A p-type Bi0.5Sb1.5Te3-based thermoelectric material, a thermoelectric refrigeration device, and a preparation method and application thereof

Abstract

The present application relates to a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, thermoelectric refrigeration device and preparation method and application thereof, the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, the chemical formula of the p-type Bi 0.5 Sb 1.5 Te 3‑x I x Wherein, 0≤x≤0.01.The present application takes high-purity single elements Bi, Sb, Te and binary compound TeI4 as raw materials, obtains highly oriented Bi 0.5 Sb 1.5 Te3-based thermoelectric material by gradient growth method and further prepares thermoelectric refrigeration device.Compared with prior art, the thermoelectric material of the present application obtains lower carrier concentration, moves the temperature corresponding to zT peak (-1.1) to 315K, optimizes the thermoelectric performance (average zT-0.8) in low temperature range of 180K-300K, and accordingly, improves the maximum refrigeration temperature difference of the refrigeration device.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of thermoelectric refrigeration, in particular to a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, thermoelectric refrigeration device and preparation method and application thereof. BACKGROUND

[0002] Low-temperature thermoelectric materials and refrigeration devices have wide application prospects in medical treatment, aerospace, electronic equipment and heat energy recovery fields. For example, in superconducting electronics, superconducting materials need low-temperature environment to work normally, and low-temperature thermoelectric refrigeration technology is also expected to provide the required reliable low-temperature environment for superconducting materials. Therefore, the development of high-efficiency and stable low-temperature thermoelectric materials and refrigeration devices will promote the technological innovation and industrial development in these fields. The cooling capacity of advanced thermoelectric devices is largely dependent on the performance of the material. Excellent performance requires a higher dimensionless thermoelectric figure of merit zT=S 2 Τ / ρ(κ ele +κ lat ), where S, ρ, T, κ ele , κ lat are the Seebeck coefficient, resistivity, absolute temperature, electronic thermal conductivity and lattice thermal conductivity, respectively. The maximum temperature difference ΔT c between the cold end T h and the hot end T max of the thermoelectric cooling device depends on the zT of the material, which can be approximately expressed as ΔT max =0.5zT c 2 .

[0003] Bi2Te3 material has been the best candidate among the same kind since the semiconductor was considered as the most promising material for thermoelectric cooling in the 1950s. However, in the past two decades, Bi2Te3-based thermoelectric materials have been focused on the performance improvement in the temperature range above near room temperature, and there is little research on the performance of commercial bismuth telluride below room temperature. The thermoelectric figure of merit of commercial p-type and n-type bismuth telluride materials is 1.0 (T=350K) and 0.8 (T=320K), respectively. The refrigeration temperature difference of commercial bismuth telluride devices has almost stagnated due to the long-term neglect of material performance. Therefore, there are still many scientific problems to be solved. It is worth expecting that a large number of physical foundations and experimental researches on near-room-temperature bismuth telluride-based thermoelectric semiconductors also provide rich feasibility strategies for low-temperature performance research, so as to further optimize the low-temperature thermoelectric performance of bismuth telluride-based materials and improve the refrigeration temperature difference of thermoelectric devices.

[0004] The peak of the thermoelectric figure of merit of the p-type bismuth telluride thermoelectric material in the existing commercial technology appears at 350K and decreases with the decrease of temperature below 350K, resulting in low performance below room temperature, which limits the refrigeration capacity of the existing thermoelectric refrigeration device below room temperature. At present, the refrigeration research on bismuth telluride material pays little attention to moving the peak temperature of the thermoelectric figure of merit below 350K to improve the low-temperature thermoelectric performance of the p-type bismuth telluride and the refrigeration capacity of the device. SUMMARY

[0005] The purpose of the present application is to provide a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, a thermoelectric refrigeration device and a preparation method and application thereof. The prepared thermoelectric material has excellent thermoelectric refrigeration performance at room temperature and below.

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

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

[0008] Preferably, the Bi 0.5 Sb 1.5 Te3-based thermoelectric material exhibits high orientation in the (00l) crystal plane direction.

[0009] Preferably, the Bi 0.5 Sb 1.5 Te3-based thermoelectric material is a crystal material with high orientation.

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

[0011] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I x , wherein 0

[0012] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I xIn the embodiment, 0.003≤x≤0.006, the material has lower carrier concentration in this range, and has better electrical properties and lower thermal properties at low temperature.

[0013] Further preferably, the Bi 0.5 Sb 1.5 Te 3-x I x In the embodiment, x=0.0045, the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material has more optimal carrier concentration in the temperature range of 180K-300K, so that the zT peak can be moved to lower temperature and the average zT in the temperature range of 180K-300K is the highest.

[0014] Preferably, the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material has a carrier concentration of 2.5×10 19 -1.0×10 19 cm -3 .

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

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

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

[0018] In a second aspect, the present application also provides a preparation method of the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, which comprises the following steps:

[0019] S1, raw material batching: weighing the elemental Bi, Sb, Te and binary compound TeI4 raw materials according to the stoichiometric ratio;

[0020] S2, loading and packaging: placing the weighed TeI4, Te, Bi and Sb raw materials into a quartz tube in sequence, and then vacuum packaging using a hydrogen-oxygen flame gun after vacuumizing;

[0021] S3, Melt quenching: The quartz tube containing the elemental raw material is heated to a higher temperature, so that the raw material reacts in a molten state, and then quenched in water to obtain a material ingot;

[0022] S4. Gradient Growth: A quartz tube containing the material ingot obtained in S3 is placed in a vertical temperature gradient furnace to prepare Bi using the vertical temperature gradient growth method. 0.5 Sb 1.5 Te3-based thermoelectric materials.

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

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

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

[0026] More preferably, in step S2, the vacuum degree in the quartz tube is 8 × 10⁻⁶. -1 pa.

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

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

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

[0030] Further preferably, in step S4, the process condition of the vertical temperature gradient growth method is: taking 640-660 DEG C as the initial growth temperature, setting the cooling rate to be 1.5-2.5 K / hour, and after cooling to 500-520 DEG C, cooling with the furnace.

[0031] Further preferably, in step S4, the crystal growth, i.e. the growth of the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, is carried out under the condition that the material and the furnace body are in a relatively static state.

[0032] The present application aims to improve the low-temperature performance of the p-type bismuth telluride material, and verify the improvement effect realized by the actual refrigeration device.

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

[0034] Preferably, the thermoelectric refrigeration device uses the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material as the p-type leg of the thermoelectric refrigeration device, and uses the commercial n-type Bi2Te 2.79 Se 0.21 as the n-type leg of the thermoelectric refrigeration device.

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

[0036] In a fourth aspect, the present application further provides a preparation method of the above-mentioned thermoelectric refrigeration device, comprising the following steps:

[0037] SS1, theoretical simulation: simulate the theoretical optimal size of the leg of the thermoelectric refrigeration device when the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material and the commercial n-type Bi2Te 2.79 Se 0.21 material are matched through Comsol software;

[0038] SS2, size cutting: cutting the p-type leg and the n-type leg according to the theoretically optimal size of the thermoelectric refrigeration device obtained in the step of SS1;

[0039] SS3, magnetron sputtering: magnetron sputtering of a Ni layer on the upper and lower surfaces of the p-type leg and the n-type leg obtained by cutting in the step of SS2, so as to sputter the element Ni on the upper and lower surfaces of the p-type leg and the n-type leg;

[0040] SS4, device assembly: welding the p-type leg and the n-type leg obtained in the step of SS3 to the copper-coated aluminum nitride ceramic plate by Sn-Bi solder, and then welding the wires, to complete the production of the thermoelectric refrigeration device.

[0041] Preferably, the specific process of the step of SS1 theoretical simulation is: modeling in the thermoelectric refrigeration block by Comsol software, and inputting the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material and the commercial n-type Bi2Te 2.79 Se 0.21 material, running simulation to obtain the maximum refrigeration temperature difference when the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material and the commercial n-type Bi2Te 2.79 Se 0.21 material as a pair of p-type leg and n-type leg of the refrigeration device, and taking the size of the p-type leg and the n-type leg corresponding to the maximum refrigeration temperature difference as the theoretically optimal size of the thermoelectric refrigeration device leg.

[0042] Preferably, in the step of SS1, the theoretically optimal size of the p-type leg obtained by simulation is: height 3-7 mm, cross-sectional side length 1.5-2.5 mm.

[0043] Preferably, in the step of SS1, the theoretically optimal size of the n-type leg obtained by simulation is: height 3-7 mm, cross-sectional side length 1.5-2.5 mm.

[0044] Further preferably, in the step of SS1, the theoretically optimal size of the p-type leg obtained by simulation is: height 4-6 mm, cross-sectional side length 1.5-2.5 mm.

[0045] Further preferably, in the step of SS1, the theoretically optimal size of the n-type leg obtained by simulation is: height 4-6 mm, cross-sectional side length 1.5-2.5 mm.

[0046] Preferably, in the step of SS2, the cutting rate of the p-type leg and the n-type leg during linear cutting is 0.05-0.2 mm / min.

[0047] Further preferably, in step SS2, the cutting speed of the wire cutting on the p-type leg and the n-type leg is 0.05-0.08 mm / min.

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

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

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

[0051] Preferably, in step SS4, the soldering wire is marked to connect the n-type leg to the positive electrode and the p-type leg to the negative electrode.

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

[0053] Preferably, the application of the above-mentioned thermoelectric refrigeration device in low-temperature refrigeration includes: constant-temperature wine cabinets, vehicle-mounted refrigerators, etc. in the field of life; portable insulin boxes, mobile medicine boxes, etc. in the field of medical treatment; temperature control of detectors and sensors in the field of aerospace, etc.

[0054] Commercial p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material has a carrier concentration of ~2.84*10 19 cm -3 , a PF peak at ~250 K, and a zT peak at ~350 K, and based on its existing refrigeration capacity, it is expected to further improve the thermoelectric performance below room temperature through the strategy of reducing the carrier concentration of the material. 0.5 Sb 1.5 Te 3-x I xThe study showed a significant decreasing trend in carrier concentration with varying halogen doping concentrations, achieving a maximum average zT value of 0.81 in the 180K to 300K range. This is significantly higher than the matrix sample with zero doping concentration and represents a 22% improvement in average zT value compared to commercial p-type bismuth telluride materials within this temperature range. This performance enhancement enables an increase in the maximum cooling temperature difference in thermoelectric refrigeration devices, providing support for the further development of thermoelectric refrigeration technology.

[0055] This invention provides a p-type Bi material with excellent thermoelectric performance at low temperatures, which can be used to improve the cooling temperature difference of thermoelectric devices. 0.5 Sb 1.5 Te3-based thermoelectric materials, thermoelectric refrigeration devices, their preparation methods, and applications. This material is based on Bi... 0.5 Sb 1.5 Using Te3 as a substrate and employing a temperature gradient growth method, through trace doping with halogen I, the Hall carrier concentration of the material is reduced while maintaining high mobility. This shifts the temperatures corresponding to the PF peak and zT peak to lower temperatures, thereby improving the average zT in the 180K–300K range. Ultimately, this invention achieves the optimized p-type Bip material. 0.5 Sb 1.5 Thermoelectric cooling devices made with Te3-based thermoelectric materials as a substitute for commercial p-type thermoelectric materials show a significant improvement in cooling temperature difference when the hot end temperature is between 180K and 300K.

[0056] According to statistics on optimized p-type Bi in recent years 0.5 Sb 1.5 Temperatures corresponding to the peak zT values ​​of Te3 alloy samples with different carrier concentrations (T) peak According to literature data, the lower the carrier concentration, the higher the T. peak The lower the trend, the better the T of the optimized material of this invention. peak It is at an excellent level.

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

[0058] (1) This invention provides a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials, through high-quality orientation Bi 0.5 Sb 1.5 Doping Te3 crystals with a small amount of iodine enhances their thermoelectric cooling performance below room temperature.

[0059] (2) This invention utilizes high-quality orientation Bi 0.5 Sb 1.5 Doping a small amount of iodine into Te3 crystals reduces the carrier concentration without altering the band structure or affecting the carrier mobility, thereby improving thermoelectric performance and cryogenic cooling capability.

[0060] (3) The p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, through optimization, the carrier concentration can reach 1.7 x 10 19 cm -3 , and successfully promote the PF peak to ~ 56 μW cm -1 k -1 , while moving to lower temperature near 200K, and zT peak ~ 1.1 to 315K near. Such optimization not only enhances the thermoelectric performance of the material below room temperature, but also expands its application potential in low temperature region.

[0061] (4) The p-type Bi 0.5 Sb 1.5 Te3-based crystal material obtained by vertical temperature gradient method, has high orientation, and exhibits more excellent thermoelectric performance.

[0062] (5) The optimized p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material can be used in actual thermoelectric refrigeration device, in the temperature range from room temperature to 180K, the maximum refrigeration temperature difference ΔT max relative to the performance of the commercial material device, ΔT max 68K and 24K at 300K and 180K, respectively, and is expected to exhibit better refrigeration effect through better device interface.

[0063] (6) Through the optimization of the low temperature performance of the p-type Bi 0.5 Sb 1.5 Te3, the thermoelectric refrigeration device exhibits the expanded cooling capacity at low temperature. BRIEF DESCRIPTION OF DRAWINGS

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

[0065] Figure 2 Hall coefficient (R H ), Hall mobility (μ H ) and temperature of Bi 0.5 Sb 1.5 Te 3-x I x alloys with different compositions and commercial Bi 0.5 Sb 1.5 Te3alloy;

[0066] Figure 3 Bi for different compositions 0.5 Sb 1.5 Te 3-x I x Alloys and commercial Bi 0.5 Sb 1.5 Temperature dependence of Hall carrier concentration, Seebeck coefficient and Hall mobility for Bi2Te3alloys;

[0067] Figure 4 Bi for different compositions 0.5 Sb 1.5 Te 3-x I x Alloys and commercial Bi 0.5 Sb 1.5 Temperature dependence of resistivity (p), Seebeck coefficient (S), power factor (PF) for Bi2Te3alloys;

[0068] Figure 5 Bi for different compositions 0.5 Sb 1.5 Te 3-x I x Alloys and commercial Bi 0.5 Sb 1.5 Temperature dependence of Seebeck coefficient and power factor for Bi2Te3alloys;

[0069] Figure 6 Bi for different compositions 0.5 Sb 1.5 Te 3-x I x Alloys and commercial Bi 0.5 Sb 1.5 Temperature dependence of total thermal conductivity (K tot ), thermoelectric figure of merit (zT) for Bi2Te3alloys;

[0070] Figure 7 Bi for different compositions 0.5 Sb 1.5 Te 3-x I x Alloys and commercial Bi 0.5 Sb 1.5 Comparison of average thermoelectric figure of merit (zT ave ) for Bi2Te3alloys in the temperature range 180-300 K;

[0071] Figure 8 Bi2Te3alloys with optimal composition for p-type and commercial Bi2Te 0.5 Sb 1.5 Te 3-x I x Alloys and commercial n-type Bi2Te 2.79 Se0.21 The maximum cooling temperature difference of the thermoelectric refrigeration device made of the leg at different hot end temperatures versus the current;

[0072] Figure 9 The p-type Bi 0.5 Sb 1.5 Te 3-x I x alloy and the commercial n-type Bi2Te 2.79 Se 0.21 The maximum cooling temperature difference of the thermoelectric refrigeration device made of the leg at different hot end temperatures versus the current;

[0073] Figure 10 The p-type Bi 0.5 Sb 1.5 Te 3-x I x alloy and the commercial n-type Bi2Te 2.79 Se 0.21 The maximum cooling temperature difference of the thermoelectric refrigeration device made of the leg at different hot end temperatures versus the current; 0.5 Sb 1.5 Te3 alloy and the commercial n-type Bi2Te 2.79 Se 0.21 The maximum cooling temperature difference of the thermoelectric refrigeration device made of the leg at different hot end temperatures versus the current; DETAILED DESCRIPTION

[0074] The present application will be described in detail below with reference to the drawings and specific embodiments. The embodiments are implemented on the premise of the technical solutions of the present application, and detailed implementation manners and specific operation processes are given, but the protection scope of the present application is not limited to the following embodiments.

[0075] Unless otherwise specified, the reagents, methods, instruments and equipment used in the present application 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 application provides a p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, which has a chemical formula of Bi 0.5 Sb 1.5 Te 3-x I x , wherein 0≤x≤0.01, x represents the molar fraction of I doping, and the Bi 0.5 Sb 1.5 Te3-based thermoelectric material is a crystal material with high orientation.

[0077] The Bi0.5 Sb 1.5 Te3-based thermoelectric material, the preparation process is as follows:

[0078] S1, raw material batching: the elemental Bi, Sb, Te and binary compound Tellurium I4 raw materials are weighed according to the stoichiometric ratio, and an excess of 3wt% Te is always added as compensation for the volatilization of Te element;

[0079] S2, loading and packaging: the weighed Tellurium I4, Te, Bi, Sb raw materials are sequentially placed in a quartz tube, and vacuum is extracted to 10 -3 ~10 -1 Pa, and then vacuum packaging is performed using a hydrogen-oxygen flame gun;

[0080] S3, melting and quenching: the quartz tube containing the elemental raw materials is heated and warmed, so that the raw materials react in a molten state. The process conditions for heating and warming are as follows: the quartz tube is warmed from room temperature to 690-710°C at a rate of 150-200°C per hour, and the raw materials are kept at the melting temperature for 6-10h to ensure sufficient reaction in a molten state, and then the material ingot is obtained by quenching in water;

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

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

[0083] Example 1

[0084] A low-carrier-concentration p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, which has a chemical formula of Bi 0.5 Sb 1.5 Te 3-x I x, (0≤x≤0.01), the preparation method comprising the following steps:

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

[0086] (2) the quartz tube containing the raw materials is hung in a vertical high-temperature furnace, and heated to 750-1000℃ at a rate of 150-200℃ per hour, and kept for 6-8 hours, and then rapidly quenched to obtain a first ingot (i.e. material ingot); in this embodiment, the step is selected to slowly heat to 800℃ at a rate of 150℃ per hour, and keep at 800℃ for 6 hours.

[0087] (3) melt regrowth of the first ingot obtained after high-temperature melting and quenching in step (2): 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℃, and when the ingot is fully melted, the temperature is set to decrease to 660℃ at a rate of 20-35K / hour; starting from 660℃ as the initial growth temperature, the temperature is set to decrease to 510℃ at a rate of 2K / hour, and then cooled with the furnace, to obtain a highly oriented crystal material.

[0088] Example 2

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

[0090] Example 3

[0091] according to Bi 0.5 Sb 1.5 Te 3-x I x alloy stoichiometric ratio of raw materials Bi, Sb, Te and binary compound TeI4 with a purity greater than 99.99%, a total of 30g of the raw materials are weighed, wherein x=0.0045, and an excess of 3wt% Te is always added as compensation for the volatilization of Te element; and vacuum packaging in a quartz tube. 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 stoichiometric ratio of raw materials Bi, Sb, Te, and the binary compound TeI4 with a purity greater than 99.99% was weighed in the alloy, totaling 30g, where x = 0.006, and an excess of 3wt% Te was always added as compensation for Te volatilization; and the alloy was vacuum-sealed in a quartz tube. Other steps were 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 is not related to the technical steps of this 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 The XRD patterns of the alloy show that the XRD diffraction peaks of all samples are along the (00l) direction, exhibiting 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 testing

[0099] Figure 2 Bi prepared in Examples 1-4 of this 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) of Te3 alloy H Hall mobility (μ) H A graph showing the relationship between R and temperature. H The relationship between R and temperature is well known; for bandgap convergent systems, R varies with temperature. H A peak value typically appears at a certain temperature. Examples 1-4 and Comparative Example 1 in the figure all show R... H A peak is observed near 250K, R H The fact that the peak values ​​correspond to the same temperature indicates that when the carrier concentration is reduced by adjusting the iodine doping concentration in this invention, the band structure does not change significantly. This ensures that Bi... 0.5 Sb 1.5 Te3-x I x The alloy still has a good band structure at low temperature. For μ H The crystal has a higher μ H , which indicates that the highly oriented crystal obtained by the present application has a more optimal μ H . In addition, in the temperature range of 100-300 K, μ H ∝T -3 / 2 , which indicates that the scattering mechanism of the electrons is still dominated by phonon scattering.

[0100] Figure 3 Bi 0.5 Sb 1.5 Te 3-x I x alloy and commercial Bi 0.5 Sb 1.5 Te3alloy. The relationship diagrams of Hall carrier concentration (n H ) and Zabek coefficient (S) and Hall mobility (μ H ) at different temperatures. In the n H -S relationship diagram at different temperatures: the effective mass of the state density (m*) can be estimated based on the single parabolic band (SPB) model; according to the Pisarenko curve of S and n H at different temperatures, m* increases with the increase of temperature, which is the result of the best band of the system near room temperature. In the n H -μ H relationship diagram at different temperatures: a more detailed analysis of μ H is presented, since the scattering intensity can be measured by the deformation potential (E def ), for the oriented crystals of examples 1-4 of the present application, E def at the same temperature and at different temperatures are all about 20 eV, which indicates that the change of carrier concentration has little effect on the scattering intensity of the electrons, which guarantees the feasibility of the carrier concentration regulation to improve the thermoelectric performance at low temperature. Due to the difference in the lattice defect concentration, it can be clearly observed that the μ H of the commercial polycrystalline material of comparative example 1 is much lower than that of the Bi 0.5 Sb 1.5 Te 3-x I x oriented crystal.

[0101] Figure 4 Bi 0.5 Sb 1.5 Te 3-x I x alloy and commercial Bi 0.5 Sb 1.5The resistivity (ρ), Seebeck coefficient (S), and power factor (PF) of Te3 alloy are plotted against temperature. In the ρ vs. temperature plot: starting with R through 300K... H The estimated carrier concentrations, used as examples for different samples, show that trace amounts of iodine doping can increase the carrier concentration from 3.4 × 10⁻⁶ to 3.4 × 10⁻⁶. 19 cm -3 Reduced to 1.4 × 10 19 cm -3 (corresponding to Example 1 to Example 4 respectively); In the relationship graph of S versus temperature: Bi 0.5 Sb 1.5 Te 3-x I x The Seebeck coefficient increases with increasing temperature before the bipolarization effect occurs; since lower hole concentrations indicate that the Fermi level shifts to the conduction band, samples with lower carrier concentrations in the figure correspond to lower temperatures at which the Seebeck coefficient peaks. Therefore, the power factor (PF = S) corresponds to... 2 The peak value of / 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 peak power (PF) of ~56 μw·cm at 200 K. -1 ·K -2 It is significantly superior to commercial Bi 0.5 Sb 1.5 Te3.

[0102] Figure 5 Bi with different components 0.5 Sb 1.5 Te 3-x I x Alloys and Commercial Bi 0.5 Sb 1.5 The relationship between the Seebeck coefficient and power factor of Te3 alloy, i.e., electrical quality factor (BE) analysis, is presented. BE describes the effect of electronic contributions on zT enhancement. BE is obtained by fitting experimental data, and some deviations from the fit are due to bipolar effects. The high-quality oriented crystalline Bi3 alloy obtained in this invention... 0.5 Sb 1.5 Te 3-x I x BE compared to commercial BE 0.5 Sb 1.5 Te3 is higher, ensuring Bi 0.5 Sb 1.5 Te 3-x Ix Alloy with better zT and potential low temperature refrigeration performance.

[0103] Figure 6 Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial Bi 0.5 Sb 1.5 Total thermal conductivity (κ tot ) of Bi tot Sb 0.5 Te3alloy as a function of temperature. κ 1.5 decreases with increasing temperature, while the bipolar effect contribution increases with increasing temperature, leading to an increase of total thermal conductivity with increasing temperature. The resulting zT values show that Bi 0.5 Sb 1.5 Te 3-x I x Alloy has a gradually shifted zT peak to lower temperature due to the reduced carrier concentration by iodine doping, which is beneficial for improving low temperature thermoelectric performance and low temperature refrigeration capability.

[0104] Figure 7 Bi 0.5 Sb 1.5 Te 3-x I x Alloy and commercial Bi 0.5 Sb 1.5 Average thermoelectric figure of merit (zT ave ) of Bi H Sb 19 Te3alloy in the temperature range of 180-300 K. Benefiting from the optimized PF and zT in the low temperature range by reducing the carrier concentration, n -3 Bi 0.5 Sb 1.5 Te 3-x I x (x = 0.0045) has a zT ave of 0.81, which is 22% higher than that of commercial Reference Example 1.

[0105] Example 5

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

[0107] (1) Simulation by Comsol software to obtain the 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 refrigeration device is obtained: the theoretical optimal size of the p-type leg is 5mm in height and 1.5mm-2.5mm in cross-section side length; the theoretical optimal size of the n-type leg is 5mm in height and 1.5mm-2.5mm in cross-section side length.

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

[0109] (3) The p-type leg and the n-type leg obtained by cutting in step (2) are subjected to magnetron sputtering of a Ni layer, a DM300 magnetron sputtering instrument is used, the cavity pressure is set to 9.8x10 -4 Pa, and the cavity temperature is room temperature. The direct current power of the instrument is set to 250W, the p-type leg is subjected to Ni element sputtering for 5-7min on the upper and lower surfaces respectively, and the n-type leg is subjected to Ni element sputtering for 7-12min on the upper and lower surfaces respectively;

[0110] (4) The p-type leg and the n-type leg obtained in the above step are welded with a copper-coated aluminum nitride ceramic plate through Sn-Bi solder, then the wires are welded and marked, the n-type leg is connected to the positive electrode, and the p-type leg is connected to the negative electrode, and the production of the thermoelectric refrigeration device is completed.

[0111] Figure 8 To make the 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 diagram between the maximum refrigeration temperature difference and the current of the thermoelectric refrigeration device made of the legs at different hot end temperatures. As can be seen from the diagram, under different hot end temperatures (T h =300K, 280K, 240K, 200K, 180K), the refrigeration temperature difference of the refrigeration device made in the application is higher than that of the device made of commercial materials.

[0112] Figure 9 To make the p-type Bi 0.5 Sb 1.5 Te 3-x I x alloy and commercial n-type Bi2Te 2.79 Se 0.21The plot of the maximum temperature difference (ΔT) of the thermoelectric cooling device made with the leg versus time at different hot side temperatures with the optimal current. The raw data of the temperature difference versus time at different hot side temperatures with the optimal current further prove that the temperature difference of the cooling device made in the present application is higher than that of the device made with the commercial materials.

[0113] Figure 10 The maximum temperature difference (ΔT) of the thermoelectric cooling device made with the leg versus time at different hot side temperatures with the optimal current. The raw data of the temperature difference versus time at different hot side temperatures with the optimal current further prove that the temperature difference of the cooling device made in the present application is higher than that of the device made with the commercial materials. 0.5 Sb 1.5 Te 3-x I x alloy and the commercial n-type Bi2Te 2.79 Se 0.21 The maximum temperature difference (ΔT) of the thermoelectric cooling device made with the leg versus time at different hot side temperatures with the optimal current. The raw data of the temperature difference versus time at different hot side temperatures with the optimal current further prove that the temperature difference of the cooling device made in the present application is higher than that of the device made with the commercial materials. 0.5 Sb 1.5 Te3alloy and the commercial n-type Bi2Te 2.79 Se 0.21 The maximum temperature difference (ΔT) of the thermoelectric cooling device made with the leg versus time at different hot side temperatures with the optimal current. The raw data of the temperature difference versus time at different hot side temperatures with the optimal current further prove that the temperature difference of the cooling device made in the present application is higher than that of the device made with the commercial materials. max all are slightly lower than the theoretical predicted values (without considering the interface resistance), the improvement of ΔT max is estimated by (ΔT optimized - ΔT commercial ) / ΔT commercial x 100%. Compared with the commercial module, the device made with the optimized p-type material in the present application has achieved a ~10% improvement in cooling performance at 180 K, indicating the potential of the bismuth telluride cooling device in low-temperature cooling applications.

[0114] The above description of the embodiments is to assist the person of ordinary skill in the art to understand and use the present application. 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 labor. Therefore, the present application is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art within the scope of the present application without departing from the scope of the present application should be within the protection scope of the present application.

Claims

1. A p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material characterized by, The p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material has a chemical formula of Bi 0.5 Sb 1.5 Te 3-x I x , wherein 0 x ≤0.01; the Bi 0.5 Sb 1.5 Te3-based thermoelectric material shows high orientation in the (00l) crystal face direction.

2. A p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material characterized by, 0.003≤ x ≤0.006。 3. A p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material, characterized by, Comprising the following steps: S1, raw material batching: taking the elemental Bi, Sb, Te and binary compound Tellurium Iodide raw materials according to stoichiometric ratio; S2, loading and packaging: placing the weighed Tellurium Iodide, Tellurium, Bismuth and Antimony raw materials into a quartz tube in sequence, vacuumizing and then vacuum packaging using a hydrogen-oxygen flame gun; S3, melting and quenching: heating and warming the quartz tube containing the elemental raw materials to make the raw materials react in a molten state, and then quenching 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 a Bi 0.5 Sb 1.5 Te3-based thermoelectric material.

4. A p-type Bi 0.5 Sb 1.5 A method for producing a thermoelectric material of the system Bi In the step S1, when the elemental Te is weighed, the mass of the elemental Te is 2 to 4 wt% more than the mass calculated from the stoichiometric ratio of each element in Bi 0.5 Sb 1.5 Te 3-x I x to compensate for the volatilization of the Te element at high temperatures.

5. A p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric material production method characterized by, In step S2, the vacuum degree in the quartz tube is 10 -3 ~10 0 pa.

6. A p-type Bi 0.5 Sb 1.5 A method for producing a thermoelectric material of the formula Bi In step S3, the process conditions for heating and warming are: warming from room temperature to 690-710℃ at a rate of 150-200℃ per hour, and maintaining the molten temperature for 6-10h.

7. A p-type Bi 0.5 Sb 1.5 A method for producing a thermoelectric material of the system Bi In step S4, the process conditions for the vertical temperature gradient growth method are: the temperature gradient of the crystal growth area is 6-10℃ / cm; heating the molten ingot to 690-710℃ until it is fully melted, and then cooling at a rate of 20-35K / hour to 620-680℃; using 620-680℃ as the initial growth temperature, and then cooling at a rate of 1-3K / hour to 470-550℃, and then cooling with the furnace.

8. A thermoelectric refrigeration device, characterized by, comprising p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 thermoelectric materials, wherein the p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials are p-type Bi 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 a thermoelectric refrigeration device, with commercial n-type Bi2Te 2.79 Se 0.21 as n-type legs of a thermoelectric refrigeration device.

9. A method of producing a thermoelectric refrigeration device as claimed in claim 8, characterized in that, Comprising the following steps: SS1, Theoretical modeling: The p-type Bi 0.5 Sb 1.5 Te3-based thermoelectric materials and commercial n-type Bi2Te 2.79 Se 0.21 Theoretical optimum dimensions of a thermoelectric cooler leg when the materials are matched. SS2, size cutting: cutting the p-type leg and the n-type leg respectively according to the theoretically optimal size of the thermoelectric refrigeration device obtained in step SS1; SS3, magnetron sputtering: magnetron sputtering of a Ni layer on the p-type leg and the n-type leg cut in step SS2, to sputter the Ni element on the upper and lower surfaces of the p-type leg and the n-type leg; SS4, device assembly: welding the p-type leg and the n-type leg obtained in step SS3 to the copper-coated aluminum nitride ceramic plate through Sn-Bi solder, and then welding the wires to complete the production of the thermoelectric refrigeration device.

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

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