High-purity bismuth antimonide and preparation method thereof

Abstract

The invention belongs to the technical field of new materials, and discloses a preparation method of high-purity bismuth antimonide, which comprises the following steps: sealing an antimony elementary substance and a bismuth elementary substance in a vacuumized container, and heating for melting reaction to prepare the high-purity bismuth antimonide, the molar ratio of the antimony elementary substance to the bismuth elementary substance is 1: 1; the heating and melting are carried out in two steps: firstly heating to a first temperature and reacting for a period of time, then heating to a second temperature and reacting for a period of time, and keeping the container in a shaking state at the second temperature stage; the first temperature is higher than the melting point temperature of bismuth and lower than the melting point temperature of antimony; the second temperature is higher than the melting point temperature of antimony. The reaction is carried out through two-stage heating, the reaction temperature is controlled to be below the melting point temperature of antimony, antimony volatilization is avoided, after most of the reaction is completely carried out, heating is carried out, the reaction is thoroughly carried out, the vapor pressure in the vacuum cavity is reduced, antimony loss is avoided, and therefore the product purity can be effectively improved. Meanwhile, the invention further provides the high-purity bismuth antimonide prepared on the basis of the method.

Description

Technical Field

[0001] The present invention relates to the field of new materials, and in particular to high-purity bismuth antimonide and a preparation method thereof. Background Art

[0002] Bismuth antimonide is mostly prepared by melting method. The disadvantage of melting method is that the saturated vapor pressure of antimony is relatively large, which leads to the problem of impure product if antimony and bismuth are mixed according to the molar ratio of 1:1. According to relevant records, at 630℃ (the melting point of antimony), the saturated vapor pressure is 18.67Pa. When the temperature rises to 700℃, the saturated vapor pressure rises sharply to 58.26Pa. When the temperature rises to 800℃, the saturated vapor pressure further rises to 221Pa.

[0003] In vacuum melting, the melting temperature cannot be just the melting temperature of antimony. In order to make the material react more completely, the temperature is generally raised to 30°C above the melting temperature, generally reaching 700°C to fully mix the materials and improve the uniformity of the reaction. In this case, the vapor of antimony will fill the cavity, resulting in impure products.

[0004] Therefore, in the prior art, there is a difficult problem to solve: antimony will inevitably volatilize at the smelting temperature, and in order to fully react, the temperature must reach above the melting point of antimony.

[0005] In the prior art, CN106216872A discloses a SnBiSb low-temperature lead-free solder and a preparation method thereof, which discloses in the specification: the preparation method of the Bi-Sb master alloy comprises the following steps: adding Bi and Sb with a purity of 99.99wt.% into a vacuum melting furnace according to a certain alloy ratio, and vacuumizing to 1×10 -2 -×10 -1 Pa, filled with nitrogen, heated to 650-700°C for melting, and electromagnetically stirred to make the alloy composition uniform, and vacuum cast to prepare BiSb master alloy;

[0006] After analysis, we believe that the above method for preparing high-purity bismuth antimonide still has the problems mentioned above.

[0007] The technical problem solved in this case is how to improve the purity of bismuth antimonide. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing high-purity bismuth antimonide. The present invention performs a reaction by a solid solution method, controls the reaction temperature below the melting point of antimony, avoids antimony volatilization, and after most of the reaction is completed, raises the temperature to react thoroughly to reduce the vapor pressure in the vacuum chamber and avoid antimony loss, thereby effectively improving the purity of the product.

[0009] At the same time, the present invention also provides high-purity bismuth antimonide prepared based on the method.

[0010] To achieve the above objectives, this application discloses:

[0011] A method for preparing high-purity bismuth antimonide, characterized in that antimony and bismuth are sealed in a vacuum container and heated to melt and react to prepare high-purity bismuth antimonide;

[0012] The molar ratio of the antimony element to the bismuth element is 1:1;

[0013] The heating and melting is carried out in two steps: first heating to a first temperature, reacting for a period of time, and then heating to a second temperature, reacting for a period of time, and at the second temperature stage, keeping the container in a shaking state;

[0014] The first temperature is higher than the melting point of bismuth and lower than the melting point of antimony; the second temperature is higher than the melting point of antimony.

[0015] At the first temperature of the present invention, bismuth melts, and antimony enters into the bismuth metal liquid in the form of solid solution to react. At this stage, most of the reaction between bismuth and antimony has been carried out, and a small amount of antimony and bismuth elements exist in the system; then the temperature is increased, and during the temperature increase process, the remaining elements continue to react. When the second temperature is reached, there are very few elements remaining in the system. At this stage, the container is kept warm and shaken to fully mix the materials and improve the uniformity and thoroughness of the reaction.

[0016] Through the method of the present invention, the purity of the product of the present invention reaches a high purity level.

[0017] In the above method for preparing high-purity bismuth antimonide, the first temperature is at least 20° C. higher than the melting point of bismuth; and the second temperature is at least 50° C. higher than the melting point of antimony.

[0018] More preferably, the first temperature is 300-400°C; the second temperature is 700-750°C.

[0019] The first temperature is used to ensure that bismuth is fully melted so that antimony can be solid-dissolved. Therefore, the minimum temperature is recommended to be at least 20°C higher than the melting point of bismuth. The second temperature is the melting temperature of antimony. Controlling this temperature can allow the reaction to proceed thoroughly.

[0020] In the above-mentioned method for preparing high-purity bismuth antimonide, the container is a quartz tube with an inner wall coated with a carbon film.

[0021] In the above-mentioned method for preparing high-purity bismuth antimonide, after the antimony element and bismuth element are filled into the quartz tube, they occupy 25-50% of the volume of the quartz tube.

[0022] Filling degree is an effective way to improve purity. If the filling degree is too low, such as 10% or 1%, it means that there is more space to accommodate steam. If the filling degree is too high, the melt cannot be fully mixed in the later swinging; both situations will result in the purity cannot be further improved.

[0023] In the above-mentioned method for preparing high-purity bismuth antimonide, the antimony element and bismuth element are filled into a quartz tube in the form of particles, blocks or powders.

[0024] In the present invention, small pieces of 0.5 to 2 cm are used as raw materials for preparation. When bismuth is melted, the antimony block can be slowly dissolved into the melt, so that the reaction proceeds smoothly until all the antimony blocks disappear. In addition, this block processing method reduces the difficulty of pre-treatment, and does not require ball making and grinding.

[0025] In the above method for preparing high-purity bismuth antimonide, in the second temperature stage, the quartz tube is swung at an angle of 45 to 60 degrees.

[0026] This is one of the advantages of using quartz tubes. The tubular body is easy to swing, which is conducive to equipment operation.

[0027] In the above-mentioned method for preparing high-purity bismuth antimonide, the first temperature is maintained at a constant temperature for 1 to 2 hours; the second temperature is maintained at a constant temperature for 2 to 4 hours. Of course, the present invention does not strictly limit the time of the two temperature stages. In actual production, a longer time is also feasible. The above temperature range is proposed based on production efficiency and cost considerations.

[0028] In the above-mentioned method for preparing high-purity bismuth antimonide, the temperature is raised from room temperature to the first temperature at a heating rate of 5 to 10°C / min, and the temperature is raised from the first temperature to the second temperature at a rate of 3 to 6°C / min. The heating rate of the second temperature should be controlled to be slower than that of the previous stage, so that the residual element has sufficient time to continue to react completely and reduce the impurity content in the melt when the highest temperature is reached.

[0029] At the same time, the present invention also discloses a high-purity bismuth antimonide, which is prepared by any of the above methods.

[0030] This application has at least the following beneficial effects:

[0031] The present invention uses a solid solution method to carry out the reaction, so that the reaction temperature is controlled below the melting point of antimony to avoid antimony volatilization. After most of the reactions are completed, the temperature is raised to react completely to reduce the vapor pressure in the vacuum chamber and avoid antimony loss, thereby effectively improving the purity of the product. DETAILED DESCRIPTION

[0032] The present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. In the description of the present invention, it should be noted that, if no specific conditions are specified in the embodiments, the conditions are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0033] Example 1

[0034] 1. High-purity bismuth blocks and antimony blocks are loaded into a quartz tube coated with a carbon film in a molar ratio of 1:1. The height of the filler is 30% of the height of the quartz tube; the size of the bismuth block and the antimony block is between 0.5 and 2 cm (the subsequent examples are all of this specification).

[0035] 2. Evacuate the quartz tube until the vacuum degree is 1×10 -2 Seal the tube after Pa.

[0036] 3. Place the sealed quartz tube in a heating furnace, heat it at a rate of 6°C / min; keep it at 300°C for 2 hours; keep it at 700°C for 4 hours at a rate of 3°C / min.

[0037] 4. When the temperature reaches the highest temperature, start to swing vertically 60° left and right.

[0038] 5. Cooling down. When the furnace chamber temperature drops to room temperature, discharge the material to obtain bismuth antimonide.

[0039] Example 2

[0040] 1. Load high-purity bismuth blocks and antimony blocks in a molar ratio of 1:1 into a quartz tube coated with a carbon film, and the height of the filling is 25% of the height of the quartz tube.

[0041] 2. Evacuate the quartz tube until the vacuum degree is 1×10 -3 Seal the tube after Pa.

[0042] 3. Place the sealed quartz tube in a heating furnace, heat it at a rate of 5°C / min; keep it at 400°C for 1 hour; keep it at 6°C / min; keep it at 750°C for 2 hours.

[0043] 4. When the temperature reaches the highest temperature, start to swing vertically 50° left and right.

[0044] 5. Cooling down. When the furnace chamber temperature drops to room temperature, discharge the material to obtain bismuth antimonide.

[0045] Example 3

[0046] 1. Load high-purity bismuth blocks and antimony blocks in a molar ratio of 1:1 into a quartz tube coated with a carbon film, and the height of the filling is 50% of the height of the quartz tube.

[0047] 2. Evacuate the quartz tube until the vacuum degree is 1×10-3 Seal the tube after Pa.

[0048] 3. Place the sealed quartz tube in a heating furnace, heat it at a rate of 10°C / min; keep it at 350°C for 2 hours; and keep it at 720°C for 3 hours at a rate of 5°C / min.

[0049] 4. When the temperature reaches the highest temperature, start to swing vertically 45° left and right.

[0050] 5. Cooling down. When the furnace chamber temperature drops to room temperature, discharge the material to obtain bismuth antimonide.

[0051] Comparative Example 1

[0052] 1. Load high-purity bismuth and antimony blocks into a carbon-film-coated quartz tube in a molar ratio of 1:1. The height of the filler is 30% of the height of the quartz tube.

[0053] 2. Evacuate the quartz tube until the vacuum degree is 1×10 -2 Seal the tube after Pa.

[0054] 3. Place the sealed quartz tube in a heating furnace, raise the temperature at a rate of 6°C / min, and keep it at a constant temperature of 700°C for 6 hours.

[0055] 4. When the temperature reaches the highest temperature, start to swing vertically 60° left and right.

[0056] 5. Cooling down. When the furnace chamber temperature drops to room temperature, discharge the material to obtain bismuth antimonide.

[0057] Comparative Example 2

[0058] 1. Load high-purity bismuth and antimony blocks into a carbon-film-coated quartz tube in a molar ratio of 1:1. The height of the filler is 30% of the height of the quartz tube.

[0059] 2. Evacuate the quartz tube until the vacuum degree is 1×10 -2 Seal the tube after Pa.

[0060] 3. Place the sealed quartz tube in a heating furnace and heat it at a rate of 6°C / min; keep it at 300°C for 6 hours.

[0061] 4. When the temperature reaches the highest temperature, start to swing vertically 60° left and right.

[0062] 5. Cooling down. When the furnace chamber temperature drops to room temperature, discharge the material to obtain bismuth antimonide.

[0063] Comparative Example 3

[0064] The method is generally the same as Example 1, except that the device is left to stand at the highest temperature without turning on the shaking.

[0065] Performance Testing

[0066] The test item is product purity, and the content of elemental antimony and elemental bismuth is tested by DSC method;

[0067] Table 1 Test results

[0068] Case Antimony ppm Bismuth ppm Example 1 ＜300 ＜300 Example 2 ＜300 ＜300 Example 3 ＜300 ＜300 Comparative Example 1 ＜300 590 Comparative Example 2 1954 2078 Comparative Example 3 ＜300 465

[0069] Result analysis:

[0070] 1. It can be seen from Examples 1 to 3 that, by adopting the method of the present invention, antimony can enter the melt in the form of solid solution to react, and continue to react after heating to the second temperature, so that the obtained product has high purity and low free matter content.

[0071] 2. It can be seen from Comparative Example 1 that if the reaction temperature is increased to 700°C, the residual bismuth will increase and the residual antimony will be less, because during the cooling process, the antimony in the atmosphere will cool to the surface of the melt, and during the detection process, the core of the product is sampled, so there will be more bismuth and less antimony.

[0072] 3. It can be seen from Comparative Example 2 that if the reaction temperature is controlled below the melting point of bismuth, the reaction uniformity will be poor, resulting in a significant increase in bismuth and antimony residues.

[0073] 4. Comparative Example 3 shows that in the absence of the second temperature swing mixing, the system uniformity is poor, resulting in a slight increase in bismuth and antimony residues.

[0074] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be considered exemplary and non-restrictive in all respects, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention.

Claims

1. A method for preparing high-purity bismuth antimonide, characterized in that: The antimony element and the bismuth element are sealed in a vacuum container and heated to melt and react to prepare high-purity bismuth antimonide; The molar ratio of the antimony element to the bismuth element is 1:1; The heating and melting is carried out in two steps: first heating to a first temperature, reacting for a period of time, and then heating to a second temperature, reacting for a period of time, and at the second temperature stage, keeping the container in a shaking state; The first temperature is higher than the melting point of bismuth and lower than the melting point of antimony; the second temperature is higher than the melting point of antimony.

2. The method for preparing high-purity bismuth antimonide according to claim 1, characterized in that: The first temperature is at least 20° C. higher than the melting point of bismuth; the second temperature is at least 50° C. higher than the melting point of antimony.

3. The method for preparing high-purity bismuth antimonide according to claim 2, characterized in that: The first temperature is 300-400°C; the second temperature is 700-750°C.

4. The method for preparing high-purity bismuth antimonide according to claim 1, characterized in that: The container is a quartz tube with a carbon film coated on the inner wall.

5. The method for preparing high-purity bismuth antimonide according to claim 4, characterized in that: After the antimony element and the bismuth element are filled into the quartz tube, they occupy 25-50% of the volume of the quartz tube.

6. The method for preparing high-purity bismuth antimonide according to claim 4, characterized in that: The antimony element and the bismuth element are filled into a quartz tube in the form of particles, blocks or powders.

7. The method for preparing high-purity bismuth antimonide according to claim 4, characterized in that: In the second temperature stage, the quartz tube is swung at an angle of 45 to 60 degrees.

8. The method for preparing high-purity bismuth antimonide according to claim 1, characterized in that: The first temperature is maintained at a constant temperature for 1 to 2 hours; the second temperature is maintained at a constant temperature for 2 to 4 hours.

9. The method for preparing high-purity bismuth antimonide according to claim 8, characterized in that: The temperature is raised from room temperature to the first temperature at a rate of 5 to 10°C / min, and the temperature is raised from the first temperature to the second temperature at a rate of 3 to 6°C / min.

10. A high-purity bismuth antimonide, characterized in that: The method is prepared by any one of claims 1 to 9.