Preparation method of large-size silver-antimony-tellurium-based thermoelectric semiconductor single crystal

Abstract

The invention relates to the technical field of crystal growth, and discloses a preparation method of a large-size silver-antimony-tellurium-based thermoelectric semiconductor single crystal. The preparation method comprises the following steps: 1) mixing and melting raw material elementary substances, and cooling to obtain a silver-antimony-tellurium-based polycrystal; (2) putting the sealed container filled with the silver-antimony-tellurium-based polycrystals into a vertical growth furnace, and sequentially passing through a melting region, a crystal growth region and an annealing region during descending; wherein the temperature of the melting zone is 950-1100 DEG C; the temperature of a crystal growth area is 650-900 DEG C, the temperature is gradually reduced from top to bottom by 20-40 DEG C / cm, and the single crystal growth speed is 1-3 mm / h; the temperature of an annealing area is 300-500 DEG C; according to the specific method disclosed by the invention, the large-size silver-antimony-tellurium-based thermoelectric semiconductor single crystal material with target thermoelectric performance (the thermoelectric figure of merit zT value in a 450-600K interval is 0.6-0.8) can be successfully prepared, and the requirements of specific use scenes can be met.

Description

Technical Field

[0001] The invention relates to the technical field of crystal growth, and in particular to a method for preparing a large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystal. Background Art

[0002] As a green and environmentally friendly technology that can directly realize the mutual conversion of thermal energy and electrical energy, thermoelectric conversion technology has gradually attracted people's attention and been applied in many fields in recent years.

[0003] The energy conversion efficiency of thermoelectric conversion technology is measured by the thermoelectric performance of the material. People usually use the thermoelectric figure of merit zT to characterize the thermoelectric performance of the material. The zT value of the thermoelectric material can be expressed as zT = S2 σ T / K, where S is the Seebeck coefficient of the material, σ is the electrical conductivity of the material, T is the absolute temperature, and K is the total thermal conductivity of the material. Ag-based ternary chalcogenides are an important component of medium-temperature thermoelectric materials, among which AgSbTe 2 As an intrinsic high-performance thermoelectric material, it has broad application prospects.

[0004] In the prior art, silver antimony tellurium-based thermoelectric semiconductor crystal materials are usually prepared by hot pressing. The disadvantage of this method is that only polycrystalline crystals can be obtained but single crystals cannot be formed. In addition, it is also difficult to prepare larger-sized silver antimony tellurium-based thermoelectric semiconductor crystal materials with the prior art. Therefore, it is urgent to develop a new process that can successfully produce large-sized silver antimony tellurium-based thermoelectric semiconductor single crystals with excellent thermoelectric performance.

[0005] In addition, since different usage scenarios have different ambient temperatures, and the thermoelectric properties of thermoelectric semiconductor crystal materials will change with temperature. If the thermoelectric properties of thermoelectric semiconductor crystal materials at a specific ambient temperature cannot meet the requirements of the usage scenario, it will seriously affect its use effect. Therefore, in order to meet the needs of different usage scenarios, thermoelectric semiconductor crystal materials with different thermoelectric properties need to be customized according to different needs. Summary of the invention

[0006] The purpose of the present invention is to obtain a large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystal material having the required thermoelectric performance (thermoelectric figure of merit zT value 0.6-0.8) in the specific temperature range of 450-600K to meet the needs of specific usage scenarios. To this end, the present invention provides a method for preparing a large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystal. According to the specific method of the present invention, a large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystal material that meets the above requirements can be successfully prepared, which can meet the above-mentioned specific usage scenario requirements.

[0007] The specific technical solution of the present invention is: a method for preparing a large-size silver antimony tellurium-based thermoelectric semiconductor single crystal, which specifically includes the following steps: 1) Mix and melt each raw material, and then cool to obtain silver antimony tellurium based polycrystal.

[0008] In step 1), according to the chemical composition of the target silver antimony tellurium-based polycrystal, the single elements are evenly mixed, melted and cooled to obtain silver antimony tellurium-based polycrystal material, which is prepared for the subsequent preparation of single crystals.

[0009] 2) placing a sealed container containing silver antimony tellurium-based polycrystals in a vertical growth furnace, controlling the container to descend, and passing through a melting zone, a crystal growth zone and an annealing zone in sequence; wherein, the temperature of the melting zone is 950-1100°C; the temperature of the crystal growth zone is 650-900°C, and the temperature decreases from top to bottom by 20-40°C / cm, and the single crystal growth rate is controlled to be 1-3mm / h by controlling the descending speed; the temperature of the annealing zone is 300-500°C; and finally, a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal with a thermoelectric figure of merit zT value of 0.6-0.8 in the range of 450-600K, a diameter of 10-80mm, and a length of 10-100mm is obtained.

[0010] In step 2), the inner cavity of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone with decreasing temperatures from top to bottom. The sealed container containing the silver antimony tellurium-based polycrystal passes through the above three temperature zones in turn during the descent process. Specifically, the silver antimony tellurium-based polycrystal becomes a molten state in the high-temperature melting zone. In the process of descending through the crystal growth zone, the temperature decreases. When passing through a certain temperature point, the temperature of the silver antimony tellurium-based polycrystal is supercooled and crystallizes from the molten state. In the continuous descent process, the speed is controlled to make the silver antimony tellurium-based single crystal grow slowly at a specific speed until the single crystal growth ends; when descending to the annealing zone with a lower temperature, the crystal that has finished growing is subjected to low-temperature annealing to obtain a silver antimony tellurium-based thermoelectric semiconductor single crystal.

[0011] As mentioned above, the purpose of the present invention is to obtain a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal material having the required thermoelectric performance (thermoelectric figure of merit zT value 0.6-0.8) in the specific temperature range of 450-600K. In order to obtain a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal material that meets the requirements of the above-mentioned specific usage scenarios, the present invention strictly limits the process conditions. The present invention finds that in addition to the temperature settings of the three temperature intervals, the temperature decrease parameters of the crystal growth zone temperature and the single crystal growth rate will also directly affect the thermoelectric properties of the final single crystal material. Specifically: (a) Regarding the temperature decreasing parameter of the crystal growth zone temperature: The present invention finds that setting the temperature decreasing parameter within the range of 20-40°C / cm is not only more conducive to the growth of single crystals, but also enables its thermoelectric performance to meet the requirements of the present invention. If the temperature decreasing gradient is too large, firstly, it will cause the internal stress of the crystal to increase, resulting in deformation and cracking of the crystal, thereby affecting the quality and integrity of the crystal. Secondly, too large a temperature decreasing gradient will also lead to unstable crystal growth, increasing internal defects and bubbles. On the contrary, if the temperature decreasing gradient is too small, firstly, the crystal is in a high temperature environment for a long time, which is easy to cause the crystal to dissolve, reduce the crystal quality, and make it impossible to obtain the specific thermoelectric performance expected by the present invention. Secondly, too small a temperature decreasing gradient will also cause uneven crystal growth, forming a large amount of polycrystalline or amorphous, affecting the purity and performance of the crystal.

[0012] (b) Regarding the crystal growth rate: The present invention has found that, similar to the temperature decrease parameter of the crystal growth zone temperature, setting the crystal growth rate within the range of 1-3 mm / h is not only more conducive to the growth of single crystals, but also enables its thermoelectric performance to meet the requirements of the present invention. If the growth rate is too fast, the number of internal defects in the crystal increases, and the crystal growth area becomes narrower, affecting the growth quality of the crystal; on the contrary, if the growth rate is slow, the crystallization rate is slow, and the grain size becomes smaller, resulting in its thermoelectric performance failing to meet the requirements.

[0013] Preferably, in step 2), the composition of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is (AgSbTe 2 ) x (PbTe) 1-x or (AgSbTe 2 ) x (GeTe) 1-x ; The value range of x is 0-0.9 (further preferably 0.8-0.85).

[0014] (AgSbTe 2 ) x (PbTe) 1-x or (AgSbTe 2 ) x (GeTe) 1-x Compared with AgSbTe 2 In terms of PbTe, 1-x or (GeTe) 1-x The performance of the crystal can be made to better meet the requirements of the present invention.

[0015] Preferably, in step 2), the diameter of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is 15-40 mm.

[0016] Preferably, step 1) specifically comprises: placing each raw material element into a container and vacuum-sealing it, placing it into a vertical melting furnace or a rocking furnace to melt it, and obtaining silver antimony tellurium-based polycrystals after cooling.

[0017] Preferably, in step 1), the vacuum degree of the vacuum seal is 10 -2 -10 -3 pa; the melting temperature is 1050-1200°C, and the heating rate is 2-10°C / min.

[0018] Preferably, in step 1), the rocking rate of the rocking furnace is 10-30 r / min, and the rocking time is 0.5-3 h.

[0019] Preferably, the container is a crucible, more preferably a quartz crucible, the bottom of which is conical with a taper of 18-54°.

[0020] Preferably, in step 2), a seed crystal is used or not used during the single crystal growth process. If a seed crystal is needed, it is pre-filled in the quartz crucible of step 2). The seed crystal is a silver antimony tellurium-based thermoelectric semiconductor single crystal material.

[0021] Compared with the prior art, the beneficial effects of the present invention are: The present invention provides a method for preparing large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystals. According to the specific method of the present invention, a large-sized silver-antimony-tellurium-based thermoelectric semiconductor single crystal material with target thermoelectric performance (thermoelectric figure of merit zT value = 0.6-0.8 in the range of 450-600K) can be successfully prepared, which can meet the requirements of the above-mentioned specific usage scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the X-ray diffraction pattern of the silver antimony tellurium based thermoelectric semiconductor crystal of Example 1 of the present invention.

[0023] Figure 2 This is a surface scanning spectrum of element distribution of the silver antimony tellurium based thermoelectric semiconductor crystal of Example 1 of the present invention. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the embodiments.

[0025] Overall embodiment First, a method for preparing a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal specifically comprises the following steps: 1) Mix and melt each raw material, and then cool to obtain silver antimony tellurium based polycrystal.

[0026] In some preferred implementation cases, step 1) specifically includes: placing each raw material element into a container and vacuum-sealing it, placing it into a vertical melting furnace or a rocking furnace to melt it, and obtaining silver antimony tellurium-based polycrystals after cooling.

[0027] In some more preferred implementation cases, in step 1), the vacuum degree of the vacuum seal is 10 -2 -10 -3 pa; the melting temperature is 1050-1200°C, and the heating rate is 2-10°C / min.

[0028] In some more preferred implementation cases, in step 1), the rocking rate of the rocking furnace is 10-30 r / min, and the rocking time is 0.5-3 h.

[0029] In some more preferred implementation cases, the container is a crucible, most preferably a quartz crucible, the bottom of which is conical with a taper of 18-54°.

[0030] 2) placing a sealed container containing silver antimony tellurium-based polycrystals in a vertical growth furnace, controlling the container to descend, and passing through a melting zone, a crystal growth zone and an annealing zone in sequence; wherein, the temperature of the melting zone is 950-1100°C; the temperature of the crystal growth zone is 650-900°C, and the temperature decreases by 20-40°C / cm from top to bottom, and the single crystal growth rate is controlled to be 1-3mm / h by controlling the descending speed; the temperature of the annealing zone is 300-500°C; and finally, a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal with a diameter of 10-80mm and a length of 10-100mm is obtained.

[0031] In some preferred implementation cases, in step 2), the residence time of the silver antimony tellurium-based polycrystal in the melting zone is 8-15 hours; and the residence time of the annealing zone is 8-20 hours.

[0032] In some preferred implementation cases, in step 2), a seed crystal is used or not used during the single crystal growth process. If a seed crystal is required, it is pre-filled in the quartz crucible of step 2). In some more preferred implementation cases, the seed crystal is a silver antimony tellurium-based thermoelectric semiconductor single crystal material.

[0033] In some preferred implementation cases, in step 2), the composition of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal finally obtained is (AgSbTe 2 ) x (PbTe) 1-x or (AgSbTe 2 ) x (GeTe) 1-x ; wherein the value range of x is x=0-0.9. In some more preferred implementation cases, the composition of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal finally obtained is AgSbTe2 、(AgSbTe 2 ) x (PbTe) 1-x or (AgSbTe 2 ) x (GeTe) 1- ; Wherein, the value range of x is x=0.8-0.85.

[0034] In some preferred implementation cases, in step 2), the diameter of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is 15-40 mm.

[0035] Specific Examples and Comparative Examples (I) Effects of Different Temperature Decrease Parameters in the Crystal Growth Zone Examples 1-3 and Comparative Examples 1-2 A method for preparing a large-size silver antimony tellurium-based thermoelectric semiconductor single crystal, which specifically comprises the following steps: 1) AgSbTe 2 Preparation of polycrystals: According to AgSbTe 2 The raw materials (Ag, Sb, Te) were placed in a quartz crucible (30 cm in length, 17 mm in inner diameter, conical bottom, 36° in taper) and mixed evenly. The crucible was then sealed with vacuum until the vacuum degree reached 10 -2 Then the quartz crucible is placed in a swing furnace, and the swing furnace is controlled to heat up to 1100°C at a heating rate of 6°C / min. During this period, the swing rate of the swing furnace is 20r / min, and the swing time is 2h, until all the raw materials are fully melted and mixed, and then cooled to obtain AgSbTe 2 Polycrystalline.

[0036] 2) AgSbTe 2 Preparation of single crystal: Will be equipped with AgSbTe 2A polycrystalline quartz crucible is placed in a vertical growth furnace. The interior of the furnace chamber of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone from top to bottom. The temperature of the melting zone is set to 1050°C; the temperature range of the crystal growth zone is set to 650-900°C, and the temperature of the crystal growth zone is set to decrease from top to bottom by 10-50°C / cm (the parameters of Comparative Example 1, Examples 1-3 and Comparative Example 2 are specifically shown in Table 1); the temperature of the annealing zone is set to 400°C. After the temperature in the vertical growth furnace reaches the preset target, the quartz crucible is controlled by the lifter to begin to descend from the melting zone position at the top of the vertical growth furnace cavity, and passes through the melting zone, crystal growth zone and annealing zone in turn during the descent. The residence time of the quartz crucible in the melting zone is 12h; the single crystal growth rate of the material in the crystal growth zone is 1.5mm / h by controlling the descent speed; the residence time of the quartz crucible in the annealing zone is 14h; after the annealing treatment is completed, it is cooled to room temperature to obtain a large-size AgSbTe 2 Thermoelectric semiconductor single crystal, the chemical composition of this material is AgSbTe 2 , single crystal, diameter 17mm, length 30mm. Among them, Figure 1 is the X-ray diffraction pattern of the silver antimony tellurium based thermoelectric semiconductor crystal of Example 1 of the present invention; Figure 2 This is a surface scanning spectrum of element distribution of the silver antimony tellurium based thermoelectric semiconductor crystal of Example 1 of the present invention.

[0037] Comparative Example 1, Examples 1-3 and Comparative Example 2 obtained large-size AgSbTe 2 The thermoelectric properties of thermoelectric semiconductor single crystals were tested, and the results are shown in the following table: Table 1 From the comparison of the data in the above table, we can see that: From Comparative Example 1, Examples 1-3 to Comparative Example 2, the temperature decrease parameter in the crystal growth zone gradually increased. It was found that the large-sized AgSbTe obtained in Examples 1-3 2 The thermoelectric semiconductor single crystal has a thermoelectric optimum value of 0.6-0.8 in the temperature range of 450K-600K. The thermoelectric optimum value of Example 2 is more stable at different temperatures in the range of 450K-600K, so it is best to set the temperature decrease parameter to 30°C / cm.

[0038] In Comparative Example 1, since the temperature decrease parameter in the crystal growth zone is too low, the thermoelectric value of the final crystal cannot meet the requirements (the thermoelectric value parallel to the single crystal axis is lower than 0.6 at 450K and 600K). The reason may be that the crystal growth is uneven, forming a large amount of polycrystalline or amorphous, which ultimately affects the thermoelectric properties of the crystal.

[0039] In Comparative Example 2, since the temperature decrease parameter is too high, the internal stress of the crystal increases and a large number of cracks appear in the crystal, making it impossible to obtain a complete single crystal material. Therefore, the thermoelectric performance test was not carried out.

[0040] (II) Influence of different crystal growth rates Examples 4-6 and Comparative Examples 3-4 A method for preparing a large-size silver antimony tellurium-based thermoelectric semiconductor single crystal, which specifically comprises the following steps: 1) AgSbTe 2 Preparation of polycrystals: According to AgSbTe 2 The raw materials (Ag, Sb, Te) were placed in a quartz crucible (length 30 cm, inner diameter 17 mm, conical bottom, taper 36°) and mixed evenly, and then vacuumed and sealed until the vacuum degree reached 10 -2 Then the quartz crucible is placed in a swing furnace, and the swing furnace is controlled to heat up to 1100°C at a heating rate of 6°C / min. During this period, the swing rate of the swing furnace is 20r / min, and the swing time is 2h, until all the raw materials are fully melted and mixed, and then cooled to obtain AgSbTe 2 Polycrystalline.

[0041] 2) AgSbTe 2 Preparation of single crystal: Will be equipped with AgSbTe 2 A polycrystalline quartz crucible is placed in a vertical growth furnace. The interior of the furnace chamber of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone from top to bottom. The temperature of the melting zone is set to 4050°C; the temperature range of the crystal growth zone is set to 650-900°C, and the temperature of the crystal growth zone is set to decrease by 30°C / cm from top to bottom; the temperature of the annealing zone is set to 400°C. After the temperature in the vertical growth furnace reaches the preset target, the quartz crucible is controlled by the lifter to start descending from the melting zone position at the top of the vertical growth furnace cavity, and passes through the melting zone, crystal growth zone and annealing zone in sequence during the descent. The residence time of the quartz crucible in the melting zone is 12h; by controlling the descent speed, the single crystal growth rate of the material in the crystal growth zone is 0.5-3mm / h (the parameters of Comparative Example 3, Examples 4-6 and Comparative Example 4 are specifically shown in Table 2); the residence time of the quartz crucible in the annealing zone is 8-20h; after the annealing treatment is completed, it is cooled to room temperature to obtain a large-size AgSbTe 2 Thermoelectric semiconductor single crystal, the chemical composition of this material is AgSbTe 2 , single crystal, diameter 17mm, length 30mm.

[0042] Comparative Example 3, Examples 4-6 and Comparative Example 4 obtained large-size AgSbTe2 The thermoelectric properties of thermoelectric semiconductor single crystals were tested, and the results are shown in the following table: Table 2 From the comparison of the data in the above table, we can see that: From Comparative Example 3, Examples 4-6 to Comparative Example 4, the crystal growth rate gradually increased. It was found that the large-sized AgSbTe obtained in Examples 4-6 2 The thermoelectric semiconductor single crystal has a thermoelectric optimum value of 0.6-0.8 in the temperature range of 450K-600K. The thermoelectric optimum value of Example 5 is more stable at different temperatures in the range of 450K-600K, so it is best to set the temperature decrease parameter to 30°C / cm.

[0043] In Comparative Example 3, due to the slow crystal growth rate, the final thermoelectric performance cannot meet the requirements (the thermoelectric value parallel to the single crystal axis at 450K, 550K and 600K is lower than 0.6). Analysis shows that the reason may be that the crystal growth rate is too slow, the grain size becomes smaller, and finally affects the thermoelectric performance of the crystal.

[0044] In Comparative Example 4, due to the excessively fast crystal growth rate, the final thermoelectric performance cannot meet the requirements (the thermoelectric value parallel to the single crystal axis is less than 0.6 at 550K and 600K). Analysis shows that the reason may be that the excessively fast crystal growth rate leads to an increase in internal defects in the crystal, and the narrowing of the crystal growth area affects the growth quality of the crystal.

[0045] Example 7 (AgSbTe 2 ) 0.8 (PbTe) 0.2 ) A method for preparing a large-sized AgSbTe-based thermoelectric semiconductor single crystal, which specifically comprises the following steps: 1)(AgSbTe 2 ) 0.8 (PbTe) 0.2 Preparation of polycrystals: According to (AgSbTe 2 ) 0.8 (PbTe) 0.2 The raw materials (Ag, Sb, Te, Pb) were placed in a quartz crucible (30 cm in length, 20 mm in diameter, conical bottom, 36° in taper) and mixed evenly. The crucible was evacuated and sealed until the vacuum degree reached 10 -3Then the quartz crucible was placed in a swing furnace, and the swing furnace was controlled to heat up to 1150°C at a heating rate of 8°C / min. During this period, the swing rate of the swing furnace was 15r / min, and the swing time was 2.5h, until the raw materials were fully melted and mixed, and then cooled to obtain (AgSbTe 2 ) 0.8 (PbTe) 0.2 Polycrystalline.

[0046] 2)(AgSbTe 2 ) 0.8 (PbTe) 0.2 Preparation of single crystal: Will be loaded with (AgSbTe 2 ) 0.8 (PbTe) 0.2 A polycrystalline quartz crucible is placed in a vertical growth furnace. The interior of the furnace chamber of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone from top to bottom. The temperature of the melting zone is set to 1100°C; the temperature range of the crystal growth zone is set to 650-900°C, and the temperature of the crystal growth zone is set to decrease by 30°C / cm from top to bottom; the temperature of the annealing zone is set to 500°C. After the temperature in the vertical growth furnace reaches the preset target, the quartz crucible is controlled by the lifter to begin to descend from the melting zone position at the top of the vertical growth furnace cavity, and passes through the melting zone, crystal growth zone and annealing zone in turn during the descent. The residence time of the quartz crucible in the melting zone is 10h; the single crystal growth rate of the material in the crystal growth zone is 1.5mm / h by controlling the descent speed; the residence time of the quartz crucible in the annealing zone is 15h; after the annealing treatment is completed, it is cooled to room temperature to obtain a large size (AgSbTe 2 ) 0.8 (PbTe) 0.2 Thermoelectric semiconductor single crystal, the chemical composition of this material is (AgSbTe 2 ) 0.8 (PbTe) 0.2 , single crystal, diameter 17mm, length 30mm.

[0047] The large size (AgSbTe 2 ) 0.8 (PbTe) 0.2 The thermoelectric properties of thermoelectric semiconductor single crystals were tested, and the results are shown in the following table: Table 3 From the comparison of the data in the above table, it can be seen that the large size (AgSbTe 2 ) 0.8 (PbTe) 0.2 Thermoelectric semiconductor single crystal, which is AgSbTe2 Compared with the thermoelectric performance of thermoelectric semiconductor single crystals, its thermal optimum value meets the target value of 0.6-0.8 in the temperature range of 450K-600K, and the thermal optimum value of Example 7 is more stable at different temperatures in the range of 450K-600K. It can be seen that the doping of an appropriate amount of Pb element is beneficial to further improve the stability of the thermal optimum value of the single crystal material in the above-mentioned temperature range of 450K-600K.

[0048] Example 8 (AgSbTe 2 ) 0.85 (GeTe) 0.15 ) A method for preparing a large-sized AgSbTe-based thermoelectric semiconductor single crystal, which specifically comprises the following steps: 1)(AgSbTe 2 ) 0.85 (GeTe) 0.15 Preparation of polycrystals: According to (AgSbTe 2 ) 0.85 (GeTe) 0.15 The raw materials (Ag, Sb, Te and Ge) were placed in a quartz crucible (30 cm in length, 17 mm in diameter, with a conical bottom and a taper of 18-54°) and mixed evenly, and then vacuumed and sealed until the vacuum degree reached 10 -3 Then the quartz crucible was placed in a swing furnace, and the swing furnace was controlled to heat up to 1100°C at a heating rate of 8°C / min. During this period, the swing rate of the swing furnace was 25r / min, and the swing time was 2h, until the raw materials were fully melted and mixed, and then cooled to obtain (AgSbTe 2 ) 0.85 (GeTe) 0.15 Polycrystalline.

[0049] 2)(AgSbTe 2 ) 0.85 (GeTe) 0.15 Preparation of single crystal: Will be loaded with (AgSbTe 2 ) 0.85 (GeTe) 0.15A polycrystalline quartz crucible is placed in a vertical growth furnace. The interior of the furnace chamber of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone from top to bottom. The temperature of the melting zone is set to 1100°C; the temperature range of the crystal growth zone is set to 650-900°C, and the temperature of the crystal growth zone is set to decrease by 30°C / cm from top to bottom; the temperature of the annealing zone is set to 500°C. After the temperature in the vertical growth furnace reaches the preset target, the quartz crucible is controlled by the lifter to begin to descend from the melting zone position at the top of the vertical growth furnace cavity, and passes through the melting zone, crystal growth zone and annealing zone in turn during the descent. The residence time of the quartz crucible in the melting zone is 12h; the single crystal growth rate of the material in the crystal growth zone is 1.5mm / h by controlling the descent speed; the residence time of the quartz crucible in the annealing zone is 15h; after the annealing treatment is completed, it is cooled to room temperature to obtain a large size (AgSbTe 2 ) 0.85 (GeTe) 0.15 Thermoelectric semiconductor single crystal, the chemical composition of this material is (AgSbTe 2 ) 0.85 (GeTe) 0.15 , single crystal, diameter 30mm, length 17mm.

[0050] The large size (AgSbTe 2 ) 0.85 (GeTe) 0.15 The thermoelectric properties of thermoelectric semiconductor single crystals were tested, and the results are shown in the following table: Table 4 From the comparison of the data in the above table, it can be seen that the large size (AgSbTe 2 ) 0.85 (GeTe) 0.15 Thermoelectric semiconductor single crystal, which is AgSbTe 2 Compared with the thermoelectric performance of thermoelectric semiconductor single crystals, its thermal optimum value meets the target value of 0.6-0.8 in the temperature range of 450K-600K, and the thermal optimum value of Example 8 is more stable at different temperatures in the range of 450K-600K. It can be seen that the doping of an appropriate amount of Pb element is beneficial to further improve the stability of the thermal optimum value of the single crystal material in the above-mentioned temperature range of 450K-600K.

[0051] Example 9 (adding seed crystals) A method for preparing a large-sized AgSbTe-based thermoelectric semiconductor single crystal, which specifically comprises the following steps: 1) AgSbTe 2 Preparation of polycrystals: According to AgSbTe 2The raw materials (Ag, Sb, Te) were placed in a quartz crucible (50 cm in length, 35 mm in diameter, conical bottom, 36° in taper) and mixed evenly. The crucible was evacuated and sealed until the vacuum degree reached 10 -3 Then the quartz crucible is placed in a swing furnace, and the swing furnace is controlled to heat up to 1200°C at a heating rate of 6°C / min. During this period, the swing rate of the swing furnace is 30r / min, and the swing time is 1h, until all the raw materials are fully melted and mixed, and then cooled to obtain AgSbTe 2 Polycrystalline.

[0052] 2) AgSbTe 2 Preparation of single crystal: Will be equipped with AgSbTe 2 The polycrystalline quartz crucible is placed in a vertical growth furnace (the quartz crucible is filled with AgSbTe 2 Single crystal seed crystal, the amount is 10 grams). Among them, the furnace chamber of the vertical growth furnace is divided into a melting zone, a crystal growth zone and an annealing zone from top to bottom. Among them, the temperature of the melting zone is set to 1100°C; the temperature range of the crystal growth zone is set to 650-900°C, and the temperature of the crystal growth zone is set to decrease by 30°C / cm from top to bottom; the temperature of the annealing zone is set to 400°C. After the temperature in the vertical growth furnace reaches the preset target, the quartz crucible is controlled by the elevator to begin to descend from the melting zone position at the top of the vertical growth furnace cavity, and during the descent, it passes through the melting zone, crystal growth zone and annealing zone in turn. Among them, the residence time of the quartz crucible in the melting zone is 8-15h; the single crystal growth rate of the material in the crystal growth zone is 2mm / h by controlling the descent speed; the residence time of the quartz crucible in the annealing zone is 15h; after completing the annealing treatment, it is cooled to room temperature to obtain a large-size AgSbTe 2 Thermoelectric semiconductor single crystal, the chemical composition of this material is AgSbTe 2 , single crystal, diameter 17mm, length 30mm.

[0053] The large-sized AgSbTe obtained in Example 9 2 The thermoelectric properties of thermoelectric semiconductor single crystals were tested, and the results are shown in the following table: Table 5 From the comparison of the data in the above table, it can be seen that the large-sized AgSbTe obtained in Example 9 2 Thermoelectric semiconductor single crystal, its thermal good electrical properties meet the target value of 0.6-0.8 in the temperature range of 450K-600K.

[0054] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0055] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal, characterized in that include: 1) Mix and melt the raw materials, and then cool them to obtain silver antimony tellurium-based polycrystals; 2) Placing a sealed container containing silver antimony tellurium-based polycrystals in a vertical growth furnace, controlling the container to descend, and passing through a melting zone, a crystal growth zone, and an annealing zone in sequence; wherein, the temperature of the melting zone is 950-1100°C; the temperature of the crystal growth zone is 650-900°C, and the temperature decreases from top to bottom by 20-40°C / cm, and the single crystal growth rate is 1-3mm / h; the temperature of the annealing zone is 300-500°C; and finally, a large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal with a thermoelectric figure of merit zT value of 0.6-0.8 in the range of 450-600K, a diameter of 10-80mm, and a length of 10-100mm is obtained.

2. The preparation method according to claim 1, characterized in that: In step 2), the composition of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is (AgSbTe2) x (PbTe) 1-x or (AgSbTe2) x (GeTe) 1-x ; where x=0-0.

9.

3. The preparation method according to claim 2, characterized in that: In step 2), the composition of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is AgSbTe2, (AgSbTe2) x (PbTe) 1-x or (AgSbTe2) x (GeTe) 1-x ; where x=0.8-0.

85.

4. The preparation method according to claim 1, characterized in that: In step 2), the diameter of the large-sized silver antimony tellurium-based thermoelectric semiconductor single crystal is 15-40 mm.

5. The preparation method according to claim 1, characterized in that: In step 1), each raw material is placed in a container and sealed in vacuum, and then placed in a vertical melting furnace or a swing furnace for melting, and then cooled to obtain silver antimony tellurium-based polycrystals.

6. The preparation method according to claim 5, characterized in that: In step 1), the vacuum degree of the vacuum seal is 10 -2 -10 -3 pa; the melting temperature is 1050-1200°C, and the heating rate is 2-10°C / min.

7. The preparation method according to claim 6, characterized in that: In step 1), the swing rate of the swing furnace is 10-30 r / min, and the swing time is 0.5-3 h.

8. The preparation method according to claim 1, characterized in that: In step 2), the residence time of the silver antimony tellurium based polycrystal in the melting zone is 8-15 hours.

9. The preparation method according to claim 1, characterized in that: In step 2), the residence time in the annealing zone is 8-20 hours.

10. The preparation method according to claim 1, characterized in that: In step 2), a seed crystal is added during the single crystal growth process.

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