Cadmium telluride polycrystal purification method
By using low-purity tellurium blocks as solvents, and using the multiple lifting and descent processes of the heating furnace, multiple purification of cadmium telluride polycrystalline is achieved, solving the problem of high cost and improving the purity and product quality of cadmium telluride polycrystallineline.
Patent Information
- Application Number
- CN202510424863.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-07
- Publication Date
- 2025-07-29
AI Technical Summary
The prior art has high costs in improving the purity of cadmium telluride polycrystalline, and it is difficult to improve the purity while reducing the cost.
Low-purity tellurium blocks are used as solvents, and the cadmium telluride polycrystalline is supersaturated and precipitated in the tellurium solvent by lifting and decreasing multiple times in the heating furnace to form a dense microscopic level, achieving multiple purifications and reducing the purity requirements of tellurium blocks.
While reducing costs, it significantly improves the purity of cadmium telluride polycrystalline, improves the quality of the product, and reaches 7N, reducing material costs.
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Figure CN120384330A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to the field of semiconductor materials, and more particularly to a method for purifying cadmium telluride polycrystals. Background Art
[0002] Cadmium telluride is a compound semiconductor material with a band gap value of 1.45 eV and a direct band gap, which is in the ideal solar cell band gap range and has good photoelectric conversion efficiency. Cadmium telluride thin film solar cells have low manufacturing costs and high efficiency, are suitable for large-scale industrialization, and are also used to manufacture infrared modulators, HgCdTe substrates, infrared window field emission devices, photovoltaic cells, infrared detection, X-ray detection, etc. The higher the purity of cadmium telluride polycrystals, the more beneficial it is to improve the quality of products prepared using cadmium telluride polycrystals. Therefore, it is necessary to further develop cadmium telluride polycrystals with improved purity. Of course, when obtaining cadmium telluride polycrystals with improved purity, the lower the cost, the better. Summary of the Invention
[0003] In view of the problems existing in the background art, the purpose of the present disclosure is to provide a method for purifying cadmium telluride polycrystals, which can improve the purity of cadmium telluride polycrystals while reducing costs.
[0004] Accordingly, a method for purifying cadmium telluride polycrystals includes the following steps: S1, loading tellurium blocks at the bottom of a vertically placed quartz tube; S2, loading a cadmium telluride polycrystalline ingot with a purity higher than that of the tellurium blocks into the quartz tube, with the cadmium telluride polycrystalline ingot located above the tellurium blocks; S3, installing a flange on the opening of the quartz tube, evacuating the inside of the quartz tube by a vacuum pump via a connecting pipe on the flange, and then closing the valve on the connecting pipe to maintain the vacuum inside the quartz tube; S4, installing the quartz tube with the flange in a vertical position into the heater of a heating furnace, with the lowest position of the tellurium blocks in the quartz tube not lower than and adjacent to the annular heating zone of the heater; S5, the heating furnace runs a heating program, heating the heating zone from room temperature to a temperature higher than the melting point of tellurium but lower than the melting point of cadmium telluride, and maintaining a constant temperature to completely melt at least the tellurium blocks inside the quartz tube to form a molten zone of tellurium solvent; S6, performing the first lift of the heater to move the heating zone upward, thereby moving the molten zone inside the quartz tube upward until the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube; S7, performing the descent of the heater to move the molten zone inside the quartz tube downward until the molten zone is at the bottom of the material inside the quartz tube; S8, performing the second lift of the heater to move the heating zone upward, thereby moving the molten zone inside the quartz tube upward until the molten zone is at the top of the material inside the quartz tube; S9, after the second lift of the heater ends, turning off the heating program, and removing the quartz tube after the furnace body of the heating furnace cools down to room temperature; S10, removing the flange, pouring out the product, with the top of the product being a tellurium solvent block and below the tellurium solvent block being the purified cadmium telluride polycrystalline material; S11, separating the tellurium solvent block and the purified cadmium telluride polycrystalline material to obtain the purified cadmium telluride polycrystalline material; S12, sampling and detecting impurities in the purified cadmium telluride polycrystalline material.
[0005] The beneficial effects of the present disclosure are as follows.
[0006] In the cadmium telluride polycrystalline purification method according to the present disclosure, before the first lift of the heater in step S6, at least all the tellurium blocks in the quartz tube in step S5 are melted to form a molten zone of tellurium solvent. During the first lift in step S6, as the heater is lifted, the cadmium telluride polycrystalline ingot above the molten zone will enter the heating zone of the heater, and then continuously dissolve into the molten zone (i.e., the molten zone of tellurium solvent) at the upper edge of the molten zone, and finally reach a saturated steady state in the molten zone. The lower edge of the molten zone will leave the heating zone of the heater, and then the temperature decreases. The cadmium telluride polycrystal is supersaturated in the tellurium solvent, so it precipitates at a low temperature in a dense microscopic layer in units of molecules or grains. The precipitated dense microscopic layer continuously stacks below the molten zone to form a dense cadmium telluride polycrystalline material, thereby realizing the upward movement of the molten zone and the preliminary purification of the cadmium telluride polycrystal. During the descent in step S7, as the heater descends, the cadmium telluride polycrystalline material below the molten zone will enter the heating zone of the heater, and then continuously dissolve into the molten zone (i.e., the molten zone of tellurium solvent) at the lower edge of the molten zone, and finally reach a saturated steady state in the molten zone. The upper edge of the molten zone will leave the heating zone of the heater, and then the temperature decreases. The cadmium telluride polycrystal is supersaturated in the tellurium solvent, so it precipitates at a low temperature (i.e., the upper edge) in a dense microscopic layer in units of molecules or grains. The precipitated dense microscopic layer continuously stacks above the molten zone to form a dense cadmium telluride polycrystalline material, thereby realizing the downward movement of the molten zone and the secondary purification of the cadmium telluride polycrystal. During the second lift in step S8, like the first lift process, the upward movement of the molten zone and the tertiary purification of the cadmium telluride polycrystal are realized. In step S2, the purity of the tellurium block is lower than that of the cadmium telluride polycrystalline ingot. Compared with using a tellurium block with a purity not lower than that of the cadmium telluride polycrystalline ingot, the purity requirement of the tellurium block can be reduced, thereby reducing the material cost of the tellurium block. Thus, a tellurium block with a low purity can be used as the solvent for the molten zone to perform the three purifications of lift-descent-lift to obtain a cadmium telluride polycrystal with a higher purity after purification. In other words, through the cadmium telluride polycrystalline purification method of the present disclosure, the purity of the cadmium telluride polycrystal can be improved while reducing the cost, which is beneficial to improving the quality of products prepared using the cadmium telluride polycrystal. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Figure 1 is a schematic flowchart of a partial operation process of the cadmium telluride polycrystalline purification method according to the present disclosure.
[0008] Figure 2 is a schematic structural diagram of the product in the cadmium telluride polycrystalline purification method of the present disclosure.
[0009] Figure 3 shows a cross-sectional photograph of the product of Comparative Example 2. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0010] 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 construed as limiting, but only as the basis for the claims and as a representative basis for teaching those of ordinary skill in the art to implement the present disclosure in various ways.
[0011] [Cadmium Telluride Polycrystal Purification Method]
[0012] Referring to Figure 1 and Figure 2 , the cadmium telluride polycrystal purification method according to the present disclosure includes the steps of:
[0013] S1, loading tellurium blocks into the bottom of a vertically placed quartz tube;
[0014] S2, loading a cadmium telluride polycrystalline ingot with a purity higher than that of the tellurium blocks into the quartz tube, and the cadmium telluride polycrystalline ingot is located above the tellurium blocks.
[0015] S3, installing a flange on the opening of the quartz tube, evacuating the inside of the quartz tube by a vacuum pump via a connecting pipe on the flange, and then closing the valve on the connecting pipe to maintain the vacuum inside the quartz tube;
[0016] S4, installing the quartz tube with the flange in a vertical posture into the heater of a heating furnace, and the lowest position of the tellurium blocks in the quartz tube is not lower than and adjacent to the annular heating zone of the heater;
[0017] S5, the heating furnace runs a heating program, and the heating zone is heated from room temperature to a temperature higher than the melting point of tellurium but lower than the melting point of cadmium telluride, and is kept at a constant temperature, so that at least all the tellurium blocks inside the quartz tube are melted to form a molten zone of tellurium solvent;
[0018] S6, performing the first lift of the heater, so that the heating zone moves upward, and then the molten zone inside the quartz tube moves upward until the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube;
[0019] S7, performing the descent of the heater, so that the molten zone inside the quartz tube moves downward until the molten zone is at the bottom of the material inside the quartz tube;
[0020] S8, performing the second lift of the heater, so that the heating zone moves upward, and then the molten zone inside the quartz tube moves upward until the molten zone is at the top of the material inside the quartz tube;
[0021] S9, after the second lift of the heater ends, turn off the heating program, and take out the quartz tube after the furnace body of the heating furnace drops to room temperature;
[0022] S10, remove the flange and pour out the product. The top of the product is a tellurium solvent block, and below the tellurium solvent block is the purified cadmium telluride polycrystalline material, as Figure 2 shown;
[0023] S11. Separate the tellurium solvent block from the purified cadmium telluride polycrystalline material to obtain the purified cadmium telluride polycrystalline material.
[0024] S12. Sample and detect impurities in the purified cadmium telluride polycrystalline material.
[0025] In the cadmium telluride polycrystalline purification method according to the present disclosure, as Figure 1 shown, before the first lift of the heater in step S6, at least all the tellurium blocks in the quartz tube in step S5 are melted to form a molten zone of the tellurium solvent. During the first lift in step S6, as the heater is lifted, the cadmium telluride polycrystalline ingot above the molten zone will enter the heating zone of the heater and then continuously dissolve into the molten zone (i.e., the molten zone of the tellurium solvent) at the upper edge of the molten zone, and finally reach a saturated steady state in the molten zone. The lower edge of the molten zone will leave the heating zone of the heater, and then the temperature decreases. The cadmium telluride polycrystal is supersaturated in the tellurium solvent, so it precipitates at the low temperature in a dense microscopic layer unit of molecules or grains. The precipitated dense microscopic layer continuously stacks below the molten zone to form a dense cadmium telluride polycrystalline material, thereby realizing the upward movement of the molten zone and the preliminary purification of the cadmium telluride polycrystal. During the descent in step S7, as the heater descends, the cadmium telluride polycrystalline material below the molten zone will enter the heating zone of the heater and then continuously dissolve into the molten zone (i.e., the molten zone of the tellurium solvent) at the lower edge of the molten zone, and finally reach a saturated steady state in the molten zone. The upper edge of the molten zone will leave the heating zone of the heater, and then the temperature decreases. The cadmium telluride polycrystal is supersaturated in the tellurium solvent, so it precipitates at the low temperature (i.e., the upper edge) in a dense microscopic layer unit of molecules or grains. The precipitated dense microscopic layer continuously stacks above the molten zone to form a dense cadmium telluride polycrystalline material, thereby realizing the downward movement of the molten zone and the secondary purification of the cadmium telluride polycrystal. During the second lift in step S8, like the first lift process, the upward movement of the molten zone and the tertiary purification of the cadmium telluride polycrystal are realized. In step S2, the purity of the tellurium block is lower than that of the cadmium telluride polycrystalline ingot. Compared with the case where the purity of the tellurium block is not lower than that of the cadmium telluride polycrystalline ingot, the purity requirement of the tellurium block can be reduced, thereby reducing the material cost of the tellurium block. Thus, a tellurium block with low purity can be used as the solvent for the molten zone to perform the three purifications of lift - descent - lift as described above to obtain a cadmium telluride polycrystalline material with higher purity. In other words, through the cadmium telluride polycrystalline purification method of the present disclosure, the purity of the cadmium telluride polycrystal can be improved while reducing the cost, which is beneficial to improving the quality of the products prepared using the cadmium telluride polycrystal.
[0026] In step S1, the size of the quartz tube can be determined according to actual production. For example, in step S1, the inner diameter of the quartz tube is 70 mm and the length is 450 mm.
[0027] In one example, in step S1, the purity of the tellurium ingot is 5N; in step S2, the purity of the cadmium telluride polycrystalline ingot is 6N; in step S12, the purity of the purified cadmium telluride polycrystalline material reaches 7N.
[0028] In one example, in step S2, the mass ratio of cadmium telluride polycrystal to tellurium ingot is (2 - 3 kg):(0.8 - 1 kg).
[0029] In step S3, evacuate to below 5 Pa. In step S3, for example, the valve is a ball valve.
[0030] The installation of step S4 can be carried out by hoisting.
[0031] In one example, in step S5, the heating zone is heated from room temperature to 700 - 800 °C in 120 - 180 min and kept at a constant temperature for no less than 24 h.
[0032] In one example, in step S6, the heater is lifted upward at a speed of 2.5 - 3.5 mm / h. After the melting zone reaches the top of the material composed of tellurium and cadmium telluride in the quartz tube, the lifting of the heater stops and is maintained for no less than 6 h.
[0033] In one example, in step S7, the heater descends at a speed of 3 - 5 mm / h. After the melting zone reaches the bottom of the material composed of tellurium and cadmium telluride in the quartz tube, the descent of the heater stops and is maintained for no less than 6 h.
[0034] In one example, in step S8, the heater is lifted upward at a speed of 2.5 - 3.5 mm / h. After the melting zone reaches the top of the material composed of tellurium and cadmium telluride in the quartz tube, the lifting of the heater stops and is maintained for no less than 6 h.
[0035] Similarly, the removal of step S9 can be carried out by hoisting.
[0036] In one example, in step S11, hold the cadmium telluride polycrystalline material of the product and gently tap the tellurium solvent ingot with a tool to separate the tellurium solvent ingot from the purified cadmium telluride polycrystalline material. The tool can be an iron rod.
[0037] [Test]
[0038] Example 1
[0039] The cadmium telluride polycrystal purification method of Example 1 adopts the following steps:
[0040] S1, Load the tellurium ingot into the bottom of a vertical quartz tube. The inner diameter of the quartz tube is 70 mm, the length is 450 mm, the purity of the tellurium ingot is 5N, and the mass of the tellurium ingot is 800 g.
[0041] S2. Load a cadmium telluride polycrystalline ingot with a purity higher than that of the tellurium block into a quartz tube. The cadmium telluride polycrystalline ingot is located above the tellurium block. Among them, the purity of the cadmium telluride polycrystalline ingot is 6N, and the mass of the cadmium telluride polycrystalline ingot is 3 kg.
[0042] S3. Install a flange on the opening of the quartz tube, and use a vacuum pump to evacuate the inside of the quartz tube to 5 Pa through a connecting pipe on the flange. Then close the valve on the connecting pipe to maintain the vacuum inside the quartz tube. Among them, the valve is a ball valve.
[0043] S4. Use hoisting to install the quartz tube with the flange in a vertical position into the heater of the heating furnace. The lowest position of the tellurium block in the quartz tube is not lower than and adjacent to the annular heating zone of the heater.
[0044] S5. The heating furnace runs a heating program. The heating zone is heated from room temperature to 800 °C in 120 min and kept at a constant temperature for 24 h to melt at least all of the tellurium block inside the quartz tube to form a molten zone of tellurium solvent.
[0045] S6. Lift the heater for the first time at a speed of 3 mm / h to move the heating zone upward, and then move the molten zone inside the quartz tube upward until the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube. After the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube, stop lifting the heater and keep it for 6 h.
[0046] S7. Lower the heater at a speed of 5 mm / h to move the molten zone inside the quartz tube downward until the molten zone is at the bottom of the material inside the quartz tube. After the molten zone is at the bottom of the material composed of tellurium and cadmium telluride inside the quartz tube, stop lowering the heater and keep it for 6 h.
[0047] S8. Lift the heater for the second time at a speed of 3 mm / h to move the heating zone upward, and then move the molten zone inside the quartz tube upward until the molten zone is at the top of the material inside the quartz tube. After the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube, stop lifting the heater and keep it for 6 h.
[0048] S9. After the second lift of the heater is completed, turn off the heating program. After the furnace body of the heating furnace drops to room temperature, use hoisting to take out the quartz tube.
[0049] S10. Remove the flange and pour out the product. The top of the product is a tellurium solvent block, and below the tellurium solvent block is the purified cadmium telluride polycrystalline material.
[0050] S11. Hold the cadmium telluride polycrystalline material of the product and use an iron rod as a tool to gently tap the tellurium solvent block to separate the tellurium solvent block from the purified cadmium telluride polycrystalline material, and obtain the purified cadmium telluride polycrystalline material.
[0051] S12. Samples of the purified cadmium telluride polycrystalline material are taken for impurity detection. Among them, GDMS is used for impurity detection during sampling and detection.
[0052] Example 2
[0053] Except as follows, the rest is the same as in Example 1:
[0054] In step S6, the heater is lifted for the first time at a speed of 2.5 mm / h.
[0055] In step S7, the heater is lowered at a speed of 4 mm / h.
[0056] In step S8, the heater is lifted for the second time at a speed of 2.5 mm / h.
[0057] Comparative Example 1
[0058] The cadmium telluride polycrystalline purification method of Comparative Example 1 adopts the following steps:
[0059] Sa. Load the cadmium telluride polycrystalline ingot into the quartz tube. The purity of the cadmium telluride polycrystalline ingot is 6N, and the mass of the cadmium telluride polycrystalline ingot is 3 kg.
[0060] Sb. Install the flange on the opening of the quartz tube, and use a vacuum pump to evacuate the inside of the quartz tube to 5 Pa through the connecting pipe on the flange. Then close the valve on the connecting pipe to maintain the vacuum inside the quartz tube. Among them, the valve is a ball valve.
[0061] Sc. Use hoisting to install the quartz tube with the flange in a vertical posture into the heater of the heating furnace. The lowest position of the cadmium telluride polycrystalline ingot in the quartz tube is not lower than and adjacent to the annular heating zone of the heater.
[0062] Sd. The heating furnace runs the heating program. The heating zone is heated from room temperature to 1150 °C in 120 min and kept at a constant temperature for 24 h to form a molten zone in at least part of the cadmium telluride polycrystalline ingot in the quartz tube.
[0063] Se. Lift the heater at a speed of 30 mm / day to move the heating zone upward, and then move the molten zone in the quartz tube upward. On the third day when the heater moves, yellow smoke emerges from the furnace mouth of the heating furnace. Close the heating program. Wait for the heating furnace to cool to room temperature and take out the quartz tube, and it is confirmed that the quartz tube is broken.
[0064] Comparative Example 2
[0065] Except for not performing the lowering of the heater in step S7 and the second lifting of the heater in step S8 of Example 1 (that is, correspondingly, step S9 is carried out at the end of the first lifting in step S6), the rest is the same as in Example 1.
[0066] Comparative Example 3
[0067] Except that the purity of the tellurium block in step S1 is 6N, the rest is the same as in Example 1.
[0068] The purified cadmium telluride polycrystalline material in Example 1 was sampled to detect impurities. Except for tellurium (Te) and cadmium (Cd), the total content of all impurity elements was less than 100 ppb, and the purity of the purified cadmium telluride polycrystalline material reached 7N.
[0069] During the lifting process of the heater in Comparative Example 1, the quartz tube cracked, and the purification of the cadmium telluride polycrystalline ingot could not be achieved.
[0070] The purified cadmium telluride polycrystalline material in Comparative Example 2 was sampled to detect impurities. Except for tellurium (Te) and cadmium (Cd), the total content of all impurity elements was higher than 100 ppb, and the purity of the purified cadmium telluride polycrystalline material did not reach 7N. Figure 3 A cross-sectional photograph of the product of Comparative Example 2 (i.e., step S10) is shown.
[0071] The purified cadmium telluride polycrystalline material in Comparative Example 3 was sampled to detect impurities. Except for tellurium (Te) and cadmium (Cd), the total content of all impurity elements was less than 100 ppb, and the purity of the purified cadmium telluride polycrystalline material reached 7N. However, compared with Example 1, the purity of the tellurium block used in Comparative Example 3 was high, which was not conducive to reducing the cost of the tellurium block under the same purification purity.
[0072] Multiple exemplary embodiments are described using the detailed description above, 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 not shown for the sake of brevity.
Claims
1. A method for purifying cadmium telluride polycrystals, characterized in that, Including the steps: S1. Load tellurium blocks at the bottom of a vertically placed quartz tube. S2. Load cadmium telluride polycrystalline ingots with a purity higher than that of the tellurium blocks into the quartz tube, and the cadmium telluride polycrystalline ingots are located above the tellurium blocks. S3. Install a flange on the opening of the quartz tube, and use a vacuum pump to evacuate the inside of the quartz tube through a connecting pipe on the flange. Then close the valve on the connecting pipe to maintain the vacuum inside the quartz tube. S4. Install the quartz tube with the flange in a vertical position into the heater of the heating furnace. The lowest position of the tellurium blocks in the quartz tube is not lower than and adjacent to the annular heating zone of the heater. S5. The heating furnace runs a heating program. The heating zone is heated from room temperature to a temperature higher than the melting point of tellurium but lower than the melting point of cadmium telluride, and is kept at a constant temperature to make at least all the tellurium blocks in the quartz tube melt to form a molten zone of tellurium solvent. S6. Perform the first lift of the heater to move the heating zone upward, and then move the molten zone inside the quartz tube upward until the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube. S7. Perform the descent of the heater to move the molten zone inside the quartz tube downward until the molten zone is at the bottom of the material inside the quartz tube. S8. Perform the second lift of the heater to move the heating zone upward, and then move the molten zone inside the quartz tube upward until the molten zone is at the top of the material inside the quartz tube. S9. After the second lift of the heater ends, turn off the heating program. After the furnace body of the heating furnace drops to room temperature, take out the quartz tube. S10. Remove the flange and pour out the product. The top of the product is a tellurium solvent block and below the tellurium solvent block is the purified cadmium telluride polycrystalline material. S11. Separate the tellurium solvent block from the purified cadmium telluride polycrystalline material to obtain the purified cadmium telluride polycrystalline material. S12. Take a sample of the purified cadmium telluride polycrystalline material to detect impurities.
2. The cadmium telluride polycrystalline purification method according to claim 1, wherein In step S1, the inner diameter of the quartz tube is 70 mm and the length is 450 mm.
3. The cadmium telluride polycrystalline purification method according to claim 1, wherein In step S1, the purity of the tellurium blocks is 5N; In step S2, the purity of the cadmium telluride polycrystalline ingots is 6N; In step S12, the purity of the purified cadmium telluride polycrystalline material reaches 7N.
4. The cadmium telluride polycrystalline purification method according to claim 3, wherein In step S2, the mass ratio of cadmium telluride polycrystalline to tellurium blocks is (2 - 3 kg):(0.8 - 1 kg).
5. The cadmium telluride polycrystalline purification method according to claim 1, wherein In step S3, evacuate to below 5 Pa.
6. The cadmium telluride polycrystalline purification method according to claim 1, wherein In step S5, the heating zone is heated from room temperature to 700 - 800 °C in 120 - 180 min and kept at a constant temperature for not less than 24 h.
7. The cadmium telluride polycrystalline purification method according to claim 1, wherein In step S6, the heater is lifted upward at a speed of 2.5 - 3.5 mm / h. After the molten zone is at the top of the material composed of tellurium and cadmium telluride inside the quartz tube, the lift of the heater stops and is maintained for not less than 6 h.
8. The cadmium telluride polycrystal purification method according to claim 1, wherein in step S7, the heater descends at a speed of 3 - 5 mm / h. After the molten zone reaches the bottom of the material composed of tellurium and cadmium telluride in the quartz tube, the heater stops descending and remains for no less than 6 hours.
9. The cadmium telluride polycrystal purification method according to claim 1, wherein in step S8, the heater ascends at a speed of 2.5 - 3.5 mm / h. After the molten zone reaches the top of the material composed of tellurium and cadmium telluride in the quartz tube, the heater stops ascending and remains for no less than 6 hours.
10. The cadmium telluride polycrystal purification method according to claim 1, wherein in step S11, hold the cadmium telluride polycrystal material of the product by hand, and gently tap the tellurium solvent block with a tool to separate the tellurium solvent block from the purified cadmium telluride polycrystal material.