Thermoelectric crystal bismuth selenide, preparation method thereof, and thermoelectric conversion device

Abstract

The present invention discloses a thermoelectric crystal Bi2Se3 and its preparation method and thermoelectric conversion device, wherein the preparation method comprises: (1) mixing elemental Bi and elemental Se and sealing them in a pointed quartz tube, then placing the pointed quartz tube at a first predetermined position below the growth point position in a Bridgman furnace, setting a first predetermined temperature and keeping it warm for a first predetermined time, wherein the Bridgman furnace includes a lower temperature zone, a partition zone, a middle temperature zone and an upper temperature zone from bottom to top, and the growth point position is located within a region 2 mm above the partition zone; (2) placing the pointed quartz tube at a second predetermined position above the growth point position in the Bridgman furnace, setting a second predetermined temperature and keeping it warm for a second predetermined time, and finally lowering the pointed quartz tube to a third predetermined position and annealing to obtain the thermoelectric crystal Bi2Se3. The thermoelectric crystal Bi2Se3 obtained by this method has excellent thermoelectric performance, and its power factor PF reaches 1300 μW / m·K at 50°C. 2 .

Description

Technical Field

[0001] The present invention belongs to the field of energy materials, and in particular relates to a thermoelectric crystal Bi2Se3 and a preparation method thereof and a thermoelectric conversion device. Background Art

[0002] With the continuous development of human society, energy and environmental problems are becoming increasingly serious. Human society's over-reliance on fossil energy has further stimulated the development of new energy technologies worldwide. Thermoelectric conversion technology is the most direct and simple technology that can realize the direct conversion of heat energy and electrical energy. It can convert solar energy, geothermal energy, and waste heat generated by transportation, industrial production and residents' lives into electricity. The efficiency of thermoelectric power generation is mainly determined by the dimensionless performance figure of merit ZT of the material, ZT = (S 2 σ / κ)T. Thus, achieving high thermoelectric efficiency at a certain temperature T often requires a large thermoelectric potential S, a high electrical conductivity σ, and a low thermal conductivity κ. Therefore, developing thermoelectric materials with high thermoelectric figures of merit is of great significance for alleviating current energy and environmental problems.

[0003] Currently, the most widely used thermoelectric semiconductor materials are tellurium (Te)-based materials (Bi2Te3, PbTe), which have a wide range of applications in thermoelectric power generation and room-temperature refrigeration. However, Te is a rare element in the Earth's crust, with an abundance of only one billionth of a percent. As Te-containing materials become available in large quantities, the cost of Te will rise sharply. Therefore, it is necessary to develop high-performance thermoelectric materials that do not contain Te. High-performance thermoelectric materials such as SnSe, Cu2Se-based ionic semiconductors, and PbSe-based thermoelectric semiconductors have attracted great interest among researchers. Bi2Se3 is a topological insulator and a sister crystal of the room-temperature thermoelectric semiconductor Bi2Te3. Bi2Se3-based materials have important applications in superconductivity, optoelectronics, and other fields. However, due to their low thermoelectric figure of merit, their thermoelectric properties have not been further studied. Summary of the Invention

[0004] The present invention aims to solve, at least to some extent, one of the technical problems in the related art. To this end, one object of the present invention is to provide a thermoelectric crystal Bi2Se3, a preparation method thereof, and a thermoelectric conversion device. The thermoelectric crystal Bi2Se3 obtained by this method has excellent thermoelectric properties and a power factor (PF) of 1300 μW / m·K at 50°C. 2 .

[0005] In one aspect of the present invention, a method for preparing a thermoelectric crystal Bi2Se3 is provided. According to an embodiment of the present invention, the method comprises:

[0006] (1) mixing elemental Bi and elemental Se and sealing them in a pointed quartz tube, then placing the pointed quartz tube at a first predetermined position below the growth point in a Bridgman furnace, setting a first predetermined temperature and maintaining the temperature for a first predetermined time, wherein the Bridgman furnace includes, from bottom to top, a lower temperature zone, a partition zone, a middle temperature zone, and an upper temperature zone, and the growth point is located within a region 2 mm above the partition zone;

[0007] (2) placing the pointed quartz tube at a second predetermined position above the growth point in the Bridgman furnace, setting a second predetermined temperature and keeping the temperature for a second predetermined time, and finally lowering the pointed quartz tube to a third predetermined position and annealing to obtain the thermoelectric crystal Bi2Se3.

[0008] According to the method for preparing the thermoelectric crystal Bi2Se3 according to an embodiment of the present invention, elemental Bi and elemental Se are mixed and sealed in a pointed quartz tube, which is then supplied to a Bridgman furnace. By optimizing the position of the pointed quartz tube in the Bridgman furnace and the temperature fields in the lower, middle, and upper temperature zones of the Bridgman furnace, the obtained thermoelectric crystal Bi2Se3 has excellent thermoelectric performance, and its power factor PF reaches 1300 μW / m·K at 50°C. 2 .

[0009] In addition, the method for preparing the thermoelectric crystal Bi2Se3 according to the above embodiment of the present invention may also have the following additional technical features:

[0010] In some embodiments of the present invention, in step (1), the first predetermined position is 50 to 70 mm below the growth point position, thereby ensuring that the obtained thermoelectric crystal Bi2Se3 has excellent hot spot performance.

[0011] In some embodiments of the present invention, in step (1), setting the first predetermined temperature and maintaining the temperature for the first predetermined time is performed as follows: setting the temperature of the intermediate temperature zone and the upper temperature zone to 800-850°C, setting the temperature of the lower temperature zone to 850-900°C, and maintaining the temperature for 12-24 hours. This ensures that the resulting thermoelectric crystal Bi2Se3 has excellent hot spot performance.

[0012] In some embodiments of the present invention, in step (2), the second predetermined position is 10 to 20 mm above the growth point position.

[0013] In some embodiments of the present invention, setting the second predetermined temperature and maintaining the temperature for the second predetermined time is performed as follows: setting the temperatures of the intermediate and upper temperature zones to 650-700°C, setting the temperature of the lower temperature zone to 530-550°C, and maintaining these temperatures for 12-24 hours. This ensures that the resulting thermoelectric crystal Bi2Se3 has excellent hotspot performance.

[0014] In some embodiments of the present invention, in step (2), the third predetermined position is the point where the melt in the pointed quartz tube drops 10 to 20 mm below the growth point. This ensures that the resulting thermoelectric crystal Bi2Se3 has excellent hotspot performance.

[0015] In some embodiments of the present invention, the pointed quartz crucible is rotated at a speed of 10 to 20 rpm, and the pointed quartz tube is lowered to the third predetermined position at a rate of 0.6 to 5 mm / h. This ensures that the resulting thermoelectric crystal Bi2Se3 has excellent hotspot performance.

[0016] In some embodiments of the present invention, in step (2), the annealing is performed by first cooling the intermediate temperature zone and the upper temperature zone to 500-550°C at a rate of 25-40 kJ / h, and then cooling the intermediate temperature zone, the upper temperature zone, and the lower temperature zone to room temperature at a rate of 25-40 kJ / h. This ensures that the resulting thermoelectric crystal Bi2Se3 has excellent hotspot performance.

[0017] In some embodiments of the present invention, the above method further includes, before sealing the mixture of the elemental Bi and the elemental Se into a pointed quartz tube, vacuuming and melting the mixture of the elemental Bi and the elemental Se in advance to obtain Bi2Se3 polycrystals, and sealing the Bi2Se3 polycrystals into a pointed quartz tube.

[0018] In some embodiments of the present invention, the elemental Bi and the elemental Se are placed in a round-end quartz crucible and then vacuumed to a pressure not higher than 1×10 -3 Pa.

[0019] In some embodiments of the present invention, the smelting is performed in a muffle furnace at 800-850° C. for 12-24 hours.

[0020] In some embodiments of the present invention, the temperature gradient of the isolation zone is 10-40 K / cm.

[0021] In some embodiments of the present invention, the height of the partition area is 30-50 mm.

[0022] In a second aspect, the present invention provides a thermoelectric crystal Bi2Se3. According to an embodiment of the present invention, the thermoelectric crystal Bi2Se3 is prepared using the above-mentioned method. As a result, the thermoelectric crystal Bi2Se3 has excellent thermoelectric performance, and its power factor PF reaches 1300μW / m·K at 50°C. 2 .

[0023] In a third aspect, the present invention provides a thermoelectric conversion device. According to an embodiment of the present invention, the thermoelectric conversion device is prepared using the aforementioned thermoelectric crystal Bi2Se3. As a result, the thermoelectric conversion device has a high thermoelectric conversion efficiency.

[0024] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0026] Figure 1 1 is a schematic flow chart of a method for preparing a thermoelectric crystal Bi2Se3 according to one embodiment of the present invention;

[0027] Figure 2 is a partial structural schematic diagram of the Bridgman furnace used in the present invention;

[0028] Figure 3 This is a photo of the thermoelectric crystal Bi2Se3 obtained in Example 1;

[0029] Figure 4 The XRD pattern of the thermoelectric crystal Bi2Se3 obtained in Example 1 is compared with the standard pattern of Bi2Se3;

[0030] Figure 5 1 is a curve showing the change of the conductivity of the thermoelectric crystal Bi2Se3 obtained in Example 1 with temperature;

[0031] Figure 6 is a curve showing the change of the Seebeck coefficient of the thermoelectric crystal Bi2Se3 obtained in Example 1 with temperature;

[0032] Figure 7 1 is a curve showing the change of the power factor of the thermoelectric crystal Bi2Se3 obtained in Example 1 with temperature;

[0033] Figure 8 This is a photo of the thermoelectric crystal Bi2Se3 obtained in Example 2;

[0034] Figure 9 is the XRD pattern of the thermoelectric crystal Bi2Se3 obtained in Example 2;

[0035] Figure 10 2 is a curve showing the change of conductivity of the thermoelectric crystal Bi2Se3 obtained in Example 2 with temperature;

[0036] Figure 11 is a curve showing the change of the Seebeck coefficient of the thermoelectric crystal Bi2Se3 obtained in Example 2 with temperature;

[0037] Figure 12 This is a curve showing the change of the power factor of the thermoelectric crystal Bi2Se3 obtained in Example 2 with temperature. DETAILED DESCRIPTION

[0038] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0039] In one aspect of the present invention, the present invention provides a method for preparing a thermoelectric crystal Bi2Se3. Figure 1 , the method comprising:

[0040] S100: Mixing elemental Bi and elemental Se and sealing them in a pointed quartz tube, then placing the pointed quartz tube in a Bridgman furnace at a first predetermined position below the growth point, setting a first predetermined temperature and keeping it warm for a first predetermined time.

[0041] refer to Figure 2 The lower end of the Bridgman furnace is open, and it includes a lower temperature zone 100, a partition zone 200, a medium temperature zone 300 and an upper temperature zone 400 from bottom to top, and the growth point position 10 is located in the area 2mm above the partition zone 200. Thermocouples 11 are provided in the lower temperature zone 100, the medium temperature zone 300 and the upper temperature zone 400, and the height of the partition zone 200 is 30 to 50 mm.

[0042] In this step, the elemental Bi and elemental Se are mixed in the required ratio of Bi2Se3 and then placed in a pointed quartz tube 12 (the tapered angle of the pointed quartz tube is 20-60°), and then vacuumed to a pressure of no more than 1×10 -3 After Pa, the tube is sealed. In order to fully melt the elemental Bi and elemental Se and drive out the gas in the melt and mix the melt evenly, the pointed quartz tube 12 is placed in the Bridgman furnace at a first predetermined position below the growth point position 10, that is, 50 to 70 mm below the growth point position, and the first predetermined temperature is set and kept warm for a first predetermined time. Specifically, the elemental Bi and elemental Se are both elemental particles or powders with a purity of 99.999%, and then vacuumed to no more than 1×10 -3The tube is sealed after Pa. Setting the first predetermined temperature and maintaining the temperature for the first predetermined time is performed as follows: the temperature of the middle temperature zone 300 and the upper temperature zone 400 is set to 800-850°C, the temperature of the lower temperature zone 100 is set to 850-900°C, and the temperatures are maintained for 12-24 hours, and the temperature gradient of the isolation zone 200 is 10-40K / cm, so that the bubbles in the melt in the pointed quartz tube 12 can be discharged to the top of the melt.

[0043] According to one embodiment of the present invention, elemental Bi and elemental Se may be mixed and then smelted in advance, and then the obtained Bi2Se3 polycrystals are sealed in a pointed quartz tube. Specifically, before the elemental Bi and elemental Se are mixed and sealed in the pointed quartz tube, the elemental Bi and elemental Se are pre-mixed according to the required ingredients of Bi2Se3 and loaded into a clean round-headed quartz crucible (with an inner diameter of 10 to 20 mm), and then vacuumed to a pressure of no more than 1×10 -3 After Pa, the tube is sealed, and the sealed round-head quartz crucible is placed in a well chamber muffle furnace and smelted at 800-850°C for 12-24 hours. The elemental Bi and elemental Se are melted to obtain Bi2Se3 polycrystals. The obtained Bi2Se3 polycrystals are cooled to room temperature and then sealed in a pointed quartz tube, and finally the pointed quartz tube is placed in a Bridgman furnace.

[0044] It should be noted that the “first predetermined position, i.e., 50 to 70 mm below the growth point position 10 ” refers to the position where the material in the pointed quartz tube 12 is located 50 to 70 mm below the growth point position.

[0045] S200: placing the pointed quartz tube at a second predetermined position above the growth point in the Bridgman furnace, setting a second predetermined temperature and keeping the temperature for a second predetermined time, and finally lowering the pointed quartz tube to a third predetermined position for annealing.

[0046] In this step, the pointed quartz tube 12 is placed in a Bridgman furnace at a second predetermined position above the growth point position 10, and a second predetermined temperature is set and maintained for a second predetermined time. Finally, the pointed quartz tube 12 is lowered to a third predetermined position and then annealed to obtain a thermoelectric crystal Bi2Se3. Specifically, the second predetermined position is 10 to 20 mm above the growth point position 10, and the second predetermined temperature is set and maintained for a second predetermined time as follows: the temperature of the middle temperature zone 300 and the upper temperature zone 400 is set to 650 to 700°C, and the temperature of the lower temperature zone 100 is set to 530 to 550°C, and maintained for 12 to 24 hours to promote crystal growth in the pointed quartz tube 12. Then, with the rotation speed of the pointed quartz tube 12 being 10-20 rpm, the pointed quartz tube 12 is lowered to a third predetermined position at a descending rate of 0.6-5 mm / h. That is, annealing is started after the melt in the pointed quartz tube 12 descends to 10-20 mm below the growth point. The annealing is carried out by the following method: first, the middle temperature zone 300 and the upper temperature zone 400 are lowered to 500-550° C. at a rate of 25-40 k / h, and then the middle temperature zone 300, the upper temperature zone 400 and the lower temperature zone 100 are lowered to room temperature at a rate of 25-40 k / h, thereby eliminating the stress caused by temperature unevenness during crystal growth.

[0047] It should be noted that “the second predetermined position, i.e., 10 to 20 mm above the growth point position” refers to the position where the material in the pointed quartz tube 12 is located 10 to 20 mm above the growth point position.

[0048] According to the method for preparing the thermoelectric crystal Bi2Se3 according to an embodiment of the present invention, elemental Bi and elemental Se are mixed and sealed in a pointed quartz tube, which is then supplied to a Bridgman furnace. By optimizing the position of the pointed quartz tube in the Bridgman furnace and the temperature fields in the lower, middle, and upper temperature zones of the Bridgman furnace, the obtained thermoelectric crystal Bi2Se3 has excellent thermoelectric performance, and its power factor PF reaches 1300 μW / m·K at 50°C. 2 .

[0049] In a second aspect, the present invention provides a thermoelectric crystal Bi2Se3. According to an embodiment of the present invention, the thermoelectric crystal Bi2Se3 is prepared using the above-mentioned method. As a result, the thermoelectric crystal Bi2Se3 has excellent thermoelectric performance, and its power factor PF reaches 1300μW / m·K at 50°C. 2 It should be noted that the features and advantages described above for the method for preparing the thermoelectric crystal Bi2Se3 are also applicable to the thermoelectric crystal Bi2Se3, and will not be repeated here.

[0050] In its third aspect, the present invention provides a thermoelectric conversion device. According to an embodiment of the present invention, the thermoelectric conversion device is manufactured using the aforementioned thermoelectric crystal Bi2Se3. As a result, the thermoelectric conversion device exhibits high thermoelectric conversion efficiency. It should be noted that the features and advantages described above for the thermoelectric crystal Bi2Se3 and its preparation method also apply to this thermoelectric conversion device and will not be further elaborated here.

[0051] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0052] Example 1

[0053] The method for preparing the thermoelectric crystal Bi2Se3 comprises:

[0054] (1) Add the required ingredients of 30g Bi2Se3 into a clean round-head quartz crucible, seal the tube, and pre-evacuate to 1×10 -3 Pa below, then placed the quartz crucible containing elemental Bi and elemental Se in a pit muffle furnace, smelted at 800 ° C for 12 hours, and then cooled to room temperature to obtain Bi2Se3 polycrystals;

[0055] (2) The obtained Bi2Se3 polycrystals were sealed in a pointed quartz tube (the taper angle of the pointed quartz tube was 20°), and then the pointed quartz tube was placed 50-70 mm below the growth point in a Bridgman furnace. The temperatures of the upper, middle, and lower temperature zones were set to 800°C, 800°C, and 850°C, respectively, and kept at these temperatures for 12 h.

[0056] (3) The pointed quartz tube is raised to 20 mm above the growth point, and the temperatures of the upper temperature zone, the middle temperature zone and the lower temperature zone are set to 680 ° C, 680 ° C and 530 ° C respectively, and the temperature gradient of the isolation zone is controlled to 30 K / cm, and kept warm for 12 hours; then, with the rotation speed of the pointed quartz crucible being 10 rpm, the pointed quartz tube is lowered to the third predetermined position at a rate of 1 mm / h, that is, the melt in the pointed quartz tube is lowered to 10 mm below the growth point, and then annealing is started. The annealing conditions include lowering the temperature of the upper temperature zone and the middle temperature zone to 550 ° C at a rate of 25 K / h, and then lowering the middle temperature zone 300, the upper temperature zone 400 and the lower temperature zone 100 to room temperature at a rate of 25 k / h to obtain a thermoelectric crystal Bi2Se3, as shown in the photo. Figure 3 As shown, the XRD spectrum is Figure 4 The conductivity curve with temperature is shown as Figure 5 As shown in the figure, the Seebeck coefficient changes with temperature as shown in the figure. Figure 6 As shown, the power factor changes with temperature curve is as follows Figure 7shown.

[0057] Example 2

[0058] The method for preparing the thermoelectric crystal Bi2Se3 comprises:

[0059] (1) Elemental Bi and elemental Se were loaded into a pointed quartz tube (the tapered angle of the pointed quartz tube was 30°) according to the required ingredients of 25g Bi2Se3, and then vacuumed to 1×10 -3 The tube was sealed below Pa, and the pointed quartz tube was placed 50-70 mm below the growth point in the Bridgman furnace. The temperatures of the upper, middle and lower temperature zones were set to 800°C, 800°C and 850°C respectively, and kept warm for 12 h.

[0060] (2) The pointed quartz tube is raised to 10 mm above the growth point, and the temperatures of the upper temperature zone, the middle temperature zone and the lower temperature zone are set to 650 ° C, 650 ° C and 550 ° C respectively, and the temperature gradient of the isolation zone is controlled to 20 K / cm, and kept warm for 12 hours; then, with the rotation speed of the pointed quartz crucible being 15 rpm, the pointed quartz tube is lowered to the third predetermined position at a rate of 1 mm / h, that is, the melt in the pointed quartz tube is lowered to 10 mm below the growth point, and annealing is started. The annealing conditions include lowering the temperature of the upper temperature zone and the middle temperature zone to 550 ° C at a rate of 25 K / h, and then lowering the middle temperature zone 300, the upper temperature zone 400 and the lower temperature zone 100 to room temperature at a rate of 25 k / h to obtain a thermoelectric crystal Bi2Se3, as shown in the photo. Figure 8 As shown, the XRD spectrum is Figure 9 The conductivity curve with temperature is shown as Figure 10 As shown in the figure, the Seebeck coefficient changes with temperature as shown in the figure. Figure 11 As shown, the power factor changes with temperature curve is as follows Figure 12 shown.

[0061] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0062] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a thermoelectric crystal Bi2Se3, characterized in that: include: (1) After mixing elemental Bi and elemental Se, seal the mixture into a pointed quartz tube, and then place the pointed quartz tube at a first predetermined position below the growth point position in a Bridgman furnace, wherein the first predetermined position is 50 to 70 mm below the growth point position, and set a first predetermined temperature and keep the temperature for a first predetermined time, wherein the Bridgman furnace includes a lower temperature zone, a partition zone, a middle temperature zone, and an upper temperature zone from bottom to top, and the growth point position is located within a region 2 mm above the partition zone, and setting the first predetermined temperature and keeping the temperature for a first predetermined time is performed as follows: setting the temperature of the middle temperature zone and the upper temperature zone to 800 to 850°C, setting the temperature of the lower temperature zone to 850 to 900°C, and keeping the temperature for 12 to 24 hours; (2) placing the pointed quartz tube at a second predetermined position above the growth point position in the Bridgman furnace, the second predetermined position being 10 to 20 mm above the growth point position, and setting a second predetermined temperature and keeping it warm for a second predetermined time. Setting the second predetermined temperature and keeping it warm for a second predetermined time is carried out as follows: setting the temperature of the middle temperature zone and the upper temperature zone to 650 to 700°C, setting the temperature of the lower temperature zone to 530 to 550°C, and keeping it warm for 12 to 24 hours. Finally, lowering the pointed quartz tube to a third predetermined position and annealing it to obtain the thermoelectric crystal Bi2Se3. The third predetermined position is when the melt in the pointed quartz tube drops to 10 to 20 mm below the growth point position.

2. The method according to claim 1, characterized in that In step (2), with the rotation speed of the pointed quartz crucible being 10-20 rpm, the pointed quartz tube is lowered to the third predetermined position at a descending rate of 0.6-5 mm / h.

3. The method according to claim 1, characterized in that In step (2), the annealing is performed by the following method: first, the middle temperature zone and the upper temperature zone are lowered to 500-550°C at a rate of 25-40 k / h, and then the middle temperature zone, the upper temperature zone and the lower temperature zone are lowered to room temperature at a rate of 25-40 k / h.

4. The method according to claim 1, wherein It further includes that before the elemental Bi and the elemental Se are mixed and sealed in a pointed quartz tube, the elemental Bi and the elemental Se are mixed and then vacuumed for melting to obtain Bi2Se3 polycrystals, and the Bi2Se3 polycrystals are sealed in a pointed quartz tube.

5. The method according to claim 4, characterized in that Further comprising, the vacuuming comprises: placing the elemental Bi and the elemental Se into a round-headed quartz crucible and then vacuuming to a pressure not higher than 1×10 -3 Pa.

6. The method according to claim 4, characterized in that Further comprising, the smelting is carried out in a muffle furnace at 800-850° C. for 12-24 hours.

7. A thermoelectric crystal Bi2Se3, characterized in that: The thermoelectric crystal Bi2Se3 is prepared by the method described in any one of claims 1-6.

8. A thermoelectric conversion device, characterized in that: The thermoelectric conversion device is prepared using the thermoelectric crystal Bi2Se3 described in claim 7.

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