Method for removing selenium impurity in 4N tellurium powder and purifying 4N tellurium powder

Abstract

The invention discloses a method for removing selenium impurities in 4N tellurium powder and purifying the 4N tellurium powder, which comprises the following steps: carrying out smelting reaction on tellurium powder and sodium nitrate in an inert atmosphere, obtaining selenium-containing tellurium oxide and sodium nitrate residues by utilizing the characteristic that the molten sodium nitrate is specific to tellurium oxide, cleaning the product with ultrapure water, and removing sodium nitrate to obtain the 4N tellurium powder. After drying, tellurium oxide and selenium are subjected to vacuum distillation by utilizing the characteristic that the saturated vapor pressure of tellurium oxide is far lower than that of selenium, a tellurium dioxide material in the smelting crucible is taken and reacts with a reducing agent, and selenium-removed tellurium oxide can be obtained after reduction and drying. The method mainly aims at the problem that the impurity selenium is difficult to remove when tellurium is subjected to vacuum distillation, tellurium is converted into tellurium dioxide with a higher melting point, so that the elemental selenium is kept unchanged, the selenium can be directly removed by distillation, and meanwhile, a certain purification effect is also achieved.

Description

Technical Field

[0001] The invention belongs to the field of high-purity material purification, and in particular relates to a method for removing and purifying selenium impurities in 4N tellurium powder. Background Art

[0002] With the rapid development of the electronic information industry, the quality requirements for high-purity semiconductor materials are becoming increasingly higher. Tellurium is widely used in photovoltaic cells, infrared detectors and other fields due to its unique physical properties. For example, high-purity tellurium has broad prospects in the field of solar cells. It can be used to make high-efficiency photoelectric conversion elements; at the same time, high-purity tellurium compounds are also needed in the manufacturing process of infrared detectors and optoelectronic devices; in addition, in high-precision measurement equipment, such as superconducting quantum interference devices, extremely high requirements are also placed on the purity of tellurium. Whether in energy or information technology, high-quality tellurium plays an indispensable role.

[0003] However, since tellurium ore in nature usually contains a large amount of other elements, such as lead (Pb), antimony (Sb), selenium (Se), etc., it is necessary to go through a complex purification process to obtain high-purity tellurium products that meet application requirements. Selenium is one of the most difficult impurities in the tellurium refining process. It not only affects the conductivity and optical properties of the final product, but also increases the complexity and difficulty of the subsequent processing. In the preparation process of conventional high-purity tellurium, 4N tellurium is used as the raw material and is generally purified by processes such as vacuum distillation or zone melting. Although these methods can greatly improve the overall purity of tellurium and have a good purification effect on most impurity elements, the purification efficiency of selenium is low. This is mainly because, although the melting points of selenium and tellurium are quite different, the saturated vapor pressures of tellurium and selenium are relatively small above the melting point of tellurium; and the condensation temperature of tellurium is 270°C and the condensation temperature of selenium is 250°C. It is difficult to separate tellurium and selenium by segmented condensation, which makes it difficult to remove selenium by vacuum distillation of tellurium. At the same time, tellurium and selenium are complete solid solutions, and the distribution coefficient of selenium in tellurium is close to 1, so the efficiency of zone smelting for removing impurities from selenium is also very low. Usually, impurities in selenium can be removed by hydrogen reduction, but since hydrogen is dangerous, large-scale production should be avoided as much as possible.

[0004] In summary, although there are many mature purification technologies and impurity removal methods that have been successfully used in the industrial preparation of high-purity tellurium, in order to adapt to the growing market demand and continuously improving product quality standards, it is still necessary to develop more efficient and safe methods to remove selenium impurities in tellurium. Summary of the invention

[0005] The invention discloses a method for removing and purifying selenium impurities in 4N tellurium powder, so as to solve any of the above and other potential problems in the prior art.

[0006] To achieve the above object, the technical solution of the present invention is: a method for removing selenium impurities from 4N tellurium powder and purifying it, the method specifically comprising the following steps:

[0007] S1) placing 4N tellurium powder and sodium nitrate powder in a reaction vessel in a certain ratio, heating to a certain temperature under the protection of an inert gas, reacting for a period of time, washing the product with ultrapure water to remove the sodium nitrate, and drying to obtain tellurium dioxide powder containing selenium;

[0008] S2) distilling the tellurium dioxide powder obtained in S1) and then subjecting it to hydrogen reduction treatment to obtain high-purity tellurium.

[0009] Further, the specific process of S1) is:

[0010] S1.1) 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:0.5-3;

[0011] S1.2) Place the mixed powder into a cylindrical quartz crucible, place it in a pit-type atmosphere furnace, evacuate, introduce inert gas, heat to 310°C to 370°C, and react for 1 to 24 hours. After the reaction is completed, cool to room temperature with the furnace, and collect the mixture of tellurium dioxide powder and sodium nitrate;

[0012] S1.3) placing the mixture obtained in S1.2) in a quartz crucible, adding ultrapure water to pass through the mixture, and ultrasonically immersing the mixture for 10 min to 60 min to obtain a mixed solution, and then filtering and drying the mixed solution to obtain tellurium dioxide powder containing selenium impurities.

[0013] Furthermore, the inert gas includes nitrogen, argon and helium.

[0014] Further, the specific process of distillation in S2) is:

[0015] The tellurium dioxide powder containing selenium obtained in S1) is placed in a vacuum distillation furnace for vacuum distillation. The crucible used is an L-shaped quartz crucible. The heating temperature is 500-650°C and the vacuum degree is maintained at 1x10 -1 ~1x10 -3 Pa, distillation time is 4h~12h.

[0016] Furthermore, the L-shaped quartz crucible includes a vertical section and a horizontal section, and the horizontal section and the vertical section are connected by a quartz flange, and materials can be directly taken from the vertical section after disassembly; the vertical section is a heating zone, and the horizontal section is a condensation zone for impurities.

[0017] Furthermore, the length ratio of the horizontal section to the vertical section is 4-2:1, and the diameter ratio of the horizontal section to the vertical section is 1:1.5-3.

[0018] Furthermore, the specific process of hydrogen reduction in S2) is: heating reaction at 550°C to 600°C, at a hydrogen flow rate of 0.2 to 1 L / min, for 6 to 10 hours.

[0019] Furthermore, the method can obtain a tellurium ingot with a purity of not less than 99.9995% and a selenium mass percentage of not more than 0.000008%.

[0020] A high-purity tellurium is prepared by the above method.

[0021] The beneficial effect of the present invention is that due to the adoption of the above scheme, the method of the present invention converts tellurium into tellurium dioxide with a high melting point by a chemical method, while keeping selenium as elemental selenium, so that tellurium and selenium can form a large saturated vapor pressure difference during the vacuum distillation process, effectively avoiding the problem that selenium is difficult to remove during the traditional tellurium vacuum distillation process BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a process flow chart of a method for removing selenium impurities from 4N tellurium powder and purifying it. DETAILED DESCRIPTION

[0023] The implementation process of the present invention is further described below in conjunction with specific examples. It should be understood that these implementation processes are only used to further describe the present invention, rather than to limit the present invention. Based on the examples described in the present invention, various modifications made to the present invention by those skilled in the art without making creative work all belong to the protection scope of the present invention.

[0024] like Figure 1 As shown, the present invention provides a method for removing selenium impurities from 4N tellurium powder and purifying it, the method specifically comprising the following steps:

[0025] S1) placing 4N tellurium powder and sodium nitrate powder in a reaction vessel in a certain ratio, heating to a certain temperature under the protection of an inert gas, reacting for a period of time, washing the product with ultrapure water to remove the sodium nitrate, and drying to obtain tellurium dioxide powder containing selenium;

[0026] The specific process is:

[0027] S1.1) 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:0.5-3;

[0028] S1.2) Place the mixed powder into a cylindrical quartz crucible, place it in a pit-type atmosphere furnace, evacuate, introduce inert gas, heat to 310°C to 370°C, and react for 1 to 24 hours. After the reaction is completed, cool to room temperature with the furnace, and collect the mixture of tellurium dioxide powder and sodium nitrate;

[0029] S1.3) placing the mixture obtained in S1.2) in a quartz crucible, adding ultrapure water to pass through the mixture, and ultrasonically immersing the mixture for 10 min to 60 min to obtain a mixed solution, and then filtering and drying the mixed solution to obtain tellurium dioxide powder containing selenium impurities;

[0030] S2) distilling the tellurium dioxide powder obtained in S1), and then reducing it with hydrogen to obtain high-purity tellurium;

[0031] The specific process is:

[0032] The tellurium dioxide powder containing selenium obtained in S1) is placed in a vacuum distillation furnace for vacuum distillation. The crucible used is an L-shaped quartz crucible. The heating temperature is 500-650°C and the vacuum degree is maintained at 1x10 -1 ~1x10 -3 Pa, distillation time is 4h~12h.

[0033] The L-shaped quartz crucible includes a vertical section and a horizontal section, and the horizontal section and the vertical section are connected by a quartz flange, and materials can be directly taken from the vertical section after disassembly; the vertical section is a heating zone, and the horizontal section is a condensation zone for impurities.

[0034] The length ratio of the horizontal section to the vertical section is 4-2:1, and the diameter ratio of the horizontal section to the vertical section is 1:1.5-3.

[0035] The inert gas includes nitrogen, argon and helium.

[0036] The specific process of hydrogen reduction in S2) is: heating reaction at 550°C to 600°C, at a hydrogen flow rate of 0.2 to 1 L / min for 6 to 10 hours.

[0037] The purity of the tellurium ingot obtained by the method is not less than 99.9995%, and the mass percentage of selenium is not higher than 0.000008%.

[0038] A high-purity tellurium is prepared by the above method.

[0039] Example 1

[0040] First, 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:1, and the mixed powder is placed in a cylindrical quartz crucible. The adapted crucible is then placed in a pit-type atmosphere furnace, evacuated, and inert gas such as nitrogen, argon or helium is introduced. The reaction temperature is 320°C and the reaction time is 2 hours. After the reaction is completed, the furnace is cooled to room temperature. The mixture of tellurium dioxide powder and sodium nitrate is collected.

[0041] Then, in the process of washing with ultrapure water to remove sodium nitrate, the collected mixture of tellurium powder and sodium nitrate is placed in a quartz crucible, ultrapure water is added to pass through the mixture, and ultrasonic immersion is performed for 20 minutes to obtain a mixed solution, and then the mixed solution is filtered and dried to obtain tellurium dioxide powder containing selenium impurities.

[0042] The tellurium dioxide powder containing selenium impurities was placed in a vacuum distillation furnace for vacuum distillation. The crucible used was an L-shaped quartz crucible, the length ratio of the horizontal section to the vertical section was 3:1, and the diameter ratio of the horizontal section to the vertical section was 1:2. The heating temperature was 600°C, and the vacuum degree was maintained at 1x10 -3 Pa, the distillation time is 4h. After completion, the tellurium dioxide is reduced at 580°C for 10h in a hydrogen atmosphere. The purity of the tellurium ingot finally prepared is 99.9995%, and the mass percentage of selenium is 0.000008%.

[0043] Example 2

[0044] First, 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:2, and the mixed powder is placed in a cylindrical quartz crucible. The adapted crucible is then placed in a pit-type atmosphere furnace, evacuated, and inert gas such as nitrogen, argon or helium is introduced. The reaction temperature is 320°C and the reaction time is 4 hours. After the reaction is completed, the furnace is cooled to room temperature. The mixture of tellurium dioxide powder and sodium nitrate is collected.

[0045] Then, in the process of washing with ultrapure water to remove sodium nitrate, the collected mixture of tellurium powder and sodium nitrate is placed in a quartz crucible, ultrapure water is added to pass through the mixture, and ultrasonic immersion is performed for 40 minutes to obtain a mixed solution, and then the mixed solution is filtered and dried to obtain tellurium dioxide powder containing selenium impurities.

[0046] The tellurium dioxide powder containing selenium impurities was placed in a vacuum distillation furnace for vacuum distillation. The crucible used was an L-shaped quartz crucible, the length ratio of the horizontal section to the vertical section was 3:1, and the diameter ratio of the horizontal section to the vertical section was 1:2. The heating temperature was 620°C, and the vacuum degree was maintained at 1x10 -3 Pa, the distillation time is 8h. After completion, the tellurium dioxide is reduced at 580°C for 10h in a hydrogen atmosphere. The purity of the finally prepared tellurium ingot is 99.9996%, and the mass percentage of selenium is 0.000005%.

[0047] Example 3

[0048] First, 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:3, and the mixed powder is placed in a cylindrical quartz crucible. The adapted crucible is then placed in a pit-type atmosphere furnace, evacuated, and inert gas such as nitrogen, argon or helium is introduced. The reaction temperature is 320°C and the reaction time is 6 hours. After the reaction is completed, the furnace is cooled to room temperature. The mixture of tellurium dioxide powder and sodium nitrate is collected.

[0049] Then, in the process of washing with ultrapure water to remove sodium nitrate, the collected mixture of tellurium powder and sodium nitrate is placed in a quartz crucible, ultrapure water is added to pass through the mixture, and ultrasonic immersion is performed for 60 minutes to obtain a mixed solution, and then the mixed solution is filtered and dried to obtain tellurium dioxide powder containing selenium impurities.

[0050] The tellurium dioxide powder containing selenium impurities was placed in a vacuum distillation furnace for vacuum distillation. The crucible used was an L-shaped quartz crucible with a horizontal section and a vertical section length ratio of 3:1 and a horizontal section and a vertical section diameter ratio of 1:2. The heating temperature was 650°C and the vacuum degree was maintained at 1x10 -3 Pa, the distillation time is 12h. After completion, the tellurium dioxide is reduced at 580°C for 10h in a hydrogen atmosphere. The purity of the finally prepared tellurium ingot is 99.9998%, and the mass percentage of selenium is 0.000003%.

[0051] Comparative Example

[0052] 4N tellurium powder was placed in a vacuum distillation furnace for vacuum distillation. The heating temperature was 600°C and the vacuum degree was maintained at 1x10 -3 Pa, the distillation time is 12h. The purity of the finally prepared tellurium is 99.9992%, and the mass percentage of selenium is 0.0001%.

[0053] The above is a detailed introduction to a method for removing selenium impurities from 4N tellurium powder and purifying it provided in the embodiment of the present application. The description of the above embodiment is only used to help understand the method and its core idea of ​​the present application; at the same time, for those skilled in the art, according to the idea of ​​the present application, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as limiting the present application.

[0054] For example, certain words are used in the specification and claims to refer to specific components. Those skilled in the art should understand that hardware manufacturers may use different nouns to refer to the same component. This specification and claims do not use differences in names as a way to distinguish components, but use differences in the functions of components as the criteria for distinction. As mentioned throughout the specification and claims, "including" and "comprising" are open-ended terms, so they should be interpreted as "including / including but not limited to". "Approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and basically achieve the technical effect. The subsequent description of the specification is a preferred embodiment of the present application, but the description is for the purpose of illustrating the general principles of the present application, and is not used to limit the scope of the present application. The scope of protection of the present application shall be subject to that defined in the attached claims.

[0055] It should also be noted that the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a product or system including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such a product or system. In the absence of more restrictions, the elements defined by the sentence "comprises a ..." do not exclude the existence of other identical elements in the product or system including the elements.

[0056] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0057] The above description shows and describes several preferred embodiments of the present application, but as mentioned above, it should be understood that the present application is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the application concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art do not deviate from the spirit and scope of the present application, and should be within the scope of protection of the claims attached to the present application.

Claims

1. A method for removing selenium impurities from 4N tellurium powder and purifying it, characterized in that: The method specifically comprises the following steps: S1) placing 4N tellurium powder and sodium nitrate powder in a reaction vessel in a certain ratio, heating to a certain temperature under the protection of an inert gas, reacting for a period of time, washing the product with ultrapure water to remove the sodium nitrate, and drying to obtain tellurium dioxide powder containing selenium; S2) distilling the tellurium dioxide powder obtained in S1) and then subjecting it to hydrogen reduction treatment to obtain high-purity tellurium.

2. The method according to claim 1, characterized in that The specific process of S1) is: S1.1) 4N tellurium powder and sodium nitrate powder are fully mixed in a mass ratio of 1:0.5-3; S1.2) Place the mixed powder into a cylindrical quartz crucible, place it in a pit-type atmosphere furnace, evacuate, introduce inert gas, heat to 310°C to 370°C, and react for 1 to 24 hours. After the reaction is completed, cool to room temperature with the furnace, and collect the mixture of tellurium dioxide powder and sodium nitrate; S1.3) placing the mixture obtained in S1.2) in a quartz crucible, adding ultrapure water to pass through the mixture, and ultrasonically immersing the mixture for 10 min to 60 min to obtain a mixed solution, and then filtering and drying the mixed solution to obtain tellurium dioxide powder containing selenium impurities.

3. The method according to claim 2, characterized in that The inert gas includes nitrogen, argon and helium.

4. The method according to claim 1, characterized in that: The specific process of distillation in S2) is: The tellurium dioxide powder containing selenium obtained in S1) is placed in a vacuum distillation furnace for vacuum distillation. The crucible used is an L-shaped quartz crucible. The heating temperature is 500-650°C and the vacuum degree is maintained at 1x10 -1 ~1x10 -3 Pa, distillation time is 4h~12h.

5. The method according to claim 4, characterized in that The L-shaped quartz crucible includes a vertical section and a horizontal section, and the horizontal section and the vertical section are connected by a quartz flange, and materials can be directly taken from the vertical section after disassembly; the vertical section is a heating zone, and the horizontal section is a condensation zone for impurities.

6. The method according to claim 5, characterized in that The length ratio of the horizontal section to the vertical section is 4-2:1, and the diameter ratio of the horizontal section to the vertical section is 1:1.5-3.

7. The method according to claim 1, characterized in that The specific process of hydrogen reduction in S2) is: heating reaction at 550°C to 600°C, at a hydrogen flow rate of 0.2 to 1 L / min for 6 to 10 hours.

8. The method according to claim 1, characterized in that: The purity of the tellurium ingot obtained by the method is not less than 99.9995%, and the mass percentage of selenium is not higher than 0.000008%.

9. A high-purity tellurium, characterized in that: The high-purity tellurium is prepared by the method according to any one of claims 1 to 8.

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