Cadmium telluride synthesis method

Abstract

A cadmium telluride synthesis method comprises the following steps: S1, mixing tellurium powder and cadmium powder in a molar ratio of 1:1, and using the mixed tellurium powder and cadmium powder as a material; S2, placing the material flatly into a horizontally placed reaction boat, and then placing the reaction boat into a horizontally placed quartz tube; S3, evacuating the quartz tube and sealing the tube; S4, fixing the sealed quartz tube horizontally and making the fixed sealed quartz tube concentric and coaxial with a heating zone; S5, heating the heater of a heating mechanism, heating the heating zone to 480-550°C and then keeping the temperature for 45-90 minutes; S6, the heating mechanism moves horizontally toward the quartz tube at a rate of 3-12 mm / min, and the quartz tube gradually enters the heating zone; S7, after the quartz tube completely enters the heating zone, the heating mechanism stops moving horizontally and continues to keep warm for 45-90 minutes; S8, the heater heats the heating zone to 1130-1150°C and keeps warm for 100-150 minutes; S9, the heater cools the heating zone to room temperature for annealing; S10, take out and break the quartz tube, take out the cadmium telluride polycrystalline ingot synthesized in the reaction boat, weigh it and store it in vacuum. Thus, the product yield is improved.

Description

Technical Field

[0001] The present disclosure relates to the field of cadmium telluride materials, and more particularly to a cadmium telluride synthesis method. Background Art

[0002] Cadmium telluride is a compound semiconductor material with an energy gap value of 1.45eV, and it is a direct energy gap, which is in the ideal solar cell energy gap range and has a good photoelectric conversion efficiency. Cadmium telluride thin-film solar cells have low manufacturing costs and high efficiency, and are suitable for large-scale industrialization. They are also used to make infrared modulators, HgCdTe substrates, infrared window field-induced light-emitting devices, photocells, infrared detection, X-ray detection, etc. At present, there are many methods for synthesizing cadmium telluride, mainly using a mixture of tellurium powder and cadmium powder. Chinese invention patent application publication number CN103818886A published on May 28, 2014 discloses a method for preparing cadmium telluride, which comprises mixing tellurium powder and cadmium powder in a molar ratio of 1:1, placing the mixture in a graphite boat, placing the mixture in a synthesis furnace, exhausting the air, and heating the mixture in three stages for one synthesis; Chinese invention patent application publication number CN103420346A published on December 4, 2013 discloses a method for preparing cadmium telluride, which comprises mixing tellurium powder and cadmium powder in a molar ratio of 1:1, placing the mixture in a graphite boat, placing the mixture in a quartz tube in a synthesis furnace, exhausting the air, and heating the mixture in three stages for one synthesis; since tellurium powder and cadmium powder react violently, splashing may even occur, resulting in waste of cadmium telluride materials and a low yield of the synthesized product. Summary of the invention

[0003] In view of the problems existing in the background technology, the purpose of the present disclosure is to provide a cadmium telluride synthesis method, which can effectively reduce the severity of the cadmium telluride synthesis reaction, reduce the material loss caused by material splashing during cadmium telluride synthesis, and improve the product yield of cadmium telluride polycrystals.

[0004] Thus, a cadmium telluride synthesis method comprises the following steps: S1, mixing tellurium powder and cadmium powder in a molar ratio of 1:1, and using the mixed tellurium powder and cadmium powder as a material; S2, placing the material flatly into a horizontally placed reaction boat, and then placing the reaction boat into a horizontally placed quartz tube; S3, evacuating the quartz tube and sealing the tube; S4, fixing the sealed quartz tube horizontally and making the fixed sealed quartz tube concentric and coaxial with the heating zone of the heating mechanism; S5, heating the heater of the heating mechanism, heating the heating zone to 480-550°C and then keeping the temperature for 45-90 min; S6, the heating mechanism moves horizontally toward the quartz tube at a rate of 3-12 mm / min, and the quartz tube gradually enters the heating zone; S7, after the quartz tube completely enters the heating zone, the heating mechanism stops horizontal movement and continues to keep warm for 45-90 min; S8, the heater heats the heating zone to 1130-1150°C and keeps warm for 100-150 min; S9, the heater cools down the heating zone and anneals it to room temperature; S10, take out and break the quartz tube, take out the cadmium telluride polycrystalline ingot synthesized in the reaction boat, weigh it and store it in a vacuum.

[0005] The beneficial effects of the present disclosure are as follows: In the cadmium telluride synthesis method according to the present disclosure, by setting step S6, the intensity of the cadmium telluride synthesis reaction can be effectively reduced, the material loss caused by material splashing during cadmium telluride synthesis can be reduced, and the product yield of cadmium telluride polycrystalline can be improved. In addition, by setting step S6, the risk of quartz tube cracking can also be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 The figure shows the process in which the heating mechanism moves relative to the quartz tube in the cadmium telluride synthesis method disclosed in the present invention so that the quartz tube enters the heating zone, wherein the dotted arrow shows the direction in which the heating mechanism moves horizontally toward the quartz tube, and the sealed quartz tube is shown concentrically and coaxially with the heating zone of the heating mechanism by the dotted line.

[0007] The following are the descriptions of the reference numerals:

[0008] 100 material 41 heating zone

[0009] 1 Reaction boat 411 first end

[0010] 2 Quartz tube 412 second end

[0011] 3 quartz bubble 42 heater

[0012] W welding part 43 insulation layer

[0013] 4 Heating mechanism 44 Insulation material DETAILED DESCRIPTION

[0014] The accompanying drawings show embodiments of the present disclosure, and it will be understood that the disclosed embodiments are merely examples of the present disclosure, and the present disclosure can be implemented in various forms. Therefore, the specific details disclosed herein should not be interpreted as limiting, but merely as the basis for the claims and as a representative basis for teaching ordinary technicians in the field to implement the present disclosure in various ways.

[0015] [Cadmium telluride synthesis method]

[0016] Reference Figure 1 According to the present disclosure, the cadmium telluride synthesis method comprises the steps of:

[0017] S1, mixing tellurium powder and cadmium powder in a molar ratio of 1:1, and the mixed tellurium powder and cadmium powder is used as material 100;

[0018] S2, placing the material 100 flatly into a horizontally placed reaction boat 1, and then placing the reaction boat 1 into a horizontally placed quartz tube 2;

[0019] S3, evacuate the quartz tube 2 and seal the tube;

[0020] S4, fixing the sealed quartz tube 2 horizontally and making the fixed sealed quartz tube 2 concentric and coaxial with the heating zone 41 of the heating mechanism 4;

[0021] S5, the heater 42 of the heating mechanism 4 heats the heating zone 41 to 480-550°C and then keeps the temperature for 45-90 minutes.

[0022] S6, the heating mechanism 4 moves horizontally toward the quartz tube 2 at a rate of 3-12 mm / min, and the quartz tube 2 gradually enters the heating zone 41;

[0023] S7, after the quartz tube 2 completely enters the heating zone 41, the heating mechanism 4 stops horizontal movement and continues to keep warm for 45-90 minutes;

[0024] S8, the heater 42 heats the heating zone 41 to 1130-1150°C and keeps the temperature for 100-150 minutes;

[0025] S9, the heater 42 cools down the heating area 41 to anneal to room temperature;

[0026] S10, taking out and breaking the quartz tube 2, taking out the cadmium telluride polycrystalline ingot synthesized in the reaction boat 1, weighing it and storing it in a vacuum.

[0027] In the cadmium telluride synthesis method according to the present disclosure, the setting of step S6 can effectively reduce the severity of the cadmium telluride synthesis reaction, reduce the material loss caused by material splashing during cadmium telluride synthesis, and improve the product yield of cadmium telluride polycrystalline. In addition, the setting of step S6 can also effectively reduce the risk of cracking of the quartz tube 2.

[0028] In one example, in step S1, the purity of the tellurium powder and the cadmium powder is 5N, and the particle size of the tellurium powder and the cadmium powder is less than 120 μm. The mixing of the tellurium powder and the cadmium powder can be performed in a homogenizer.

[0029] In one example, in step S2, the reaction boat 1 is a graphite boat or a quartz boat with the entire inner and outer surfaces coated with a carbon film.

[0030] In one example, in step S3, the quartz tube 2 is evacuated in a tube sealing furnace and the quartz tube 2 and the quartz sealing bubble 3 are sealed by spraying the quartz tube 2 at the welding position W with a hydrogen-oxygen flame so that the quartz tube 2 melts and sinks under vacuum and is welded together with the quartz sealing bubble 3.

[0031] In one example, in step S3, the vacuum is evacuated to 2.0×10 -2 Below Pa.

[0032] In step S4, the sealed quartz tube 2 may be fixed horizontally in any suitable manner, such as by horizontal vacuum adsorption.

[0033] In one example, in step S5, the heater 42 of the heating mechanism 4 heats the heating zone 41 from room temperature to 500°C in 30 minutes, and then keeps the temperature for 60 minutes.

[0034] In one example, in step S6 , the heating mechanism 4 moves horizontally toward the quartz tube 2 at a rate of 5-10 mm / min.

[0035] In step S6, the mechanism for driving the heating mechanism 4 to move horizontally may be any suitable mechanism, such as a linear motor, a linear cylinder or a hydraulic cylinder, a screw nut transmission mechanism, etc.

[0036] In one example, in step S7, the temperature is kept at room temperature for 60 minutes.

[0037] In one example, in step S8 , the heater 42 raises the temperature of the heating zone 41 from 500° C. to 1150° C. within 60 minutes and keeps the temperature for 120 minutes.

[0038] In one example, in step S9, the heater 42 of the heating mechanism 4 reduces the temperature of the heating zone 41 from 1150°C to 500°C within 300 minutes, keeps the temperature for 60 minutes, then turns off the heating, and the heating zone 41 cools naturally to room temperature.

[0039] In one example, in step S10, the heating mechanism 4 moves horizontally in the opposite direction away from the quartz tube 2 so that the heating mechanism 4 is separated from the quartz tube 2. After the quartz tube 2 is completely separated from the heating mechanism 4, the horizontal fixation of the quartz tube 2 is released to achieve the removal of the quartz tube 2.

[0040] like Figure 1As shown, in one example, the heater 42 of the heating mechanism 4 surrounds the heating zone 41 to circumferentially close the heating zone 41, and the heating zone 41 has a first end 411 and a second end 412 opposite in horizontal directions, the first end 411 is closed, and the second end 412 faces the quartz tube 1 and is open.

[0041] like Figure 1 As shown, in one example, the heating mechanism 4 also includes a thermal insulation layer 43 and a thermal insulation material 44; the thermal insulation layer 43 is arranged at the first end 411 of the heating zone 41 and is located at the corresponding end of the heater 42; the thermal insulation material 44 is annularly arranged at the second end 412 of the heating zone 41 and is located at the corresponding end of the heater 42.

[0042] [test]

[0043] Example 1

[0044] The cadmium telluride synthesis method comprises the steps of:

[0045] S1, 1595 g of tellurium powder and 1405 g of cadmium powder with a molar ratio of 1:1 and a purity of 5N and a particle size of less than 120 μm are mixed in a homogenizer, and the mixed tellurium powder and cadmium powder are used as material 100;

[0046] S2, evenly spread the material 100 into a horizontally placed reaction boat 1, and then put the reaction boat 1 into a horizontally placed quartz tube 2, where the reaction boat 1 is a quartz boat with the entire inner and outer surfaces coated with a carbon film;

[0047] S3, evacuate the quartz tube 2 to 2.0×10 -2 Pa and the quartz tube 2 and the quartz bubble 3 are sealed by spraying the quartz tube 2 with an oxyhydrogen flame at the welding position W so that the quartz tube 2 melts and sinks under vacuum and is welded with the quartz bubble 3. Note that the quartz tube 2 must not be tilted in this step to prevent the material 100 and the reaction boat 1 from moving in the quartz tube 2;

[0048] S4, the sealed quartz tube 2 is fixed horizontally and the fixed sealed quartz tube 2 is concentric and coaxial with the heating zone 41 of the heating mechanism 4. Note that the quartz tube 2 must not be tilted in this step to prevent the material 100 and the reaction boat 1 from moving in the quartz tube 2. The heating mechanism 4 adopts Figure 1 The sealed quartz tube 2 is fixed horizontally by horizontal vacuum adsorption;

[0049] S5, the heater 42 of the heating mechanism 4 heats the temperature from room temperature to 500° C. in 30 minutes, and then keeps the temperature for 60 minutes;

[0050] S6, the heating mechanism 4 moves horizontally toward the quartz tube 2 at a rate of 10 mm / min, and the quartz tube 2 gradually enters the heating zone 41. The mechanism for driving the heating mechanism 4 to move horizontally adopts a linear cylinder;

[0051] S7, after the quartz tube 2 completely enters the heating zone 41, the heating mechanism 4 stops horizontal movement and continues to keep warm for 60 minutes;

[0052] S8, the heater 42 raises the temperature of the heating zone 41 from 500°C to 1150°C within 60 minutes and keeps the temperature for 120 minutes;

[0053] S9, the heater 42 lowers the temperature of the heating zone 41 from 1150°C to 500°C within 300 minutes, keeps the temperature for 60 minutes, then turns off the heating, and the heating zone 41 cools naturally to room temperature;

[0054] S10, taking out and breaking the quartz tube 2, taking out the cadmium telluride polycrystalline ingot synthesized in the reaction boat 1, weighing it and storing it in a vacuum.

[0055] The cadmium telluride polycrystalline ingot obtained in step 10 weighs 2967.2 g.

[0056] Example 2

[0057] Except that the speed of 5 mm / min is adopted in step S6, the rest is the same as that in Example 1. The cadmium telluride polycrystalline ingot obtained in step 10 of Example 2 weighs 2973.5 g.

[0058] Comparative Example 1

[0059] The above steps are the same as those in Example 1 except that step S4 is changed to "directly place the sealed quartz tube 2 into the heating zone 41", step S6 is cancelled, and step S7 is changed to "after the quartz tube 2 completely enters the heating zone 41, the heating mechanism 4 continues to keep the temperature for 60 minutes".

[0060] The cadmium telluride polycrystalline ingot obtained in step S10 weighs 2516.8 g, and it is found that a lot of materials splash out of the reaction boat 1 and stick to the inner wall of the quartz tube 2 during the synthesis.

[0061] Comparative Example 2

[0062] Except that step S4 is changed to "directly place the sealed quartz tube 2 into the heating zone 41", step S6 is cancelled, and step S7 is changed to "after the quartz tube 2 completely enters the heating zone 41, the heating mechanism 4 continues to keep warm for 60 minutes", steps S1 to S3, step S5 and step S8 are the same as in Example 1. However, in Comparative Example 2, when the temperature is raised to 1150°C in step S8, yellow smoke is seen to be emitted from the second end 412 of the heating zone 41 of the heating structure 4, and thus, steps S9 and S10 cannot be performed. After the heater 42 is cooled down, it can be observed that the quartz tube 2 is cracked at the welding position W during synthesis.

[0063] Table 1 shows the materials, cadmium telluride polycrystalline ingots and yields of Examples 1-2 and Comparative Examples 1-2.

[0064] Table 1 Materials, cadmium telluride polycrystalline ingots and yields of Examples 1-2 and Comparative Examples 1-2

[0065] Material(g) Cadmium telluride polycrystalline ingot(g) Yield (%) Example 1 3000 2967.2 98.91 Example 2 3000 2973.5 99.12 Comparative Example 1 3000 2516.8 83.89 Comparative Example 2 3000 Broken pipe, cannot be obtained Broken pipe, cannot be obtained

[0066] It can be seen from the comparison between Example 1-2 and Comparative Example 1 that the heating mechanism 4 in step S6 moves horizontally toward the quartz tube 2 at a rate of 10 mm / min and 5 mm / min, and the quartz tube 2 gradually enters the heating zone 41", which is beneficial to the synthesis of the cadmium telluride polycrystalline ingot and to improve the yield of the cadmium telluride polycrystalline ingot.

[0067] It can be seen from the comparison between Examples 1-2 and Comparative Example 1 that the heating mechanism 4 in step S6 moves horizontally toward the quartz tube 2 at a rate of 10 mm / min and 5 mm / min, and the quartz tube 2 gradually enters the heating zone 41", which can effectively reduce the risk of the quartz tube 2 cracking.

[0068] It can be seen from the comparison of Examples 1-2 that the slower the speed at which the heating mechanism 4 in step S6 moves horizontally toward the quartz tube 2 is, the more beneficial it is to improve the yield of the cadmium telluride polycrystalline ingot.

[0069] The above detailed description is used to describe multiple exemplary embodiments, but this document is not intended to be limited to the explicitly disclosed combinations. Therefore, unless otherwise stated, the various features disclosed herein can be combined together to form multiple additional combinations that are not shown for the sake of simplicity.

Claims

1. A method for synthesizing cadmium telluride, characterized in that: Includes steps: S1, mixing tellurium powder and cadmium powder in a molar ratio of 1:1, and the mixed tellurium powder and cadmium powder is used as material (100); S2, placing the material (100) flatly into a horizontally placed reaction boat (1), and then placing the reaction boat (1) into a horizontally placed quartz tube (2); S3, evacuating the quartz tube (2) and sealing the tube; S4, fixing the sealed quartz tube (2) horizontally and making the fixed sealed quartz tube (2) concentric and coaxial with the heating zone (41) of the heating mechanism (4), the heater (42) of the heating mechanism (4) surrounds the heating zone (41) to circumferentially seal the heating zone (41), the heating zone (41) having a first end (411) and a second end (412) in opposite horizontal directions, the first end (411) being closed, and the second end (412) facing the quartz tube (2) and being open; S5, the heater (42) of the heating mechanism (4) heats the heating zone (41) to 480-550° C. and then keeps the temperature for 45-90 minutes; S6, the heating mechanism (4) moves horizontally toward the quartz tube (2) at a rate of 3-12 mm / min, and the quartz tube (2) gradually enters the heating zone (41); S7, after the quartz tube (2) completely enters the heating zone (41), the heating mechanism (4) stops horizontal movement and continues to keep the temperature for 45-90 minutes; S8, the heater (42) heats the heating zone (41) to 1130-1150°C and keeps the temperature for 100-150 minutes; S9, the heater (42) cools down the heating zone (41) to anneal to room temperature; S10, taking out and breaking the quartz tube (2), taking out the cadmium telluride polycrystalline ingot synthesized in the reaction boat (1), weighing it and storing it in a vacuum; in, In step S1, the purity of tellurium powder and cadmium powder is 5N, and the particle size of tellurium powder and cadmium powder is less than 120 μm; In step S2, the reaction boat (1) is a quartz boat with the entire inner and outer surfaces coated with a carbon film; In step S3, the vacuum is evacuated to 2.0×10 -2 Below Pa; In step S5, the heater (42) of the heating mechanism (4) is heated to raise the temperature of the heating zone (41) from room temperature to 500°C in 30 minutes, and then the temperature is kept at this temperature for 60 minutes; In step S7, the temperature is kept for 60 minutes; In step S8, the heater (42) raises the temperature of the heating zone (41) from 500°C to 1150°C within 60 minutes and keeps the temperature for 120 minutes; In step S9, the heater (42) of the heating mechanism (4) reduces the temperature of the heating zone (41) from 1150°C to 500°C within 300 minutes, keeps the temperature for 60 minutes, then turns off the heating, and the heating zone (41) cools naturally to room temperature.

2. The cadmium telluride synthesis method according to claim 1, characterized in that: In step S10, the heating mechanism (4) moves horizontally in the reverse direction away from the quartz tube (2) so that the heating mechanism (4) is separated from the quartz tube (2). After the quartz tube (2) is completely separated from the heating mechanism (4), the horizontal fixation of the quartz tube (2) is released, thereby achieving the removal of the quartz tube (2).

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