Antimony tritelluride and preparation method thereof

Abstract

The present application relates to the field of chemical production technology, and discloses a method for preparing antimony tritelluride, comprising the following steps: step 1: mixing Te powder and Sb powder to obtain a mixed material; step 2: placing the mixed material in an inert gas environment; step 3: heating the mixed material in sections; step 4: cooling the mixed material to obtain a finished antimony tritelluride; in step 3, the sectioned heating includes primary heating and secondary heating, and the primary heating is specifically: heating to 350-400°C at a heating rate of 5-10°C / min, keeping the temperature for 30-45min, and obtaining a primary heating product; the secondary heating is specifically: heating the primary heating product to 500-580°C, keeping the temperature for 60-90min, and obtaining a secondary heating product; and a reducing gas is continuously introduced during the heating process. Through this design, the oxygen content of the prepared antimony tritelluride is greatly reduced, and the purity of the antimony tritelluride is improved. In addition, the present application also discloses an antimony tritelluride.

Description

Technical Field

[0001] The present application relates to the field of chemical production technology, and in particular to antimony tritelluride and a preparation method thereof. Background Art

[0002] As energy crisis and environmental pollution become increasingly prominent, thermoelectric technology, as one of the clean energy technologies, has rapidly attracted widespread attention in the field of waste heat power generation and refrigeration. The direct mutual conversion between thermal energy and electrical energy is achieved by using the principle of directional movement of carriers in the temperature field and electric field inside the semiconductor, which is the so-called semiconductor temperature difference power generation and refrigeration technology. Compared with traditional power generation and refrigeration equipment, thermoelectric related equipment has the advantages of modular structure, stable performance, long service life, safe operation, no noise, and no pollutant emissions. The modular structural characteristics of thermoelectric devices make it easy to utilize some energy sources (such as solar energy, nuclear energy, and waste heat emitted by industry or transportation) to form corresponding power generation equipment or combine them into a combined power generation system. Therefore, thermoelectric technology has a broad application space in many fields and can play a certain role in improving the comprehensive utilization efficiency of energy in the entire social system. Tellurium antimony compounds, as an important type of thermoelectric material, have attracted much attention in recent years.

[0003] Chinese patent 201510143622.4 discloses a method for rapidly preparing antimony telluride thermoelectric materials, which mainly includes the following steps:

[0004] 1) According to Sb 2 Te 3 Weigh Sb powder and Te powder according to the stoichiometric ratio of each element, and then grind and mix them evenly to obtain a mixed material;

[0005] 2) The mixed material obtained in step 1) is subjected to spark plasma activation sintering and naturally cooled to obtain the antimony telluride thermoelectric material; the spark plasma activation sintering process is: first, under the condition of vacuum degree less than 10Pa and no sintering pressure, the mixture is heated to 380-410°C at a heating rate of 60-80°C / min, kept warm for 10-15min, then pressurized to 30-40MPa, and continued to be kept warm for 5-10min.

[0006] This scheme involves first heating the mixed material to near the melting point of tellurium at a heating rate of 60-80°C / min, and keeping it warm for 10-15 minutes, then pressurizing it to 30-40MPa, and continuing to keep warm and sinter for 5-10 minutes, to finally obtain antimony telluride thermoelectric material. This method has a short preparation cycle, low energy consumption, good repeatability, and is suitable for large-scale production.

[0007] The problem to be solved in this application is: how to develop a method for preparing antimony tritelluride that has the advantages of large-scale production and high purity. Summary of the invention

[0008] The purpose of the present application is to provide a method for preparing antimony tritelluride. The method reduces the occurrence of free tellurium during the reaction by heating twice, and uses excess tellurium for the reaction to prevent incomplete reaction of antimony during the reaction. In the heating process, the heating rate is reduced, and the hydrogen environment is used to reduce the oxygen content in the product, thereby improving the purity of the product antimony tritelluride. At the same time, the operation steps of the present application are simple, the energy consumption is low, the repeatability is good, and it is suitable for large-scale production.

[0009] A method for preparing antimony tritelluride comprises the following steps:

[0010] Step 1: Mix Te powder and Sb powder to obtain a mixed material;

[0011] Step 2: Place the mixed material in an inert gas environment;

[0012] Step 3: heating the mixed material in sections;

[0013] Step 4: Cooling the mixed material to obtain antimony tritelluride finished product;

[0014] In step 3, the segmented heating includes primary heating and secondary heating, wherein the primary heating is specifically: heating to 350-400° C. at a heating rate of 5-10° C. / min, and keeping the temperature for 30-45 min to obtain a primary heating product;

[0015] The secondary heating is specifically as follows: heating the primary heating product to 500-580°C at a heating rate of 5-10°C / min, and keeping the temperature for 60-90min to obtain a secondary heating product;

[0016] And during the temperature rising process of step 3, the reducing agent is continuously introduced, and the flow rate of the reducing agent is 4-10 L / min.

[0017] Preferably, the reducing gas includes but is not limited to hydrogen, carbon monoxide, hydrogen sulfide, methane, and sulfur monoxide.

[0018] Preferably, step 1 specifically comprises: weighing Te powder and Sb powder according to a molar ratio of Te to Sb of 3.05 to 3.10:2, and mixing them uniformly in an inert gas atmosphere to obtain a mixed material.

[0019] More preferably, the molar ratio of Te to Sb includes but is not limited to 3.05:2, 3.06:2, 3.07:2, 3.08:2, 3.09:2, 3.10:2.

[0020] Preferably, step 2 is specifically as follows: placing the mixed material prepared in step 1 in a graphite boat, and placing it in a tubular atmosphere furnace, while opening the air inlet and air outlet of the tubular atmosphere furnace, and continuously introducing inert gas, wherein the volume of the inert gas introduced is 2 to 3 times the volume of the tubular atmosphere furnace.

[0021] It should be explained and understood that in step 2, the purpose of introducing inert gas into the tubular atmosphere furnace is to exhaust the air in the tubular atmosphere furnace. Therefore, technicians in this field can choose the volume of the inert gas introduced according to actual conditions. The present application does not impose too many restrictions on the volume of the inert gas introduced into the tubular atmosphere furnace. However, under the condition that the purpose of exhausting air can be achieved, for the purpose of saving energy, the present application recommends that the volume of the inert gas introduced be 2 to 3 times the volume of the tubular atmosphere furnace.

[0022] Preferably, step 3 is specifically as follows: turning on the heating mode of the tubular atmosphere furnace, heating the temperature to 350-400° C. at a heating rate of 5-10° C. / min, keeping the temperature for 30-45 min, then heating the temperature to 500-580° C., keeping the temperature for 60-90 min;

[0023] During the heating process of step 3, reducing gas is continuously introduced, and the flow rate of the reducing gas is 4-6 L / min;

[0024] Considering the safety during use, it is more recommended to use non-toxic hydrogen to reduce the oxygen content. Therefore, more preferably, in step 3, the temperature is increased to 360-390°C at a heating rate of 6-9°C / min, kept warm for 30-45min, then increased to 520-570°C, kept warm for 60-90min, and hydrogen is continuously introduced during the heating process of step 3, and the flow rate of hydrogen is 4-6L / min;

[0025] More preferably, in step 3, the heating rate includes but is not limited to 6°C / min, 6.5°C / min, 7°C / min, 7.5°C / min, 8°C / min, 8.5°C / min, 9°C / min;

[0026] It should be explained and understood that in step 2, the purpose of introducing hydrogen into the tubular atmosphere furnace is to reduce the oxidized tellurium powder and antimony powder, so as to reduce the oxygen content of the tellurium powder and antimony powder and improve the purity of the tellurium powder and antimony powder. Therefore, technicians in this field can choose the flow rate of the hydrogen introduced according to actual conditions. The present application does not impose too many restrictions on the flow rate of the hydrogen introduced into the tubular atmosphere furnace. However, if the above-mentioned purpose can be achieved, for the purpose of saving energy, the present application recommends that the flow rate of the hydrogen introduced be 4-6L / min.

[0027] Preferably, step 4 specifically comprises: introducing an inert gas into the tubular atmosphere furnace and exhausting the reducing gas in the tubular atmosphere furnace, cooling to room temperature, taking out the material, and obtaining antimony tritelluride.

[0028] Preferably, in step 1, the molar ratio of Te to Sb is 3.06-3.08:2.

[0029] In addition, the present application also discloses antimony tritelluride, which is prepared by the above-mentioned method for preparing antimony tritelluride.

[0030] The beneficial effects of this application are:

[0031] The purpose of the present application is to provide a method for preparing antimony tritelluride. The method reduces the occurrence of free tellurium during the reaction by heating twice, and uses excess tellurium for the reaction to prevent incomplete reaction of antimony during the reaction. In the heating process, the heating rate is reduced, and the hydrogen environment is used to reduce the oxygen content in the reactants, thereby improving the purity of the product antimony tritelluride. At the same time, the operating steps of the present application are simple, the energy consumption is low, the repeatability is good, and it is suitable for large-scale production. DETAILED DESCRIPTION

[0032] The present application will be described clearly and completely below in conjunction with the examples of the present application. In the description of the present application, it should be noted that if the specific conditions are not specified in the examples, they 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] Step 1: Weigh Te powder and Sb powder according to the molar ratio of Te to Sb being 3.05:2, mix them evenly in an argon atmosphere to obtain a mixed material.

[0035] Step 2: Place the mixed powder in a graphite boat and put it into a tubular atmosphere furnace, the inlet and outlet of which are both open, and introduce argon gas into the tubular atmosphere furnace, the volume of which is 3 times the volume of the tubular atmosphere furnace.

[0036] Step 3: Turn on the heating mode of the tubular atmosphere furnace, heat up to 350°C at a heating rate of 8°C / min, keep warm for 45 minutes, then heat up to 550°C at a heating rate of 8°C / min, keep warm for 80 minutes. Only during the heating process, introduce hydrogen into the tubular atmosphere furnace at a hydrogen flow rate of 8L / min.

[0037] Step 4: Subsequently, the heating is stopped and argon gas is introduced into the tubular atmosphere furnace. After cooling to room temperature, the material is taken out to obtain the finished product of antimony tritelluride.

[0038] Example 2

[0039] Step 1: Weigh Te powder and Sb powder according to a molar ratio of Te to Sb of 3.1:2, mix them evenly in a helium atmosphere to obtain a mixed material.

[0040] Step 2: Place the mixed powder in a graphite boat and put it into a tubular atmosphere furnace, the inlet and outlet of which are both open, and introduce helium into the tubular atmosphere furnace, the volume of which is twice the volume of the tubular atmosphere furnace.

[0041] Step 3: Turn on the heating mode of the tubular atmosphere furnace, heat up to 400°C at a heating rate of 8°C / min, keep warm for 40 minutes, then heat up to 580°C at a heating rate of 8°C / min, keep warm for 60 minutes. Only during the heating process, introduce hydrogen into the tubular atmosphere furnace with a hydrogen flow rate of 6L / min.

[0042] Step 4: Subsequently, the heating is stopped and helium is introduced into the tubular atmosphere furnace. After cooling to room temperature, the material is taken out to obtain the finished product of antimony tritelluride.

[0043] Example 3

[0044] Step 1: Weigh Te powder and Sb powder according to a molar ratio of Te to Sb of 3.08:2, mix them evenly in a xenon atmosphere to obtain a mixed material.

[0045] Step 2: Place the mixed powder in a graphite boat and put it into a tubular atmosphere furnace, the air inlet and outlet of which are both open, and introduce xenon gas into the tubular atmosphere furnace, the volume of which is twice the volume of the tubular atmosphere furnace.

[0046] Step 3: Turn on the heating mode of the tubular atmosphere furnace, heat up to 380°C at a heating rate of 8°C / min, keep warm for 30 minutes, then heat up to 550°C at a heating rate of 8°C / min, keep warm for 90 minutes. Only during the heating process, introduce hydrogen into the tubular atmosphere furnace at a hydrogen flow rate of 5 L / min.

[0047] Step 4: Subsequently, the heating is stopped and xenon gas is introduced into the tubular atmosphere furnace. After cooling to room temperature, the material is taken out to obtain the finished product of antimony tritelluride.

[0048] Example 4

[0049] It is basically the same as Example 1, except that in step 3, the heating rates of the first heating and the second heating are both 10°C / min.

[0050] Example 5

[0051] It is basically the same as Example 1, except that the heating rates of the first heating and the second heating are both 5°C / min.

[0052] Example 6

[0053] The method is basically the same as Example 1, except that in step 3, carbon monoxide is introduced during the heating process to replace hydrogen.

[0054] Comparative Example 1

[0055] The method is basically the same as Example 1, except that in step 3, xenon gas is introduced during the heating process to replace hydrogen gas.

[0056] Comparative Example 2

[0057] The method is basically the same as Example 1, except that in step 3, heating is performed to 550° C. at a heating rate of 10° C. / min.

[0058] Comparative Example 3

[0059] It is basically the same as Example 1, except that in step 3, the heating rates of the first heating and the second heating are both 60°C / min.

[0060] Comparative Example 4

[0061] The method is basically the same as Example 1, except that in step 1, Te powder and Sb powder are weighed at a molar ratio of Te to Sb of 3.05:2, and the mixture is uniformly mixed in an inert gas atmosphere, and the mixed Te and Sb mixture is compacted to obtain a mixed material.

[0062] Comparative Example 5

[0063] The process is basically the same as Example 1, except that the molar ratio of Te to Sb in step 1 is 3.5:2.

[0064] Comparative Example 6

[0065] The method is basically the same as Example 1, except that the molar ratio of Te to Sb in step 1 is 3:2.

[0066] Test method:

[0067] Use Energy Dispersive Spectrometer (EDS) to test oxygen content

[0068] Table 1: Performance test results

[0069]

[0070]

[0071] Result analysis:

[0072] 1. It can be seen from Examples 1-3 that when the flow rate of hydrogen is gradually reduced, the oxygen content of antimony tritelluride gradually increases and the purity gradually decreases. It is not difficult to see that the hydrogen flow rate is inversely proportional to the oxygen content of antimony tritelluride. We speculate that due to the increase in the flow rate of hydrogen, the contact amount of antimony tritelluride with hydrogen per unit time will increase, resulting in the reduction of tellurium oxide and antimony oxide impurities in antimony tritelluride, thereby reducing the oxygen content in the raw material, and then reducing the oxygen content of antimony tritelluride. However, from the perspective of actual production, although there is a certain gap in the oxygen content between Examples 1-3, considering that different products have different requirements for the oxygen content of antimony tritelluride, and under normal circumstances, the purity of antimony tritelluride in Examples 1-3 is within an acceptable range. Therefore, out of consideration of production cost, we recommend that the flow rate of hydrogen is 4-6L / min.

[0073] 2. It can be seen from Example 1 and Examples 4-5 that as the heating rates of the primary heating and secondary heating decrease, the oxygen content of antimony tritelluride gradually decreases. The reason may be that the heating rate decreases, resulting in a prolonged heating process, which in turn results in a prolonged contact time between hydrogen and antimony tritelluride, thereby reducing the oxygen content of antimony tritelluride. However, from the perspective of actual production, the difference in oxygen content between Examples 4 and 5 is not large, and the heating rate of Example 4 is lower, which results in a higher production cost for Example 4 than for Example 5. Therefore, out of consideration for production cost, we recommend controlling the heating rate between 6-9°C / min.

[0074] 3. It can be seen from Examples 1 and 6 that using carbon monoxide, which also has reducing properties, instead of hydrogen can also inhibit the oxygen content of antimony tritelluride. However, due to the toxicity of carbon monoxide itself, we recommend using hydrogen to inhibit the oxygen content.

[0075] 4. It can be seen from Example 1 and Comparative Example 1 that using an inert gas without reducing properties instead of hydrogen cannot reduce the oxygen content of antimony tritelluride.

[0076] 5. It can be seen from Example 1 and Comparative Example 2 that in step 3, after using one heating instead of multiple heating, the antimony content in antimony tritelluride is too high. We speculate that the reason is that the oxygen content mainly comes from tellurium oxide and antimony oxide after oxidation and deterioration. It is necessary to remove oxygen as much as possible before they reach the reaction temperature. Once the compound is synthesized, the internal oxygen is difficult to remove.

[0077] 6. It can be seen from Example 1 and Comparative Example 3 that in step 3, when the heating rate is 60°C / min, the heating process is too short and the heating is too fast, which can easily lead to incomplete reaction of tellurium and antimony. At high temperatures, tellurium volatilizes due to vapor pressure, which makes the antimony content in antimony tritelluride too high.

[0078] 7. It can be seen from Example 1 and Comparative Example 4 that the antimony content of antimony tritelluride prepared using compacted tellurium powder and antimony powder is too high. We speculate that the reason is that the reaction after compaction is relatively violent, generating a large amount of heat, causing tellurium to volatilize.

[0079] 8. It can be seen from Example 1 and Comparative Examples 5 and 6 that when the tellurium content is increased, antimony tritelluride with a lower oxygen content is obtained, but the free tellurium in the product is too much, which, on the one hand, causes the impurity content in antimony tritelluride to be too high, and on the other hand, too much tellurium powder is wasted, and the production cost is too high;

[0080] When the molar ratio of tellurium to antimony was 3:2, the antimony content in the obtained telluride was too high. We speculate that the reason is that part of the tellurium did not react, resulting in an excessively high antimony content.

Claims

1. A method for preparing antimony tritelluride, characterized in that: The following steps are involved: Step 1: Weigh Te powder and Sb powder according to the molar ratio of Te to Sb being 3.05:2, and mix them evenly in an inert gas atmosphere to obtain a mixed material; Step 2: Place the mixed material in an inert gas environment; Step 3: heating the mixed material in sections; Step 4: Cooling the mixed material to obtain antimony tritelluride finished product; Step 3 is specifically as follows: turning on the heating mode of the tubular atmosphere furnace, heating the temperature to 350°C at a heating rate of 10°C / min, keeping the temperature for 45 minutes, and then heating the temperature to 550°C at a heating rate of 10°C / min, keeping the temperature for 80 minutes; And during the heating process of step 3, hydrogen is continuously introduced, and the flow rate of hydrogen is 4-10 L / min.

2. The method for preparing antimony tritelluride according to claim 1, characterized in that: Step 2 is specifically as follows: placing the mixed material prepared in step 1 in a graphite boat, and placing it in a tubular atmosphere furnace, while opening the air inlet and air outlet of the tubular atmosphere furnace, and continuously introducing inert gas, wherein the volume of the introduced inert gas is 2 to 3 times the volume of the tubular atmosphere furnace.

3. The method for preparing antimony tritelluride according to claim 1, characterized in that: Step 4 is specifically as follows: introducing an inert gas into the tubular atmosphere furnace and exhausting the reducing gas in the tubular atmosphere furnace, cooling to room temperature, taking out the material, and obtaining antimony tritelluride.

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