high-entropy thermoelectric nano-powders is 97.5%, and the mass percentage content of the SiC is 2.5%. Mix the above powders using a ball mill and perform tabletting using the traditional ceramic tabletting process.

[0029] (3) Prepare the Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramics. Place the composite thermoelectric ceramics that have been tableted using the traditional ceramic tabletting process into an oscillating pressure sintering furnace. When the temperature in the furnace is below 300°C, the heating rate is 3°C / min, and the pressure in the furnace is increased to 22 MPa and held at 300°C for 100 min; then raise the temperature to 350°C at a heating rate of 1°C / min, start applying an oscillating pressure of 25 MPa on the basis of the 22 MPa pressure, the oscillation frequency is 1 Hz, and hold for 180 min; then unload the oscillating pressure, maintain a constant pressure of 22 MPa, and cool at a cooling rate of 1°C / min. When the temperature in the furnace cools to 200°C, unload the constant pressure, take it out after cooling to room temperature, and obtain the GeTe-based / SiC high-entropy composite thermoelectric ceramics.

[0030] Example 2

[0031] A GeTe-based / SiC high-entropy composite thermoelectric ceramic and its preparation method are as follows:

[0032] (1) Prepare Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se yThe process of high entropy thermoelectric nanopowder (x=0.15, 0.y=0.3) nanopowder is as follows: Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, Na2Se are calculated and weighed according to the stoichiometric ratio, and then the raw materials, polyvinyl alcohol, KOH, and water are mixed in a mass ratio of 1:1.3:1.7:2.9. After sufficient stirring, they are transferred into a hydrothermal reactor and placed in a microwave reactor for reaction. The heating rate of the microwave reactor is 3°C / min, the temperature of the microwave hydrothermal reaction is 250°C, and the time is 600min. The microwave heating frequency is 2450MHz, and the microwave power is 1350W. After that, the sample is taken out, and the sample is immediately washed and dried with deionized water and alcohol to obtain the initial preparation of Ge 1- 0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High entropy thermoelectric nanopowders.

[0033] (2) Use a ball mill to mix the above nanopowders: Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The mass percentage of the high entropy thermoelectric nano powder is 99.5%, and the mass percentage of the SiC is 0.5%. The above powders are mixed by ball milling and pressed into tablets by conventional ceramic tableting technology.

[0034] (3) Preparation of Ge by oscillating pressure sintering 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramics, the composite thermoelectric ceramics formed by pressing using a traditional ceramic pressing process are placed in an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300°C, the heating rate is 5°C / min, the pressure in the furnace is increased to 25MPa, and it is kept at 300°C for 200min; then the temperature is increased to 420°C at a heating rate of 2°C / min, and an oscillating pressure of 35MPa is applied on the basis of a pressure of 25MPa, with an oscillation frequency of 3Hz, and the heat is kept for 180min; then the oscillating pressure is unloaded, a constant pressure of 25MPa is maintained, and it is cooled at a cooling rate of 3°C / min. When the temperature in the furnace is cooled to 260°C, the constant pressure is unloaded, and it is taken out after cooling to room temperature to obtain GeTe-based / SiC high entropy composite thermoelectric ceramics.

[0035] Example 3

[0036] A GeTe-based / SiC high-entropy composite thermoelectric ceramic and a preparation method thereof, the steps are as follows:

[0037] (1) Preparation of Ge by microwave hydrothermal method 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The process of high entropy thermoelectric nanopowder (x=0.15, y=0.2) nanopowder is as follows: Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, Na2Se are calculated and weighed according to the stoichiometric ratio, and then the raw materials, polyvinyl alcohol, KOH, and water are mixed in a mass ratio of 1:1.2:1.5:2.5. After sufficient stirring, they are transferred into a hydrothermal reactor and placed in a microwave reactor for reaction. The heating rate of the microwave reactor is 2°C / min, the temperature of the microwave hydrothermal reaction is 240°C, and the time is 700min. The microwave heating frequency is 2450MHz, and the microwave power is 1250W. After that, the sample is taken out, and the sample is immediately washed and dried with deionized water and alcohol to obtain the initial preparation of Ge 1- 0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High entropy thermoelectric nanopowders.

[0038] (2) Use a ball mill to mix the above nanopowders: Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The mass percentage of the high entropy thermoelectric nano powder is 98%, and the mass percentage of the SiC is 2%. The above powders are mixed by ball milling and pressed into tablets by conventional ceramic tableting technology.

[0039] (3) Preparation of Ge by oscillating pressure sintering 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramics, the composite thermoelectric ceramics formed by pressing using a traditional ceramic pressing process are placed in an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300°C, the heating rate is 4°C / min, the pressure in the furnace is increased to 23MPa, and it is kept at 300°C for 150min; then the temperature is increased to 390°C at a heating rate of 1.5°C / min, and an oscillating pressure of 28MPa is applied on the basis of a pressure of 23MPa, with an oscillation frequency of 2Hz, and the heat is kept for 120min; then the oscillating pressure is unloaded, a constant pressure of 23MPa is maintained, and it is cooled at a cooling rate of 2°C / min. When the temperature in the furnace is cooled to 240°C, the constant pressure is unloaded, and it is taken out after cooling to room temperature to obtain GeTe-based / SiC high entropy composite thermoelectric ceramics.

[0040] Example 4

[0041] A GeTe-based / SiC high-entropy composite thermoelectric ceramic and a preparation method thereof, the steps are as follows:

[0042] (1) Preparation of Ge by microwave hydrothermal method 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The process of high entropy thermoelectric nanopowder (x=0.05, y=0.12) nanopowder is as follows: Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, Na2Se are calculated and weighed according to the stoichiometric ratio, and then the raw materials, polyvinyl alcohol, KOH, and water are mixed in a mass ratio of 1:1.25:1.6:2.7. After sufficient stirring, they are transferred to a hydrothermal reactor and placed in a microwave reactor for reaction. The heating rate of the microwave reactor is 2.5℃ / min, the temperature of the microwave hydrothermal reaction is 248℃, and the time is 750min. The microwave heating frequency is 2450MHz, and the microwave power is 1300W. After that, the sample is taken out, and the sample is immediately washed and dried with deionized water and alcohol to obtain the preliminary preparation of Ge 1- 0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High entropy thermoelectric nanopowders.

[0043] (2) Use a ball mill to mix the above nanopowders: Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te1-y Se y The mass percentage of the high-entropy thermoelectric nanometer powder is 98.5%, and the mass percentage of the SiC is 1.5%. The above powders are mixed by ball milling and then tableted by the traditional ceramic tablet pressing process.

[0044] (3) Prepare Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramics. Place the composite thermoelectric ceramics tableted by the traditional ceramic tablet pressing process into an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3.5 °C / min, and the pressure in the furnace is increased to 24 MPa and held at 300 °C for 160 min; then raise the temperature to 410 °C at a heating rate of 1.8 °C / min. Based on the pressure of 24 MPa, start to apply an oscillating pressure of 33 MPa, the oscillation frequency is 2.5 Hz, and hold for 130 min; then unload the oscillating pressure, maintain a constant pressure of 24 MPa, and cool at a cooling rate of 1.8 °C / min. When the temperature in the furnace cools to 240 °C, unload the constant pressure, take it out after cooling to room temperature, and obtain GeTe-based / SiC high-entropy composite thermoelectric ceramics.

[0045] Example 5

[0046] A GeTe-based / SiC high-entropy composite thermoelectric ceramic and its preparation method are as follows:

[0047] (1) Prepare Ge by microwave hydrothermal method 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The process of the high-entropy thermoelectric nanometer powder (x = 0.13, 0.y = 0.18) is as follows: Calculate and weigh Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, and Na2Se according to the stoichiometric ratio. Then, mix the raw materials, polyvinyl alcohol, KOH, and water in a mass ratio of 1:1.15:1.35:2.65, stir well, and then transfer to a hydrothermal reaction kettle and place it in a microwave reactor for reaction. The heating rate of the microwave reactor is 2.5 °C / min, the temperature of the microwave hydrothermal reaction is 248 °C, and the time is 820 min. The microwave heating frequency is 2450 MHz, and the microwave power is 1150 W. Then take out the sample, immediately wash and dry the sample with deionized water and alcohol, and initially obtain Ge1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High-entropy thermoelectric nano-powders.

[0048] (2) Mix the above nano-powders using a ball mill: Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The mass percentage of the high-entropy thermoelectric nano-powders is 99%, and the mass percentage of the SiC is 1%. Mix the above powders using a ball mill and perform tableting using the traditional ceramic tableting process.

[0049] (3) Prepare the Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramics. Place the composite thermoelectric ceramics tableted using the traditional ceramic tableting process into an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3.8 °C / min, and the pressure in the furnace is increased to 24 MPa and held at 300 °C for 180 min; then raise the temperature to 390 °C at a heating rate of 2 °C / min, start applying an oscillating pressure of 34 MPa on the basis of the 24 MPa pressure, the oscillation frequency is 2.5 Hz, and hold for 170 min; then unload the oscillating pressure, maintain a constant pressure of 24 MPa, and cool at a cooling rate of 2.5 °C / min. When the temperature in the furnace cools to 220 °C, unload the constant pressure, take it out after cooling to room temperature, and obtain the GeTe-based / SiC high-entropy composite thermoelectric ceramics.

[0050] Figure 1 For the Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y / SiC composite thermoelectric ceramic cross-section SEM image. The composite material grains are dense.

[0051] Figure 2 For the Ge 1-0.2x Ag 0.2x Bi0.2x Pb 0.2x Sb 0.2x Te 1-y Se y Thermal conductivity graph of Ge

[0052] Figure 3 Ge prepared for Examples 1, 2, 3, 4, and 5 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y Thermoelectric figure of merit graph of Ge

[0053] Comparative Example 1

[0054] A GeTe thermoelectric ceramic, the preparation method steps are as follows:

[0055] (1) Prepare GeTe thermoelectric nano powder by microwave hydrothermal method, the process is as follows: Weigh GeO2 and Na2Te raw materials with a molar ratio of 1:1, then transfer the raw materials, polyvinyl alcohol, KOH, and water in a mass ratio of 1:1:1:2.4, stir well, and then transfer to a hydrothermal reaction kettle and place it in a microwave reactor for reaction. The heating rate of the microwave reactor is 1 °C / min, the temperature of the microwave hydrothermal reaction is 235 °C, and the time is 850 min. The microwave heating frequency is 2450 MHz, and the microwave power is 1000 W. Then take out the sample, immediately wash and dry the sample with deionized water and alcohol to initially obtain GeTe thermoelectric nano powder.

[0056] (2) Press and form the GeTe thermoelectric nano powder by using the traditional ceramic pressing process.

[0057] (3) Place the pressed ceramic sheet into an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3 °C / min, the pressure in the furnace is increased to 22 MPa, and it is kept at 300 °C for 100 min; then the temperature is increased to 350 °C, the heating rate is 1 °C / min, and an oscillating pressure of 25 MPa is applied on the basis of 22 MPa pressure, the oscillation frequency is 1 Hz, and it is kept warm for 180 min; then unload the oscillating pressure, keep the constant pressure of 22 MPa, and cool at a cooling rate of 1 °C / min. When the temperature in the furnace cools to 200 °C, unload the constant pressure, take it out after cooling to room temperature to obtain GeTe thermoelectric ceramic. After testing, the thermal conductivity of GeTe thermoelectric ceramic at 500 °C is 1.41, and the maximum figure of merit is 0.65.

[0058] Comparative Example 2

[0059] A GeTe-based high-entropy thermoelectric ceramic, and the preparation method steps are as follows:

[0060] (1) Preparation of Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y The process of high-entropy thermoelectric nano-powder (x = 0.02, y = 0.01) is as follows: Calculate and weigh Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, and Na2Se according to the stoichiometric ratio. Then, mix the raw materials, polyvinyl alcohol, KOH, and water in a mass ratio of 1:1:1:2.4, stir well, and then transfer them to a hydrothermal reaction kettle and place it in a microwave reactor for reaction. The heating rate of the microwave reactor is 1 °C / min, the temperature of the microwave hydrothermal reaction is 235 °C, and the time is 850 min. The microwave heating frequency is 2450 MHz, and the microwave power is 1000 W. After that, take out the sample, immediately wash and dry the sample with deionized water and alcohol to initially obtain Ge 1- 0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High-entropy thermoelectric nano-powder.

[0061] (2) Press and form the Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y High-entropy thermoelectric nano-powder by using the traditional ceramic pressing process.

[0062] (3) Prepare Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se yFor the thermoelectric ceramics, the composite thermoelectric ceramics formed by pressing using the traditional ceramic pressing process are placed into an oscillating pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3 °C / min, the pressure in the furnace is increased to 22 MPa, and it is kept at 300 °C for 100 min. Subsequently, the temperature is increased to 350 °C at a heating rate of 1 °C / min. Based on the 22 MPa pressure, an oscillating pressure of 25 MPa is applied, the oscillation frequency is 1 Hz, and it is kept at this temperature for 180 min. Then, the oscillating pressure is unloaded, the constant pressure of 22 MPa is maintained, and it is cooled at a cooling rate of 1 °C / min. When the temperature in the furnace cools to 200 °C, the constant pressure is unloaded, and after cooling to room temperature, it is taken out to obtain the GeTe-based high-entropy thermoelectric ceramics. After testing, the thermal conductivity of the GeTe-based high-entropy thermoelectric ceramics at 500 °C is 1.25, and the maximum figure of merit is 0.89.

[0063] Comparative Example 3

[0064] A GeTe / SiC composite thermoelectric ceramic and its preparation method are as follows:

[0065] (1) Prepare GeTe thermoelectric nanometer powder by microwave hydrothermal method, and the process is as follows: Weigh the raw materials of GeO2 and Na2Te with a molar ratio of 1:1. Then, the raw materials, polyvinyl alcohol, KOH, and water are in a mass ratio of 1:1:1:2.4. After fully stirring, it is transferred to a hydrothermal reaction kettle and placed in a microwave reactor for reaction. The heating rate of the microwave reactor is 1 °C / min, the temperature of the microwave hydrothermal reaction is 235 °C, and the time is 850 min. The microwave heating frequency is 2450 MHz, and the microwave power is 1000 W. Then, the sample is taken out, immediately washed with deionized water and alcohol and dried to initially obtain the GeTe thermoelectric nanometer powder.

[0066] (2) Mix the nanometer powder using a ball mill: The mass percentage content of the GeTe thermoelectric nanometer powder is 97.5%, and the mass percentage content of the SiC is 2.5%. The above powders are mixed using a ball mill and pressed into a sheet using the traditional ceramic pressing process.

[0067] (3) Preparation of GeTe / SiC composite thermoelectric ceramics by using oscillatory pressure sintering method: Place the composite thermoelectric ceramics formed by pressing using the traditional ceramic pressing process into an oscillatory pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3 °C / min, the pressure in the furnace is increased to 22 MPa, and it is kept at 300 °C for 100 min; then the temperature is raised to 350 °C, the heating rate is 1 °C / min, and an oscillatory pressure of 25 MPa is applied on the basis of a pressure of 22 MPa, the oscillation frequency is 1 Hz, and it is kept at this temperature for 180 min; then the oscillatory pressure is unloaded, a constant pressure of 22 MPa is maintained, and it is cooled at a cooling rate of 1 °C / min. When the temperature in the furnace is cooled to 200 °C, the constant pressure is unloaded, and after cooling to room temperature, it is taken out to obtain GeTe / SiC high-entropy composite thermoelectric ceramics. After testing, the thermal conductivity of the GeTe-based high-entropy thermoelectric ceramics at 500 °C is 1.1, and the maximum figure of merit is 0.76.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of GeTe-based / SiC high-entropy composite thermoelectric ceramics, characterized in that, It includes the following steps: (1) First, prepare high-entropy thermoelectric material Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y nano-powders, where 0.02 < x ≤ 0.15 and 0.1 < y ≤ 0.3; (2) Mix the high-entropy thermoelectric nanometer powder and SiC powder by ball milling, and then press them into tablets to obtain ceramic wafers; 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y Mix the high-entropy thermoelectric nanometer powder and SiC powder by ball milling, and then press them into tablets to obtain ceramic wafers; (3) The ceramic sheet is sintered to prepare GeTe-based / SiC high-entropy composite thermoelectric ceramics.

2. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 1, characterized in that, The high-entropy thermoelectric material Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y is prepared as follows: Calculate and weigh the raw material powders Bi(NO3)3, AgNO3, Pb(NO3)2, GeO2, Sb2O3, Na2Te, and Na2Se according to the stoichiometric ratio, disperse and dissolve them together with the basic reagent and the morphology regulator in a solvent, and then carry out a microwave hydrothermal reaction.

3. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 2, wherein, The mass ratio of the raw material powder, the morphology regulator, the alkaline reagent and the solvent is 1:(1 - 1.3):(1 - 1.7):(2.4 - 2.9).

4. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 3, wherein The morphology regulator is polyvinylpyrrolidone; the alkaline reagent is sodium hydroxide; the solvent is water and / or ethanol.

5. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 4, wherein The temperature of the microwave hydrothermal reaction is 235 - 250 °C, the time is 600 - 850 min, the microwave heating frequency is 2450 MHz, and the microwave power is 1000 - 1350 W.

6. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to any one of claims 1-5, characterized in that, In step (2), SiC accounts for 0.5-2.5% of the sum of the masses of Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y and SiC 7. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 6, characterized in that In the step (2), SiC accounts for 1-2% of the sum of the masses of Ge 1-0.2x Ag 0.2x Bi 0.2x Pb 0.2x Sb 0.2x Te 1-y Se y and SiC 8. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 1, wherein, The sintering is vibration pressure sintering.

9. The preparation method of the GeTe-based / SiC high-entropy composite thermoelectric ceramic according to claim 8, characterized in that, The vibration pressure sintering method is as follows: Place the ceramic sheet into a vibration pressure sintering furnace. When the temperature in the furnace is lower than 300 °C, the heating rate is 3 - 5 °C / min, and the pressure in the furnace is increased to 22 - 25 MPa, and it is kept at 300 °C for 100 - 200 min; then the temperature is raised to 350 - 420 °C, the heating rate is 1 - 2 °C / min, and on the basis of the pressure of 22 - 25 MPa, a vibration pressure of 25 - 35 MPa is applied, the vibration frequency is 1 - 3 Hz, and it is kept warm for 50 - 180 min; then the vibration pressure is unloaded, and a constant pressure of 22 - 25 MPa is maintained, and it is cooled at a cooling rate of 1 - 3 °C / min. When the temperature in the furnace cools to 200 - 260 °C, the constant pressure is unloaded, and after cooling to room temperature, it is taken out to obtain GeTe-based / SiC high-entropy composite thermoelectric ceramics.

10. GeTe-based / SiC high-entropy composite thermoelectric ceramics prepared by the method according to any one of claims 1 - 9.

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