P-type Bi0. 5Sb1. 5Te3-based thermoelectric material, thermoelectric refrigeration device and preparation method and application of thermoelectric refrigeration device

Abstract

The invention relates to a p-type Bi < 0.5 > Sb < 1.5 > Te < 3 >-based thermoelectric material, a thermoelectric refrigeration device and a preparation method and application thereof, the chemical formula of the p-type Bi < 0.5 > Sb < 1.5 > Te < 3-x > Te < 3-x > Ix is Bi < 0.5 > Sb < 1.5 > Te < 3-x > Ix, and x is greater than or equal to 0 and less than or equal to 0.01. According to the invention, high-purity elementary substances Bi, Sb and Te and a binary compound TeI4 are used as raw materials, a high-orientation Bi0. 5Sb1. 5Te3-based thermoelectric material is obtained through a gradient growth method, and a thermoelectric refrigeration device is further prepared. Compared with the prior art, the thermoelectric material disclosed by the invention obtains lower carrier concentration, the temperature corresponding to a zT peak value (-1.1) is shifted to 315K, the thermoelectric performance (average zT-0. 8) in a low-temperature range of 180K-300K is optimized, and correspondingly, the maximum refrigeration temperature difference of a refrigeration device is improved.

Description

Technical Field

[0001] The present invention relates to the field of thermoelectric refrigeration technology, in particular to a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials, thermoelectric refrigeration devices, and preparation methods and applications thereof. Background Art

[0002] Low-temperature thermoelectric materials and refrigeration devices have broad application prospects in the fields of medicine, aerospace, electronic equipment, and heat recovery. For example, in superconducting electronics, superconducting materials require a low-temperature environment to work properly, and low-temperature thermoelectric refrigeration technology is also expected to provide the required reliable low-temperature environment for superconducting materials. Therefore, the research and development of efficient and stable low-temperature thermoelectric materials and refrigeration devices will promote technological innovation and industrial development in these fields. The cooling capacity of advanced thermoelectric devices depends largely on the performance of the materials. Excellent performance requires a high dimensionless thermoelectric figure of merit zT=S 2 Τ / ρ(κ ele +κ lat ), where S, ρ, T, κ ele , κ lat They are Seebeck coefficient, resistivity, absolute temperature, electronic thermal conductivity and lattice thermal conductivity. c With hot end T h Maximum temperature difference ΔT max Depends on the material’s zT, which can be approximated as ΔT max =0.5zT c 2 .

[0003] Bi2Te3 materials have been the best candidates in their class since semiconductors were considered the most promising materials for thermoelectric cooling in the 1950s. However, in the past two decades, Bi2Te3-based thermoelectric materials have been focused on improving performance in the temperature range above near room temperature, and there has been very little research on the performance of commercial bismuth telluride below room temperature. Currently, the thermoelectric figures of merit of commercial p-type and commercial n-type bismuth telluride materials are 1.0 (T = 350K) and 0.8 (T = 320K), respectively. The cooling temperature difference of commercial bismuth telluride devices has almost stagnated due to the lack of attention paid to material properties for a long time. Therefore, there are still many scientific problems to be explored. It is worth looking forward to that a large number of physical foundations and experimental studies of near-room temperature bismuth telluride-based thermoelectric semiconductors have also provided a wealth of feasible strategies for their low-temperature performance research. Therefore, it is expected that the low-temperature thermoelectric performance of bismuth telluride-based materials will be further optimized and the cooling temperature difference of thermoelectric devices will be improved.

[0004] The peak value of the thermoelectric figure of merit of p-type bismuth telluride thermoelectric materials in existing commercial technologies appears at 350K, and decreases with decreasing temperature below 350K, resulting in low performance below room temperature, limiting the cooling capacity of existing thermoelectric cooling devices below room temperature. Currently, little attention has been paid to the cooling research of bismuth telluride materials to move the peak temperature of the thermoelectric figure of merit below 350K to improve the low-temperature thermoelectric performance of p-type bismuth telluride and the cooling capacity of the device. Summary of the invention

[0005] The purpose of the present invention is to provide a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials, thermoelectric refrigeration devices, and preparation methods and applications thereof. The prepared thermoelectric materials have excellent thermoelectric refrigeration performance at room temperature and below.

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

[0007] In one aspect, the present invention provides a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, the p-type Bi 0.5 Sb 1.5 The chemical formula of Te3-based thermoelectric materials is Bi 0.5 Sb 1.5 Te 3-x I x , where 0≤x≤0.01.

[0008] Preferably, the Bi 0.5 Sb 1.5 Te3-based thermoelectric materials show a high degree of orientation in the (00l) crystal plane direction.

[0009] Preferably, the Bi 0.5 Sb 1.5 Te3-based thermoelectric materials are crystalline materials with high orientation.

[0010] Preferably, the Bi 0.5 Sb 1.5 Te 3-x I x In the equation, x represents the molar fraction of doped I.

[0011] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I x Medium, 0 <x≤0.01。

[0012] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I x0.003≤x≤0.006, when x is in this range, the material has a lower carrier concentration, better electrical properties and lower thermal properties at low temperatures.

[0013] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I x In the case of x = 0.0045, the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials have a better carrier concentration in the temperature range of 180K to 300K, so they are more capable of moving the zT peak to a lower temperature and the average zT is the highest in the range of 180K to 300K.

[0014] Preferably, the p-type Bi 0.5 Sb 1.5 The carrier concentration of Te3-based thermoelectric materials is 2.5×10 19 ~1.0×10 19 cm -3 .

[0015] Preferably, the p-type Bi 0.5 Sb 1.5 The pF peak value of Te3-based thermoelectric materials is 50-60 μW cm -1 K -2 , the corresponding peak temperature is between 250K and 150K.

[0016] Preferably, the p-type Bi 0.5 Sb 1.5 The zT peak of Te3-based thermoelectric materials is 1.0~1.2, and the corresponding peak temperature is at 350K~300K.

[0017] Preferably, the p-type Bi 0.5 Sb 1.5 The average zT of Te3-based thermoelectric materials in the low temperature range of 180K to 300K is 0.75 to 0.85.

[0018] In a second aspect, the present invention also provides a p-type Bi 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material comprises the following steps:

[0019] S1. Raw material preparation: weigh the single substances Bi, Sb, Te and binary compound TeI4 raw materials according to the stoichiometric ratio;

[0020] S2. Loading and packaging: Put the weighed TeI4, Te, Bi, and Sb raw materials into a quartz tube in sequence, evacuate the tube, and then use a hydrogen-oxygen flame gun to perform vacuum packaging;

[0021] S3, melt quenching: heating the quartz tube containing the single element raw material to make the raw material react in a molten state, and then quenching it into water to obtain a material ingot;

[0022] S4, gradient growth: Put the quartz tube containing the material ingot obtained in S3 into a vertical temperature gradient furnace, and use the vertical temperature gradient growth method to prepare Bi 0.5 Sb 1.5 Te3-based thermoelectric materials.

[0023] Preferably, in step S1, when the single substance Te is weighed, the mass of the single substance Te exceeds the mass of Bi 0.5 Sb 1.5 Te 3-x I x The stoichiometric ratio of each element in the mixture is calculated to be 2 to 4 wt% to compensate for the volatilization of Te element at high temperature.

[0024] Preferably, in step S1, the total mass of the raw materials of the target crystal is 20-50 g.

[0025] Preferably, in step S2, the vacuum degree in the quartz tube is 10 -3 ~10 0 pa.

[0026] Further preferably, in step S2, the vacuum degree in the quartz tube is 8×10 -1 pa.

[0027] Preferably, in step S3, the heating process conditions are: heating from room temperature to 690-710°C at a rate of 150-200°C per hour, and keeping at the melting temperature for 6-10 hours to allow the raw materials to be fully reacted in a molten state.

[0028] Preferably, in step S4, the process conditions of the vertical temperature gradient growth method are: the temperature gradient in the crystal growth region is 6-10° C. / cm, more preferably 8° C. / cm.

[0029] Preferably, in step S4, the process conditions of the vertical temperature gradient growth method are: heating the molten ingot at a temperature of 690-710°C until it is fully melted, and then cooling it to 620-680°C at a rate of 20-35K / hour; using 620-680°C as the initial growth temperature, cooling it to 470-550°C at a rate of 1-3K / hour, and then cooling it with the furnace.

[0030] Further preferably, in step S4, the process conditions of the vertical temperature gradient growth method are: 640-660°C as the initial growth temperature, setting the cooling rate to 1.5-2.5K / hour, cooling to 500-520°C and then cooling with the furnace.

[0031] Further preferably, in step S4, the crystal growth is Bi 0.5 Sb 1.5 During the growth process of Te3-based thermoelectric materials, the materials and the furnace body are in a relatively static state.

[0032] The present invention aims to improve the low-temperature performance of p-type bismuth telluride materials and verify the improved effect achieved through actual refrigeration devices.

[0033] In a third aspect, the present invention further provides a thermoelectric cooling device, comprising the above-mentioned p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 Thermoelectric material, wherein the p-type Bi 0.5 Sb 1.5 The Te3-based thermoelectric material is the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials.

[0034] Preferably, the thermoelectric cooling device is a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials as p-type legs of thermoelectric cooling devices, based on commercial n-type Bi2Te 2.79 Se 0.21 As the n-leg of the thermoelectric cooling device.

[0035] Preferably, the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials serve as the p-type leg of the thermoelectric cooling device, which improves the maximum cooling temperature difference of the thermoelectric cooling device when the hot end temperature is 180K~300K.

[0036] In a fourth aspect, the present invention further provides a method for preparing the above-mentioned thermoelectric refrigeration device, comprising the following steps:

[0037] SS1. Theoretical simulation: Comsol software is used to simulate the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 The theoretical optimal size of the legs of the thermoelectric cooling device when the materials match;

[0038] SS2, size cutting: according to the theoretical optimal size of the thermoelectric cooling device obtained in step SS1, the p-type leg and the n-type leg described in claim 8 are cut respectively;

[0039] SS3, magnetron sputtering: magnetron sputtering of the Ni layer is performed on the p-type leg and the n-type leg obtained by cutting in step SS2, and the Ni element is sputtered on the upper and lower surfaces of the p-type leg and the n-type leg;

[0040] SS4, device assembly: The p-type legs and n-type legs obtained in step SS3 are welded to the copper-clad aluminum nitride ceramic plate through Sn-Bi solder, and then the wires are welded to complete the production of the thermoelectric cooling device.

[0041] Preferably, the specific process of the theoretical simulation in step SS1 is as follows: using Comsol software, modeling in the thermoelectric cooling module, and inputting the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 Thermoelectric properties of materials, running simulations with this p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 The maximum cooling temperature difference that can be obtained when the material is used as the p-type leg and n-type leg of a pair of cooling devices, and the sizes of the p-type leg and n-type leg corresponding to the maximum cooling temperature difference are obtained as the theoretical optimal sizes of the legs of the thermoelectric cooling device.

[0042] Preferably, in step SS1, the theoretical optimal dimensions of the p-type legs obtained by simulation are: height 3-7 mm, and cross-sectional side length 1.5 mm-2.5 mm.

[0043] Preferably, in step SS1, the theoretical optimal dimensions of the n-type legs obtained by simulation are: height 3-7 mm, and cross-sectional side length 1.5 mm-2.5 mm.

[0044] Further preferably, in step SS1, the theoretical optimal dimensions of the p-type legs obtained by simulation are: height 4-6 mm, and cross-sectional side length 1.5 mm-2.5 mm.

[0045] Further preferably, in step SS1, the theoretical optimal dimensions of the n-type legs obtained by simulation are: height 4-6 mm, and cross-sectional side length 1.5 mm-2.5 mm.

[0046] Preferably, in step SS2, the cutting rates of the p-type leg and the n-type leg during wire cutting are both 0.05-0.2 mm / min.

[0047] Further preferably, in step SS2, the cutting rates of the p-type leg and the n-type leg during wire cutting are both 0.05-0.08 mm / min.

[0048] Preferably, in step SS3, a DM300 magnetron sputtering apparatus is used, and the chamber pressure is 4.8×10 -4 ~9.8×10 - 4 Pa, the cavity temperature is room temperature.

[0049] Preferably, in step SS3, the process of magnetron sputtering Ni layer on the upper and lower surfaces of the p-type leg is: setting the DC power supply power of the instrument to 200-300W, and sputtering for 1-10 minutes; the process of magnetron sputtering Ni layer on the upper and lower surfaces of the n-type leg is: setting the DC power supply power of the instrument to 200-300W, and sputtering for 5-15 minutes.

[0050] Further preferably, in step SS3, the process of magnetron sputtering Ni layer on the upper and lower surfaces of the p-type leg is: setting the DC power supply power of the instrument to 225-275 W, and sputtering for 5-7 minutes; the process of magnetron sputtering Ni layer on the upper and lower surfaces of the n-type leg is: setting the DC power supply power of the instrument to 225-275 W, and sputtering for 7-12 minutes.

[0051] Preferably, in step SS4, the n-type leg of the welding wire is connected to the positive electrode, and the p-type leg is connected to the negative electrode.

[0052] In a fifth aspect, the present invention also provides an application of the above-mentioned thermoelectric refrigeration device in low-temperature refrigeration.

[0053] Preferably, the applications of the above-mentioned thermoelectric cooling devices in low-temperature refrigeration include: constant temperature wine cabinets, car refrigerators, etc. in the living field; portable insulin boxes, mobile medicine boxes, etc. in the medical field; temperature control of detectors and sensors in the aerospace field, etc.

[0054] Commercial p-type Bi 0.5 Sb 1.5 The carrier concentration of Te3-based thermoelectric materials is 2.84×10 19 cm -3 , PF peak is at ~250K, zT peak is at ~350K, based on its existing refrigeration capacity, it is expected to further improve the thermoelectric performance of the material below room temperature by reducing the carrier concentration of the material. 0.5 Sb 1.5 Te 3-x I xThere is a clear trend of decreasing carrier concentration under different halogen doping contents, and the maximum average zT value in the range of 180K to 300K reaches 0.81, which is significantly higher than the base sample when the doping content is 0, and the average zT value in this temperature range is increased by 22% compared with the commercial p-type bismuth telluride material. This performance improvement has achieved an increase in the maximum cooling temperature difference in thermoelectric cooling devices, providing support for the further development of thermoelectric cooling technology.

[0055] The present invention provides a p-type Bi2O3 having excellent thermoelectric performance at low temperature and used for improving the refrigeration temperature difference of thermoelectric devices. 0.5 Sb 1.5 Te3-based thermoelectric materials, thermoelectric cooling devices, and their preparation methods and applications. 0.5 Sb 1.5 Te3 is used as the matrix, and the temperature gradient growth method is used. Through the micro-doping of halogen I, the Hall carrier concentration of the material is reduced while maintaining high mobility, and the temperature corresponding to the PF peak and zT peak is moved to a lower temperature, thereby increasing the average zT of 180K to 300K, and finally realizing the p-type Bi optimized by the present invention. 0.5 Sb 1.5 Thermoelectric cooling devices made of Te3-based thermoelectric materials instead of commercial p-type thermoelectric materials have significantly improved the cooling temperature difference when the hot end temperature is 180K~300K.

[0056] According to statistics, the p-type Bi 0.5 Sb 1.5 The temperature corresponding to the zT peak value of samples with different carrier concentrations in Te3 alloy (T peak ) literature data, which basically agrees with the fact that the lower the carrier concentration, the higher the T peak The lower the trend, the T of the material optimized by the present invention peak At an excellent level.

[0057] Compared with the prior art, the present invention has the following beneficial effects:

[0058] (1) The present invention provides a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials are made by 0.5 Sb 1.5 A small amount of iodine is doped into Te3 crystals to improve their thermoelectric cooling performance below room temperature.

[0059] (2) The present invention achieves this by providing high quality oriented Bi 0.5 Sb 1.5 A small amount of iodine is doped into the Te3 crystal, which reduces the carrier concentration without changing the band structure or affecting the carrier mobility material, thereby improving the thermoelectric performance and low-temperature cooling capability.

[0060] (3) p-type Bi of the present invention 0.5 Sb 1.5 Te3-based thermoelectric materials can achieve a carrier concentration of 1.7×10 19 cm -3 , and successfully increased the PF peak to 56 μW cm -1 k -1 , and moved to a lower temperature of around 200 K, and the zT peak ~1.1 moved to around 315 K. Such optimization not only enhances the thermoelectric performance of the material below room temperature, but also expands its application potential in low temperature areas.

[0061] (4) The p-type Bi obtained by the vertical temperature gradient method 0.5 Sb 1.5 Te3-based crystalline materials are highly oriented and exhibit better thermoelectric properties.

[0062] (5) The p-type Bi optimized by the present invention 0.5 Sb 1.5 Te3-based thermoelectric materials can be used in practical thermoelectric cooling devices, achieving the maximum cooling temperature difference ΔT in the hot end temperature range from room temperature to 180K. max Compared with the performance improvement of commercial material devices, at 300K and 180K, ΔT max They are 68K and 24K respectively, and are expected to show better cooling effects through better device interfaces.

[0063] (6) The present invention is to treat p-type Bi 0.5 Sb 1.5 The optimization of Te3's low-temperature performance demonstrates the expanded cooling capabilities of thermoelectric cooling devices at low temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x X-ray diffraction pattern of the alloy;

[0065] Figure 2 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 The Hall coefficient (R H ), Hall mobility (μ H ) versus temperature;

[0066] Figure 3 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 The relationship between the Hall carrier concentration, Seebeck coefficient and Hall mobility of Te3 alloy at different temperatures;

[0067] Figure 4 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 Relationship between resistivity (ρ), Seebeck coefficient (S), power factor (PF) and temperature of Te3 alloy;

[0068] Figure 5 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 Relationship between Seebeck coefficient and power factor of Te3 alloy;

[0069] Figure 6 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 The total thermal conductivity (κ tot ), the relationship between the thermoelectric figure of merit (zT) and temperature;

[0070] Figure 7 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 Comparison of average thermoelectric figures of merit of Te3 alloys in the temperature range of 180-300K (zT ave );

[0071] Figure 8 For the optimal composition of p-type Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial n-type Bi2Te 2.79 Se0.21 The relationship between the maximum cooling temperature difference and the current of the thermoelectric cooling device made for the legs at different hot end temperatures;

[0072] Fig. 9 For the optimal composition of p-type Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial n-type Bi2Te 2.79 Se 0.21 A graph showing the relationship between the maximum cooling temperature difference and time achieved by the thermoelectric cooling device made for the legs at the optimal current at different hot end temperatures;

[0073] Fig.10 For the optimal composition of p-type Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial n-type Bi2Te 2.79 Se 0.21 Thermoelectric cooling devices made for legs and commercial p-type Bi 0.5 Sb 1.5 Te3 alloy and commercial n-type Bi2Te 2.79 Se 0.21 Comparison of the maximum cooling temperature difference of the thermoelectric cooling device made for the legs at different hot end temperatures, and the relative percentage of the maximum cooling temperature difference improvement. DETAILED DESCRIPTION

[0074] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0075] 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 commercially available.

[0076] The present invention provides a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, whose chemical formula is Bi 0.5 Sb 1.5 Te 3-x I x , where 0≤x≤0.01, x represents the molar fraction of doped I, the Bi 0.5 Sb 1.5 Te3-based thermoelectric materials are crystalline materials with high orientation.

[0077] Preparation of Bi by vertical temperature gradient growth method0.5 Sb 1.5 Te3-based thermoelectric material, the preparation process is as follows:

[0078] S1. Raw material preparation: weigh the single substances Bi, Sb, Te and binary compound TeI4 raw materials according to the stoichiometric ratio, and always add an excess of 3wt% Te as compensation for the volatilization of Te element;

[0079] S2. Loading and packaging: Put the weighed TeI4, Te, Bi, and Sb raw materials into the quartz tube in turn, and evacuate to 10 -3 ~10 -1 After Pa, vacuum packaging was performed using an oxyhydrogen flame gun;

[0080] S3, melt quenching: heating the quartz tube containing the single raw material to make the raw material react in a molten state, the process conditions of heating and heating are: heating the quartz tube from room temperature to 690-710°C at a rate of 150-200°C per hour, keeping it at the molten temperature for 6-10 hours, so that the raw material can be fully reacted in a molten state, and then quenching it in water to obtain a material ingot;

[0081] S4, gradient growth: the quartz tube containing the material ingot obtained in S3 is placed in a vertical temperature gradient furnace. During the crystal growth process, the material and the furnace body are in a relatively static state, and the temperature gradient in the crystal growth area is set to 6-10°C / cm; the temperature is set to 690-710°C, and when the ingot is fully melted, it is set to cool down to 620-680°C at a rate of 20-35K / hour; starting from 620-680°C as the initial growth temperature, it is set to cool down to 470-550°C at a rate of 1-3K / hour, and then cooled with the furnace to obtain a highly oriented crystal material.

[0082] In the following examples, the Hall coefficient (R H ), Hall mobility (μ H ), Seebeck coefficient (S), resistivity (ρ), thermal conductivity (κ), lattice thermal conductivity (κ lat ), thermoelectric figure of merit zT, effective carrier mass (m*), power factor (PF), cooling temperature difference (ΔT max ) can be measured using conventional measurement methods in the art.

[0083] Example 1

[0084] A low-carrier concentration p-type Bi with low-temperature and high thermoelectric performance 0.5 Sb 1.5 Te3-based thermoelectric material, whose chemical formula is Bi 0.5 Sb 1.5 Te 3-x I x, (0≤x≤0.01), and the preparation method thereof comprises the following steps:

[0085] (1) Press Bi 0.5 Sb 1.5 Te 3-x I x The raw materials Bi, Sb, Te and binary compound TeI4 with a stoichiometric ratio in the alloy and a purity greater than 99.99% are weighed, and a total of 30 g of the raw materials are weighed, wherein x=0, and an excess of 3 wt % Te is always added as compensation for the volatilization of the Te element; and the raw materials are vacuum-sealed in a quartz tube.

[0086] (2) The quartz tube containing the raw materials is suspended in a vertical high-temperature furnace, and the temperature is increased to 750-1000°C at a rate of 150-200°C per hour, and the temperature is kept at this temperature for 6-8 hours, and then the first ingot (i.e., the material ingot) is obtained by rapid quenching and cooling. In this step of the present embodiment, the temperature is slowly increased to 800°C at a rate of 150°C per hour, and the temperature is kept at 800°C for 6 hours.

[0087] (3) The first ingot obtained in step (2) after high-temperature melt quenching is melted and regrown: the quartz tube containing the pre-melted sample, i.e., the first ingot, is placed in a vertical temperature gradient furnace, and the temperature is set to 700°C. When the ingot is fully melted, the temperature is set to be reduced to 660°C at a rate of 20 to 35K / hour; starting from 660°C as the initial growth temperature, the temperature is set to be reduced to 510°C at a rate of 2K / hour, and then cooled with the furnace to obtain a highly oriented crystal material.

[0088] Example 2

[0089] Press Bi 0.5 Sb 1.5 Te 3-x I x The raw materials Bi, Sb, Te and binary compound TeI4 with a stoichiometric ratio of greater than 99.99% purity in the alloy are weighed, and a total of 30 g of the raw materials are weighed, wherein x=0.003, and an excess of 3 wt% Te is always added as compensation for the volatilization of the Te element; and vacuum-sealed in a quartz tube. The other steps are the same as in Example 1.

[0090] Example 3

[0091] Press Bi 0.5 Sb 1.5 Te 3-x I x The raw materials Bi, Sb, Te and the binary compound TeI4 with a stoichiometric ratio of greater than 99.99% purity in the alloy are weighed, and a total of 30 g of the raw materials are weighed, wherein x=0.0045, and an excess of 3 wt% Te is always added as compensation for the volatilization of the Te element; and vacuum-sealed in a quartz tube. The other steps are the same as in Example 1.

[0092] Example 4

[0093] Press Bi 0.5 Sb 1.5 Te 3-x I x The raw materials Bi, Sb, Te and the binary compound TeI4 with a stoichiometric ratio of greater than 99.99% purity in the alloy are weighed, and a total of 30 g of the raw materials are weighed, wherein x=0.006, and an excess of 3 wt% Te is always added as compensation for the volatilization of the Te element; and vacuum-sealed in a quartz tube. The other steps are the same as in Example 1.

[0094] Comparative Example 1

[0095] Comparative Example 1 is a commercial p-type Bi 0.5 Sb 1.5 The Te3 component does not involve the technical steps of the present invention.

[0096] Structural testing

[0097] Figure 1 Examples 1 to 4Bi of the present invention 0.5 Sb 1.5 Te 3-x I x From the XRD patterns of the alloys, it can be observed that the XRD diffraction peaks of all samples are along the (00l) direction, showing a high degree of orientation, indicating that the samples grown by the temperature gradient method in this invention are close to single crystals.

[0098] Thermoelectric performance test

[0099] Figure 2 Bi prepared in Examples 1 to 4 of the present invention 0.5 Sb 1.5 Te 3-x I x Alloy and Comparative Example 1 Commercial Bi 0.5 Sb 1.5 The Hall coefficient (R H ), Hall mobility (μ H ) and temperature. H The relationship diagram with temperature. As we all know, for the band convergence system, R changes with temperature H Usually, a peak value appears at a certain temperature. H There is a peak value near 250K, R H The temperatures corresponding to the peaks are the same, indicating that when the carrier concentration is reduced by adjusting the iodine doping concentration in the present invention, the band structure does not change significantly, which ensures that Bi 0.5 Sb 1.5 Te3-x I x The alloy still has a good band structure at low temperatures. H The relationship diagram with temperature shows that compared with Comparative Example 1, the crystals of Examples 1 to 4 have higher μ H This indicates that the highly oriented crystals obtained by the present invention have better μ H In addition, in the temperature range of 100 to 300 K, μ H ∝T -3 / 2 The law shows that the electron scattering mechanism is still dominated by phonon scattering.

[0100] Figure 3 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 Hall carrier concentration (n) of Te3 alloy at different temperatures H ) and the Seebeck coefficient (S) and the Hall mobility (μ H ) at different temperatures. H In the relationship diagram with S: the effective mass of the state density (m*) can be estimated based on the single parabolic band (SPB) model; according to the relationship between S and n at different temperatures H The Pisarenko curve shows that m* increases with increasing temperature, which is the result of the best energy band of the system near room temperature. H With μ H In the relationship diagram: H For a more detailed analysis, since the scattering intensity can be determined by the deformation potential (E def ) is used to measure the oriented crystals of Examples 1 to 4 of the present invention. The E def The average value is ~20eV, indicating that the change of carrier concentration has little effect on the scattering intensity of electrons, ensuring the feasibility of carrier concentration regulation to improve low-temperature thermoelectric performance. Due to the difference in lattice defect concentration, it can be clearly observed that as a commercial comparative example 1 polycrystalline material, its μ H Much lower than Bi 0.5 Sb 1.5 Te 3-x I x Oriented crystals.

[0101] Figure 4 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5The relationship between the resistivity (ρ), Seebeck coefficient (S), power factor (PF) and temperature of Te3 alloy. In the relationship between ρ and temperature: starting with R at 300K H The estimated carrier concentrations are shown as an example for different samples. It can be found that trace iodine doping increases the carrier concentration from 3.4×10 19 cm -3 Reduced to 1.4×10 19 cm -3 (corresponding to Example 1 reduced to Example 4); in the relationship diagram between S and temperature: Bi 0.5 Sb 1.5 Te 3-x I x The Seebeck coefficient increases with temperature before the occurrence of the dual polarization effect; since the lower hole concentration indicates that the Fermi level moves toward the conduction band, the temperature corresponding to the peak of the Seebeck coefficient for the sample with a lower carrier concentration in the figure is also lower. 2 / ρ) also shifts to lower temperatures. In the PF vs. temperature graph, for 1.7×10 19 cm -3 Low carrier concentration Bi 0.5 Sb 1.5 Te 3-x I x The alloy achieved a PF peak of ~56μW·cm at 200K -1 ·K -2 , significantly better than commercial Bi 0.5 Sb 1.5 Te3.

[0102] Figure 5 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 The relationship between the Seebeck coefficient and the power factor of Te3 alloy is the electrical quality factor (BE) analysis. BE is used to describe the role of electronic contribution to zT enhancement. BE is obtained by fitting experimental data, and some deviations from the fitting are caused by the bipolar effect. The high-quality oriented crystal Bi obtained in the present invention 0.5 Sb 1.5 Te 3-x I x BE compared to commercial Bi 0.5 Sb 1.5 Te3 is higher, ensuring Bi 0.5 Sb 1.5 Te 3-x Ix The alloy has better zT and potential low-temperature refrigeration performance.

[0103] Figure 6 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 The total thermal conductivity (κ tot ), the relationship between the thermoelectric figure of merit (zT) and temperature. Before the significant double-click effect occurs, κ tot As the temperature increases, the bipolar effect contribution increases, resulting in an increase in the total thermal conductivity. The zT value obtained in the end shows that compared with the commercial Bi 0.5 Sb 1.5 Te3,Bi 0.5 Sb 1.5 Te 3-x I x Iodine doping reduces the carrier concentration in the alloy, causing the zT peak to gradually move to a lower temperature, which is beneficial to improving low-temperature thermoelectric performance and low-temperature refrigeration capabilities.

[0104] Figure 7 Bi with different compositions 0.5 Sb 1.5 Te 3-x I x Alloy and Commercial Bi 0.5 Sb 1.5 Comparison of average thermoelectric figures of merit of Te3 alloys in the temperature range of 180-300K (zT ave ). Thanks to the optimized PF and zT in the low temperature range by reducing the carrier concentration, n H 1.7×10 19 cm -3 Bi 0.5 Sb 1.5 Te 3-x I x zT of Example 3 (x = 0.0045) in the temperature range of 180-300K ave The value is 0.81, which is 22% higher than that of commercial comparative example 1.

[0105] Example 5

[0106] A thermoelectric cooling device is prepared by the following steps:

[0107] (1) Comsol software simulation, with the optimal composition of Example 3 p-type Bi 0.5 Sb 1.5 Te 3-x Ix (x=0.0045) alloy and commercial n-type Bi2Te 2.79 Se 0.21 To match the legs, the theoretical optimal size of the legs of the thermoelectric cooling device is obtained as follows: the theoretical optimal size of the p-type legs is 5mm in height and 1.5mm to 2.5mm in cross-sectional length; the theoretical optimal size of the n-type legs is 5mm in height and 1.5mm to 2.5mm in cross-sectional length;

[0108] (2) According to the theoretical optimal size of the thermoelectric cooling device obtained in the above steps, the p-type leg and the n-type leg are cut at a cutting rate of 0.05 mm / min respectively;

[0109] (3) The p-type leg and the n-type leg obtained by cutting in step (2) were subjected to magnetron sputtering of a Ni layer using a DM300 magnetron sputtering apparatus with a chamber pressure of 9.8×10 -4 Pa, the chamber temperature is room temperature. Set the instrument DC power supply to 250W, sputter Ni element on the upper and lower surfaces of the p-type leg for 5 to 7 minutes, and sputter Ni element on the upper and lower surfaces of the n-type leg for 7 to 12 minutes;

[0110] (4) The p-type leg and the n-type leg obtained in the above steps are welded to the copper-clad aluminum nitride ceramic plate through Sn-Bi solder, and then the wires are welded and marked to connect the n-type leg to the positive electrode and the p-type leg to the negative electrode, thereby completing the production of the thermoelectric cooling device.

[0111] Figure 8 For the optimal composition embodiment 3 p-type Bi 0.5 Sb 1.5 Te 3-x I x (x=0.0045) alloy and commercial n-type Bi2Te 2.79 Se 0.21 The relationship between the maximum cooling temperature difference and the current of the thermoelectric cooling device made for the legs at different hot end temperatures. It can be seen from the figure that at different hot end temperatures (T h =300K, 280K, 240K, 200K, 180K), the refrigeration temperature difference of the refrigeration device made in the present invention is higher than the refrigeration temperature difference of the device made of commercial materials.

[0112] Fig. 9 For the optimal composition of p-type Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial n-type Bi2Te 2.79 Se 0.21The relationship between the maximum cooling temperature difference and time achieved by the thermoelectric cooling device made for the legs at the optimal current at different hot end temperatures. The raw data of the cooling temperature difference measured at the optimal current and at different hot end temperatures as a function of the power-on time further prove that the cooling temperature difference of the cooling device made in the present invention is higher than that of the device made of commercial materials.

[0113] Fig.10 For the optimal composition of p-type Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial n-type Bi2Te 2.79 Se 0.21 Thermoelectric cooling devices made for legs and commercial p-type Bi 0.5 Sb 1.5 Te3 alloy and commercial n-type Bi2Te 2.79 Se 0.21 Comparison of the maximum cooling temperature difference of the thermoelectric cooling device made for the leg at different hot end temperatures, and the relative percentage of the maximum cooling temperature difference improvement. The measured ΔT achieved by the device of the present invention and the commercial component device max are slightly lower than the theoretical prediction (without considering the interface resistance), ΔT max The improvement is achieved by (ΔT optimized -ΔT commercial ) / ΔT commercial ×100% estimation, compared with commercial modules, the device made of the optimized p-type material of the present invention achieved a cooling performance improvement of ~10% at 180K, indicating the expansion potential of bismuth telluride refrigeration devices in low-temperature refrigeration applications.

[0114] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. 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 work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, characterized in that The p-type Bi 0.5 Sb 1.5 The chemical formula of Te3-based thermoelectric materials is Bi 0.5 Sb 1.5 Te 3-x I x , where 0≤x≤0.

01.

2. A p-type Bi according to claim 1 0.5 Sb 1.5 Te3-based thermoelectric material, characterized in that 0.003≤x≤0.006。 3. A p-type Bi as claimed in any one of claims 1 to 2 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material is characterized in that: The following steps are involved: S1. Raw material preparation: weigh the single substances Bi, Sb, Te and binary compound TeI4 raw materials according to the stoichiometric ratio; S2. Loading and packaging: Put the weighed TeI4, Te, Bi, and Sb raw materials into a quartz tube in sequence, evacuate the tube, and then use a hydrogen-oxygen flame gun to perform vacuum packaging; S3, melt quenching: heating the quartz tube containing the single element raw material to make the raw material react in a molten state, and then quenching it into water to obtain a material ingot; S4, gradient growth: The quartz tube containing the material ingot obtained in S3 is placed in a vertical temperature gradient furnace, and Bi is prepared by vertical temperature gradient growth method. 0.5 Sb 1.5 Te3-based thermoelectric materials.

4. A p-type Bi according to claim 3 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material is characterized in that: In step S1, when the single substance Te is weighed, the mass of the single substance Te exceeds the mass of Bi 0.5 Sb 1.5 Te 3-x I x The stoichiometric ratio of each element in the mixture is calculated to be 2 to 4 wt% to compensate for the volatilization of Te element at high temperature.

5. A p-type Bi according to claim 3 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material is characterized in that: In step S2, the vacuum degree in the quartz tube is 10 -3 ~10 0 pa.

6. A p-type Bi according to claim 3 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material is characterized in that: In step S3, the process conditions for heating are: heating from room temperature to 690-710°C at a rate of 150-200°C per hour, and keeping at the melting temperature for 6-10 hours.

7. The p-type Bi according to claim 3 0.5 Sb 1.5 The method for preparing Te3-based thermoelectric material is characterized in that: In step S4, the process conditions of the vertical temperature gradient growth method are as follows: the temperature gradient in the crystal growth zone is 6 to 10°C / cm; the molten ingot is heated at a temperature of 690 to 710°C until fully melted, and then cooled to 620 to 680°C at a rate of 20 to 35K / hour; 620 to 680°C is used as the initial growth temperature, and the temperature is reduced to 470 to 550°C at a rate of 1 to 3K / hour, and then cooled with the furnace.

8. A thermoelectric cooling device, characterized in that: Including p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 Thermoelectric material, wherein the p-type Bi 0.5 Sb 1.5 The Te3-based thermoelectric material is the p-type Bi as claimed in any one of claims 1 to 2 0.5 Sb 1.5 Te3-based thermoelectric materials, with the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials as p-type legs of thermoelectric cooling devices, based on commercial n-type Bi2Te 2.79 Se 0.21 As the n-leg of the thermoelectric cooling device.

9. A method for preparing a thermoelectric refrigeration device according to claim 8, characterized in that: The following steps are involved: SS1. Theoretical simulation: Comsol software is used to simulate the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 The theoretical optimal size of the legs of the thermoelectric cooling device when the materials match; SS2, size cutting: according to the theoretical optimal size of the thermoelectric cooling device obtained in step SS1, the p-type leg and the n-type leg are cut respectively; SS3, magnetron sputtering: magnetron sputtering of the Ni layer is performed on the p-type leg and the n-type leg obtained by cutting in step SS2, and the Ni element is sputtered on the upper and lower surfaces of the p-type leg and the n-type leg; SS4, device assembly: The p-type legs and n-type legs obtained in step SS3 are welded to the copper-clad aluminum nitride ceramic plate through Sn-Bi solder, and then the wires are welded to complete the production of the thermoelectric cooling device.

10. Use of the thermoelectric refrigeration device according to claim 8 in low-temperature refrigeration.

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